Piston-deck height

Deck height is defined as the distance between the top edge of the piston crown (with the piston at TDC) to the edge of the cylinder liner. The closer the edge of the piston crown is to the edge of the cylinder the high the compression ratio will be.

So if you have pistons that are 10.5:1 and they are 0.010″ below the edge of the cylinder and you are able to reduce the deck height by 0.010″ then the actual compression ratio of the cylinder will be increased.

The reduction of the piston deck height can be accomplished in several ways. Machining the cylinder block is the most common method.

A word of caution you must know exactly the minimum valve to piston clearance that is required. this varies in different engine designs. To increase the piston to valve clearance usually the valve relief pockets on the piston’s crown are enlarged or the height of the piston at TDC must be lowered in the cylinder.

Oversize Valves

Some tuners believe that larger size valves enhance Hi-RPM power at the expense of Low-RPM power. This has proven to be false due to the results of dyno tests and theory. Larger valves enhance Hi and Low RPM.

When a valve is closed it has no size whatsoever for a cylinder’s ability to induce air flow. A valve that is opened, 0.015”, appears to the cylinder as a small valve. Only when the valve reaches 25% of its total lift point does the cylinder actually experience anything near the true size of the valve. If a cylinder was stuffed with valves as big as possible to create a greater movement of the air/ fuel mixture and exhaust gasses and the larger valves proved to be excessive (too large), the solution of the problem would be to reduce the valve’s lift, besides reducing the air flow it would also reduce the wear and friction on the valve train. In the real world, the criterias for the intake and exhaust system for making peak HP and torque at a given engine RPM is the cross section area of the intake and exhaust ports, not the size of the valves.

The real advantage of using oversize valves is that, for a specific rate of the valve’s opening, an oversize valve will give a greater breathing area to the cylinder quicker. This is equal to as a smaller valve opened at higher rate of acceleration. Any time there is a higher acceleration rate in the valve train, more stress is created.

As long as valve shrouding is not a factor then the largest possible valve in a cylinder head will allow the engine to develop power over the widest RPM range, not just increase the flow at high lift rate. If a dyno test of a engine with a cylinder head that has oversize valves reveals a loss in low RPM power it is because the engines camshaft has to much overlap.

For carbureted normally aspirated Suzuki engines in the 9.5 to 12:1 compression ratio range the exhaust flow needs to be 75 percent of the intake flow. Overall when the compression ratio of an engine increases, in order to obtain the maximum results an exhaust valve can be made smaller in relation to the intake valve. This is due to the power developing earlier in the expansion cycle of a cylinder in high-compression engine, thus allowing the exhaust valve to be opened sooner and longer without any problems. A small exhaust valve will create the opportunity to use a larger intake valve.



If you read my previous post about ‘AIR DENSITY’ in this thread then it will be easy to understand the advantages Nitrogen has over Air, for those who haven’t, I would recommend to do so.

The first advantage of Nitogen is for it’s use in your tires, by doing so you will eliminated tire pressure build up, this is a really important factor in order to maintain a tire’s performance criteria. The Racing Displines of Road Racing or Drag Racing require consistency of a tire performance and the use of Nitrogen will give you that advantage.

In Drag Racing when using an ‘Airshifter’, the use of Nitrogen will add the the unit’s reliability ( No Water contained in Nitrogen) and you will find that the shifter activation responce time is faster.

Longer exhaust duration

Most stock camshafts from production 4 cylinder engines manufactured today are ground with the longer exhaust lobe duration,or that they are ground with shorter intake durations. This can be viewed that either the Exhaust Ports or Exhaust Pipe system is somewhat restrictive, and needs assistance, or that the intake system is very efficient and cam timing can be trimmed back without a sacrifice in power, in order to maximize throttle response and cruising efficiency. There is no absolute correct viewpoint in a stock engine running at conservative RPM levels, for the sake of overall efficiency, fuel economy and a quiet smooth running engine, this staggering of intake and exhaust duration is quite common and appropriate.

High Performance is another thing entirely. Change one factor, such as the exhaust system installing headers and larger pipes and the need for that longer exhaust lobe has been eliminated. Now add to this change a different carb system and camshaft and you have really changed the equation. But, why is it that so many racers & cam grinders insist on running a cam with longer exhaust duration regardless of what equipment is used? The answer is habit, many have been somewhat successful in doing it this way and will never change unless forced by circumstances.

The best result comes when we realize that an engine is basically an air pump. Air is pumped in and out and there are problems when one side or the other is restricted. Balance and flow is our objective, unless you are NOT trying to make more horsepower!

Most experienced Tuners run a single pattern cam, equal on intake and exhaust duration. This type of designed cam always make more torque.

Intake & Exhaust Port Surface Finish

As long as the intake port surface finish is fine enough so that the highest protrusions are not above the air /fuel mixture boundary layer thickness, then improvements on the finish will have little effect on air / fuel mixture flow . A rougher finish is actually an advantage. Do not over polish an intake port because of its wet fuel flow capability.

A polished exhaust port will increase the exhaust gas flow and will reduce the potential for carbon to build up on the exhaust port surface.

In conclusion 97% of a performance gain from porting a cylinder head is from the shape of the ports and only 3% is from a polished finish.

Induction System Volumetric Efficiency

here are two real world effects that determine how much fuel/air charge can get into the cylinder. The first is that air is compressible, the second is the dynamics (acceleration/deceleration) of the air. The compressibility of the air becomes a factor when the air enters the intake port around the intake valve. The intake port/valve forms a constriction, like the throat of a nozzle. Because air is compressible, it can only be pushed through a constriction so fast. Regardless of how much pressure you apply, the maximum velocity possible through the throat of a nozzle is a velocity equal to the speed of sound .

The same effect happens at the intake valve. The ratio of the typical velocity to the intake sonic velocity is called the inlet Mach index. From the science of fluid mechanics the controlling velocity in a compressible flow system is usually the intake valve opening. For a given cylinder and valve design, the inlet Mach index is proportional to the piston speed, and that the fuel/air charge flows in faster when the piston moves down faster. Of course, at some point the constriction of the valve opening starts to limit this. When the inlet Mach index exceeds 0.5 (intake velocity equal to half the speed of sound), the volumetric efficiency falls rapidly with increasing speed. Therefore, enginest are typically designed so that the inlet Mach index does not exceed 0.5 at the highest rated speed.

The effect of this constriction shows up as a pressure drop through the intake valve. Why don’t we just open the intake valve further? Because when the valve is lifted a distance equal to 1/4 of its diameter, the area of a cylinder around the valve (that the fuel/air charge passes through, not the engine cylinder) is equal to the area of the valve face and intake port, ignoring the valve stem. Mathematically, the area of the cylinder is (2 r)(d/4). Since d = 2r, this evaluates to r2, which is the area of the intake port, the amount of additional flow through the intake port increases very slowly as the lift of the valve increases beyond 1/4 of the valve diameter.

Because of the dynamics of the fuel/air charge, the intake valve normally closes at some time after the piston passes bottom dead center. As the piston moves down, it draws the fuel/air charge into the cylinder. This movement builds up momentum in the intake manifold. When the piston reaches bottom dead center, the fuel/air charge is still flowing into the cylinder as a result of this residual momentum. Thus, at the speed desired for maximum torque, the intake valve closing is timed to correspond with the velocity of the fuel/air charge through the intake port dropping to zero. This closing will occur at some time after the piston has started the compression stroke, and will result in the maximum amount of fuel/air charge being drawn into the cylinder. This maximizes the volumetric efficiency, and maximizes the torque delivered to the crankshaft, ignoring friction effects. The angle of the crankshaft at the time the intake valve closes is called the intake valve closing angle.

So what effects does this later valve closing have at other speeds? At low speeds, the momentum built up in the intake manifold will be small, such that part of the fuel/air charge will be pushed back into the intake manifold as the piston starts up prior to the intake valve closing. At speeds above the speed for maximum torque, the constriction of intake valve opening will cause a pressure loss which will reduce the amount of fuel/air charge entering the cylinder. In either case, the amount of fuel/air charge in the cylinder is reduced, and thus the torque is reduced.

The design of the intake manifold also affects the amount of momentum built up in the flow of the fuel/air charge. The momentum of the fuel/air charge is the sum of the effect of standing waves built up from previous intake strokes keep in mind that any tube will have a resonant frequency and effect the transient wave caused by the current intake stroke. While the standing waves contribute to the overall effect, there are no sudden changes in the volumetric efficiency when the RPM of the engine is an even multiple of the natural frequency of the intake manifold.

Long, skinny intake manifold pipes give high volumetric efficiencies at low piston speeds because high momentum lots of velocity is built up in the pipe during the intake stroke. At high piston speeds, the small diameter of the intake pipe causes a constriction and the volumetric efficiency falls. Fat intake pipes show a maximum volumetric efficiency at intermediate piston speeds. However, at high piston speeds, the larger mass of the fuel/air charge in the fat intake pipe is slow to accelerate, and thus the volumetric efficiency falls off.

As the manifold pipes get shorter, the maximum gain in volumetric efficiency over having no intake manifold at all decreases. However, the gain you do get with shorter intake pipe happens over a greater range of piston speeds. Basically, it comes down to the intake manifold pipe should be designed according to the engine requirements. If you need high torque at slow piston speeds, use long skinny intake pipes. For high torque at intermediate piston speeds, use long fat intake pipes. For high torque over a wide range of piston speeds (i.e. a flat torque curve), use shorter intake pipes.

Ignition components

Inductive Discharge Coils – Ignition spark for motorcycle is accomplished by the iginiton coil, coils have 2 sets of windings, a primary and a secondary. A typical coil will have around 250 turns of wire on the primary and about 25,000 on the secondary for a ratio of 100 to 1. The secondary section often uses an iron core to increase its inductance. Coil resistance on the primary will be from .3 to .5 ohms usually and on the secondary, between 5000 and 12,000 ohms. The inductance and resistance of the coil will determine how quickly a coil can be charged and discharged.

A transistor is used to switch the current flow off and on in the primary coil. When the transistor is switched on, current rapidly builds from 0 to a maximum value determined by the coil inductance and resistance. This current flow induces a magnetic field within the primary. When the current is turned off, this magnetic field collapses which cuts the windings of the secondary coil and induces a high voltage surge.

Output voltage is determined by the rate of field collapse and the windings ratio between primary and secondary. Because the path to ground for the current involves the spark gap, initial resistance is extremely high. This allows the voltage to build to a high value until it gets high enough to jump the plug gap. The difference must be high enough to first ionize the gas between the electrodes. The ionized gas creates a conductive path for the current to flow, at this point the arc jumps and current flow is established.

If only 10,000 volts are required to jump a plug gap under a given condition, that will be the maximum delivered. It is also important to note that the spark duration is determined by coil inductance and total resistance of the circuit, plus spark plug gap. Most inductive discharge systems have a spark duration of between 1 and 2 milliseconds.

When cylinder pressure increases, the voltage required to jump the plug gap increases. The second problem on high performance engines with high rev limits, is that there is less time to charge the coil with increasing rpm, high rpm and high output puts greater demands on the ignition system.

Coil Charge Time and Saturation – The time it takes to charge the coil or bring the current to maximum in the primary windings is called charge time. Input voltage and coil resistance are the main parameters relating to charge time, when the current has reached its maximum value in the primary, it is said to be fully saturated.

If current is applied longer than the time needed to fully saturate the primary, energy is wasted and there is nothing to be gained. If the current is cut off before saturation is achieved, the maximum spark energy available will be reduced.

Coils require charge times of between 2.1 and 6 milliseconds. Obviously, a coil requiring 6 milliseconds to saturate would be unsuitable on a high revving engine as there is not 6 milliseconds available to charge it between discharges at high rpm. For this reason, most racing coils have low primary resistances between .3 and .7 ohms and are fully saturated in less than 3 milliseconds permiting full coil output at very high rpms.

Capacitive Discharge Ignition – On very high output engines, an inductive discharge coil is inadequate to supply spark at high rpm and high cylinder pressures. A CD ignition or CDI is used to reduce charge times. The MSD system is very popular worldwide.

In normal inductive discharge coils, only 12-14 volts is available from the battery to charge the primary. The CDI charges capacitors to store a high voltage kick to fire to the primary side, putting between 30 and 500 volts onto the primary windings which reduces the charge time substantially. A coil that would take 3 milliseconds to become fully saturated with 12 volts is now fully saturated in less than 1 with a CDI. The same engine now will be able to turn twice the RPM and experience a major increase in cylinder pressure before encountering misfire.

Some CDIs also include a multispark function where more than 1 spark is generated after the first spark. This improves ignition probability besides the high rpm coil saturation advantages and a greater resistance to plug fouling.

Ignition Wires (Spark Leads) – The purpose of the ignition wires is to conduct the maximum coil output energy to the spark plugs with a minimum amount of radiated electromagnetic interference (EMI) and radio frequency interference (RFI). There are 3 basic types of conductors used in racing applications: carbon string, solid and spiral wound. Most production engines come equipped with carbon string. The solid core types are used exclusively for racing, mainly with carbureted or non-computer controlled engines because they offer no EMI or RFI suppression. They generally have a low resistance stainless steel conductor. These types are rapidly losing favor, even in racing circles.

The carbon string type is the most common and work just fine in racing applications. The conductor is usually a carbon impregnated fiberglass multistrand. Suppression qualities are fine with resistances in the 5K to 10K ohms per foot. They are cheap and reliable for 2 to 5 years usually, then they may start to break down and should be replaced. High voltage racing ignitions will likely hasten their demise. Dynatech makes low priced wire set which works well in performance applications.

Ignition Wires (Spark Leads) – The spiral wound type is probably the best type for any application. The better brands offer excellent suppression, relatively low resistance and don’t really wear out. Construction quality and choice of material vary widely between brands. NGK makes low priced wire sets which work well in performance applications.

Some amount of resistance is required along with proper construction to achieve high suppression levels. Resistance is also important to avoid damaging some types of coils and amplifiers due to flyback and coil harmonics. Beware of wires claiming to have very low resistance. These CANNOT have good suppression qualities.

Beware of any ignition wires claiming to increase hp. Ignition wires CANNOT increase hp. As long as the wires that you have are allowing the spark to jump the gap properly, installing a set of $200 wires is strictly a waste of money.

Lately, some truly “magic” wires have come onto the market claiming to not only increase power but also to shorten the spark duration from milliseconds to nanoseconds. As previously mentioned, spark duration is determined primarily by coil inductance and coil resistance so these wires CANNOT shorten the spark duration by the amount claimed. The wire resistance has a minimal effect on discharge time because of the high voltage involved. A very short duration spark is in fact detrimental to ignition because of lower probability.

These same wires claim to increase flame front propagation rates and the ability to ignite over-rich fuel mixtures for more power. Once ignited, the mixture undergoes a flagregation process and that the progression rate of the flame front is totally independent of the spark. As previously mentioned most gasolines will not ignite nor burn at air fuel ratios richer than 10 to 1, period, and that maximum power is actually achieved at around 12 / 13 to 1 AFR so the claim also has no basis in fact.

These wires use a braided metal shield over the main conductor which is grounded to the chassis. This arrangement offers poor suppression because it does not cover the entire conductor. Any energy leaking out of the main conductor by induction is actually wasted to ground and will not make it to the spark plug. These wires also have very low resistance which as mentioned can have a detrimental effect on coils and ignition amplifiers due to severe flyback effects which are normally damped by circuit resistance.

Other claims for these wires include current flows of up to 1000 amps. The current flow in the ignition circuit is determined by the coil construction and drive circuits, not by the ignition wires. Most ignition systems are current limited to between 5 and 15 amps. The most powerful race systems rarely exceed 30 amps. To flow current at 1000 amps, you would require #0 welding cable for the ignition system!

Spark Plugs – The final part in the ignition system is the spark plug itself. The average plug consists of steel shell which threads into the cylinder head, a ceramic insulator, an iron or copper core leading to a nickel or platinum center electrode and a ground electrode of similar material. The spark jumps between the center and ground electrode. Certain special application plugs may have multiple ground electrodes. Different heat ranges are available depending on application. For constant high power applications, a colder than stock plug is usually selected to keep internal temperatures within limits.

Again, many “trick” plugs come onto the market from time to time expounding the virtues of their incredible new design, usually offering more hp of course. Split electrode plugs are a waste of money because the spark will only jump to one of the electrodes at a time in any case.

You will find that most reputable engine builders for racing use standard NGK, Bosch or Champion plugs with a standard electrode setup. A properly selected, standard plug will easily last 25,000 miles of hard use in most engines. A platinum tipped plug will easily last twice as long on most engines. There is no rocket science here, modern spark plugs coupled to modern ignition systems in a modern engine are extremely cheap and reliable, even on race engines, a $2, off the shelf, NGK plug will work just fine.

Ignition / combustion criteria

Some people think that when a spark plug fires, the fuel/air mixture explodes instantaneously, driving the piston down. If this really happened, engines would last only a few minutes before they literally explode.

Looking at the dynamics involved from the moment that the intake valve is fully open. With the piston moving down the bore, cylinder volume increases, cylinder pressure decreases, allowing the higher pressure in the intake tract to push the fuel/air mixture into the cylinder. As the piston starts back up and the intake valve closes, cylinder volume decreases and cylinder pressure increases.

When the crankshaft reaches about 30 degrees before top dead center (TDC), the spark jumps the gap between the spark plug electrode. The purpose of the spark is to raise the temperature of a very small portion of the fuel/air mixture above its ignition temperature. This is the point where true combustion begins. As the reaction starts, the mixture directly adjacent to the spark plug is also ignited and the process progresses out from the spark plug in a roughly spherical shape.

At about 20 degrees before top dead center (BTDC), the rate of heat release causes the cylinder pressure to rise above the compression line which is what the cylinder pressure would be at a given piston position without ignition. Notice that it has taken 10 degrees of crank rotation to generate this pressure level. This is known as the ignition-delay period.

The rate of pressure rise is a function of the rate of energy release vs. the rate of change of combustion space. The rate of energy release is directly related to the flame propagation rate and the area of reacting surface. The flame speed is dependant on fuel/air ratio, charge density, charge homogeny, fuel characteristics, charge turbulence and reaction with inert gasses and the combustion chamber, cylinder walls and piston.

No two combustion cycles progress at the same rate or uniform rate. Some start slow and end slow, some start slow and end fast, some start fast and slow down. Generally, only the ones that end too fast will lead to detonation / knocking / pinging as the rapid pressure rise may happen too soon with the cylinder volume still decreasing or not increasing fast enough. Usually, not all cylinders will detonate / knock / ping at the same time or on the same cycle because of this.

By the time the crank is at about 5 degrees after top dead center (ATDC), the cylinder pressure is about double that of the compression line. From this point to roughly 15 degrees after top dead center (ATDC) the combustion process is fast due to the increasing area of inflamed mixture and the high rate of energy release. The peak cylinder pressure (PCP) occurs between 10 and 20 degrees after top dead center (ATDC) on most engines and the combustion process is complete by 20 to 25 degrees after top dead center (ATDC). The peak temperature within the combustion gasses will reach somewhere around 5000 degrees Fahrenheit and pressures may be anywhere from 300 to 2500psi depending on the engine.

Obviously it is very important to have the crankpin at an advantageous angle before maximum cylinder pressure is achieved in order that maximum force is applied through the piston and rod to the crankshaft. If the mixture was ignited too early, much of the force would simply try to compress the piston, rod and crank without performing any useful work. In a worst case scenario, the cylinder pressure would be rapidly rising before the piston reached top dead center (TDC) which would have the cylinder volume decreasing at the same time. This will often result in detonation/knock/ ping which is counterproductive to maximum power and engine life.

Detonation, knock or pinging is defined as a form of combustion which involves too rapid a rate of energy release producing excessive temperatures and pressures, adversely affecting the conversion of chemical energy into useful work. Detonation usually involves ignition and literal explosion of the end gases, these are the gases not in contact with the initial spark or the progressing flame front.

If peak cylinder pressure (PCP) is achieved too late, again, less work would be performed. Most of the useful work is done in the first 100 degrees of crank rotation. Most combustion must be done with the piston in close proximity to the chamber so that the minimum amount of heat (energy) is lost and the maximum amount of energy is delivered to the crankshaft.

Frankenstein’s guide to oil cooled engines

Before anything, I would like to have it said that I wrote this in my best knowledge and do
not want to be held responsible for any mistakes. I’m confident about what I’ve seen and done,
but since I’m not the only one messing around with gixxers, I can hardly ever be sure that
the engine I find in a 89 1100R is really an 89 1100R. I’ve left the types before 88 out,
since I have not much experience with them.


There are mainly 2 types of 750’s, the 88-89 short stroke, and the pre-88 and 90-91 long stroke.
(The 750F is basicly the same motor as the 88-89 short stroke, the B6 and GSXF600 are basicly
the same as 90 long stroke with a smaller bore).
1100R motors from 88-92 are similar to the 1100F and B12 motors. The 1100G is also similar,
but has an axle drive. They all have the same stroke, and only the B12 has a 1mm bigger bore.

Apart from the color, all the GSXR, GSXF, GSXG and Bandit ignition covers are the same (except
the 750RK).

The clutch covers are depending on the clutch operation, there are 3 possibilities:
(The dry clutch is left out, to avoid making it more confusing).
1.The GSXF600, GSXF750 and B6 have the clutch cable connected to a mechanism on the sprocket
cover, and the clutch is operated by a push pin through the primary gear box shaft.
2.The 750R has the clutch mechanism in the clutch cover (on the right side). The 88-89 clutch
cover is recognizable by a smooth clutch cover, the 90-91 has a bubble in the center. They are
very similar, but since the engines have a different clutch, I don’t think these covers can be
swapped, I haven’t tried though.
3.The 1127’s and B12 all have the clutch mechanism on the sprocket cover, like the 600’s and
the 750F, but then hydraulically operated. The mechanisms on the sprocket cover can all be
swapped, so it’s possible to put a cable operation from a B6, F6 or F750 on an 1127 (and v.v.),
although it might need some adjustment of the length of the pushrod.
This also means that, since the clutch covers on the 600’s, 750F and 1127’s are nothing but
covers, they can be swapped.

The startermotor covers from the 1127’s are all the same (The startermotor covers from the 1052
engines are not the same) The 1127 covers can be recognized by a kind of bubble, to accomodate
the bigger starter motor. The 600′ and 750’s have a smaller starter motor, and the top line of
these covers is straight. (I believe the 1052 motors also have this smaller starter motor and
cover). Covers can be swapped among the 600’s and 750’s, but an 1127 cover only fits an 1127.

The oil pan on all 1127’s are the same, but the B12 is different. The 750F and 750R 88-89 have
the same oil pan as the 1127’s. The 91-750R and B6 have a similar or same oil pan as the B12,
I’m not sure. However, it is possible to swap these oil pans, as long is you change the oil
pickup as well. Oil hoses on the 1127 pans connect at the front, the others at the bottom.

The valve covers are different depending on the cam chain type, and the cylinder head size.
The B6 cover only fits the B6, the B12 cover only fits the B12. The 750R-90 and 91 covers
are the same. All the 1127 and the 750R-88/89 cam covers are the same.

There a 3 main items which make the difference in crankshafts.
1. Stroke
2. Clutch gear
3. Camchain type

1. The 1127’s and B12 all have the same stroke. The 600’s and 90-91 750R’s have the same
stroke. The 88-89 750’s and the 750F have the same stroke.
The stroke is important because this directly reflects on the number on teeth on the
clutch gear (ie. the gear diameter).
2. All GSXR1127 crankshafts are the same. The GSXF and G have a helical
cut gear, so when using a GSXF1127 crank You will have to use a GSXF1127 clutch basket as well.
3. All GSXR’s (both 750 and 1127) have the same type camchain, but the B6 and B12 are
different. Since the cam chain is driven from the crankshaft, this means these crankshafts
are not interchangeable with GSXR crankshafts, unless you also change the cam chain, tensioner,
guides, cam sprockets, cam covers, cam guiding between cam shafts.

All the 3 items above have to match. Swapping a crankshaft with a type that has the same
stroke, clutch gear and cam chain is no problem. If you start mixing, you have to match
clutch to the crankshaft (and in some cases gearbox), or cam chain stuff to the crankshaft.

Connecting rods from B6, 750R-90 and 750R-91 can be swapped. 1127 rods are all the same.
I have used B12 rods in 1127’s; I found there was a minor weight difference, but they could
easily be matched. This difference might have been incidental.

I left out the dry clutches on purpose, since I have no experience with them.

The GSXR1127 89-on and B12 have a diaphragm spring, the GSXF/G have normal springs.
The GSXR and B12 have a straight cut gear, the GSXF/G have a helical cut gear.
Because of the different gear on the clutch basket, the clutch basket is not swappable.
Since the types with a diaphragm spring have a longer shaft to accommodate the bolt for the
central spring, these parts are also not swappable. It is possible to use the internal clutch
parts from a ‘normal spring type’ in the basket (or actually on the gear box shaft) from a
‘diaphragm spring type’, but you need to fill the space on the longer shaft. It is not
possible to use the diaphragm style clutch on a GSXF gear box shaft, since the shaft is to short.

The 88-89 750R have a large (actually the largest) diameter but relatively flat clutch.
Although the gear box shaft is the same, the 88-89 clutch can not be swapped with the 91
clutch because the crankshaft diameter (and consequently tooth count) is different.
Although the B6 clutch is the same diameter as the 91 750R clutch (since they have the
same stroke), there is not a lot to swap there since the plates are different and the
gear box shaft are differently machined.

Cylinders block with pistons from 1127’s can all be swapped. B12 block+pistons fit the 1127
as well, or only pistons+have your 1127 block bored.
88-89 750’s is same as GSXF750.
B6 and 90/91 750R have 18mm wrist pins, whereas 88-89 750R, GSXF750, 1127’s and B12 have
20mm pins.
Since the B6 and later 750R 90-91 have the same stroke, cylinder block dimension, and wrist pin
diameter, the 90/91 block+pistons can be swapped with the B6 stuff (although you’ll have to
check that the pistons don’t hit the head/valves).

The long stroke engines (ie. B6, GSXF600, 90/91 750R) have the same dimensions, just the
combustion chamber and valves in the 750’s is bigger. So somebody who want less power could
fit a B6 top on a 90 750R. Camshaft type on the B6, GSXF600 and 90 750R is forked rocker,
meaning 1 cam for each pair of valves. 91 750R has shim type with 1 cam for each valve.
If swapping the camshafts as well, the 90 and 91 heads can be interchanged.
Both the 90 and 91 750R top ends can be used on a B6, but since the B6 has another type of
camchain, it is needed to maintain the B6 cam chain tensioner, guides, cam sprockets, valve
cover etc.

The 750 short stroke engines 88/89 heads have the same outside dimensions as the 1127/B12,
but the combustion chamber is smaller (although the valves are the same diameter).
The 1127R-91/92 has the same style head as the 750R-91, but
not much to swap; 1100 valve spacing differs (so camshafts can not be swapped), 1100 valves
are bigger, outside head dimensions differ.
As mentioned, 750R-88/89 valves are the same as 1127/B12, exception are the 1127R-91/92 valves.
These heads have shim type adjustment, and therefore different cams and longer valves.

It is possible to modify a 1127 shim head to a forked rocker head. It’s quite some work, and
you’ll need the valves from the forked rocker head, the rockers, cam shafts. You’ll need to
make all the spacers yourself, or in fact I believe there is a company that has or used to
have a modification kit.

Cam shafts from the 1127F, 750F, 90-750R, B6, B12, 88/89 750R are theoretically all swappable,
but of course the profiles are different. The long stroke 750’s have a different tooth count
on the cam sprockets so they can not be mixed. B12 sprockets can only be used in the B12.
B6 sprockets can only be used in the B6. 1127F and 1127R sprockets are the same, 88/89-750R
sprockets are similar, but the timing marks are different. (Meaning they can only be used if
slotted and timed)

1127: Depending on the clutch type there are long and short shafts. Also the gears themsleves
from these boxes are different. It may be possible to swap a few gears between these boxes,
but the gearchanges might not be very smooth.
Apart from the clutch type, the 91-92 1127R has a double row bearing on the output shaft, and
therefore a slightly different crankcase (around the bearing area).

Gear boxes from all 750’s are swapable. I have no experience with swapping gears seperately.

The B6 has a different shaft, so it can only be used with it’s own clutch.

Although it might seem there are so many differences, a lot can be mixed, as long as the right
parts are choosen, a few examples.
(There are some basic guidelines to assemble an engine, like check compression, cam timing, valve
clearance etc., no matter what combo you’re making).

1. A 1052 crank fits in 88-89 750R and 750F cases, but a 1127 crank doesn’t (but the cases can
be modified to take the 1127 crank as well)

2. A 750R-90 or 750R-91 top end on a B6.
It’s actually very easy, and I think all the info you need is above. Both engines have the same
stroke, same wrist pin diameter. Theoretically, it would be possible to put only 750 cylinders
and pistons on a B6. However, the pistons are designed to fit the 750 head and since that also
fits, why not install a 750 head as well (with bigger valves). Since the B6 has another cam chain
the B6 cam chain tensioner, cam sprockets, cam chain guides and B6 valve cover need to be
used. Then there are 2 options: either go for a 750R-90 top end, which uses forked rockers
like the B6 does (so it’s possible to use either the B6 cams or the 750R cams), or go for a
750R-91 top end, which uses another type of rockers so it is not possible to keep the B6 camshafts.

3. A 750R-88/89 top end on a 750R 90/91 bottom end (or 86-87 bottom).
This is a bit more difficult, since it needs some more work and imagination then the plain
assembling of a B6/750.
The 750R-88/89 have a bigger bore, so the idea of this combo is to increase the capacity of the
engine. (You could also take this combo the ‘other way around’, and fit a 90/91 crankshaft + clutch
in a 88/89 engine.)
Since the dimensions of the heads are not the same, it is not possible to only put the 88/89 pistons
+cylinders on the 90/91; the head of the 90/91 would not fit the cylinder block. So the complete
88/89 top has to be installed on the 90/91. The wrist pins on the 90/91 are 18mm, on the 88/89 20mm,
so the small end of the 90/91 rods have to be bored to 20mm. Now the whole thing could mechanically be
assembled, but since the stroke of the 88/89 is smaller, the height of the cylinder block is smaller.
This has to be compensated by putting a spacer under the cylinderblock. (This spacer would very
roughly have to be 1/2 x the difference in stroke, but the only right way is to measure/calculate the

4. 750R 6 box in a 1127 motor
The only hard thing here is to have a hole drilled through the gear box shaft, for the pushrod.
The 750 6 boxes have a single row bearing on the output shaft, and the clutch does
not have a diaphragm spring. So the easiest 1127 engines to put a 6 box in are the ones with a
single row bearing on the output shaft, and no diaphragm clutch, ie. only the GSXF1127 engines.
In these engines the 6 box drops straight in, only the shaft has to be drilled.
Second easy would be an 1127R engine with a diaphragm clutch, but no double row bearing (88-90).
In this case the box would still drop in, but for the clutch one would have to use the inner
clutch parts from a GSXF1127 (with normal springs) and the outer clutch basket from the 1127R
(with a straight cut gear, not helical).
Most work is in a 91/92 1127R where one would have to match the clutch as above + find a
solution for the double row bearing (the solution is actually to turn the double row bearing
inside out, and make a little hole for the small pin).
Of course the shift drum and forks from the 6 box have to be used as well, but they drop in
any 1127 without problems.

5. 88-89 750R head or 750F head on a 1127 or B12
These heads fit as they are, and give higher compression, better ports, larger squish.
In the case of the 91-92 1127R you’ll need to use the 750 camshafts as well, since the
91-92 1127R uses shim type camshafts and the 750 head is forked rocker type. If you use the
91-92 1127R cam shaft sprockets they can be timed as in the manual.
In the B12’s case you could use the B12 or the 750 cams (although they have different profiles)
but will have to use the B12 cam shaft sprockets because of the different cam chain.
In the case of the 88-90 1127R you can use the 750 or 1127 cams, and use the 1127 cam sprockets
(timing ‘by the book’) or use 750 cam sprockets (timing to be done by yourself)


Alternator overcharging problems, oil-cooled engines

Alternator overcharging problems.

Right then ive got to the bottom of this problem and i bet most oil coolers have got this problem thanks to stuart who is a very clever electrical engineer/design.

Suzuki have tried to be clever using a closed loop design which may work when everthing is new perhaps.

Out of alternator are two leads the main power to battery and the other is the ignition feed to alternator which is trigger to turn reg on.
Problem here is voltage drop on the trigger wire, ive measured half volt purely at ignition switch, suppose age takes its toll. ive got further .3 volt loss through wiring and joints i can tell you the connectors are clean and look good.
So alternator battery lead reads say 12.6 volts (engine off) ignition lead reads 12.5 volts but lights on this drops to 11.5 volts where the battery lead reads 12.3 a drop of .8 through switch and harness, so when running when lights are turned on alternator compensator by ramping up output to 15.4 volts which cooks the battery.

Remove ignition feed wire to the alernator and use it to power a relay (switch side) the ignition wire out of alternator straight to positive on battery via the new relay.
Result constant 14.3 volts depending on battery state no matter whats on or off, result.

You have to connect via a relay as the reg would drain the battery in no time as this is trigger to turn reg side of circuit on as its a basic deign not like car 1 wire systems where the actual rotation of alternator triggers it on.

In the past ive destoyed batteries for no reason luckily the powerful little gel battery has lasted 3 years but at least now know the reason why, this has got to affect a lot of bikes this sort of age pointing bto reg when actually its working correctly.
Hope this is of i must also do a right up on cvs and good design change, to stop emulsion tubes wearing out.

Ignition wire from alternator ( to work out which of two wire this is it will be the wire that only has 12 volts on it when ignition is turned on, ie black wire on multi meter to earth red on meter prod each of cables in back of plug)

Cut this wire, the one coming from alternator now connect to positive on battery via a relay.
The other side of cut ignition wire coming out of loom connects to the switch side of this new relay obviously the other side of switch side goes to earth.
So when ignition is off relay is open so connection of battery to ignition wire on alternator and visa versa.

Just one thing: first i tried with a cheap relay, it had a difference of 0,2V on the switched wires, so it charged 14,7V. Then I got a better relay (no difference measurable) and it charges perfectly.