tabby59

Hey Loud, in full racing leathers, helmet, gloves, boots and back protector, I weigh 195lbs. You may want a more specific rate than I do{so far}, I at least wanted to give you an idea of what ball park the rates are in.

OK, I'm back with some spring numbers. Yeah, this is supposed to be an engine thread, oh well. The only number I don't have is the OEM spring rate for the 750. If any of you fellows have that handy, please chime in. The 86-88 1100 OEM spring rate is 6.1 Kg/mm {340 lb/in}. The 86-88 1100 Ohlins shock/spring set {SU 635} uses their 1095-21 spring {180mm long} which is a 7.65 Kg/mm {428 lb/in} rate. So, here you can see how much firmer a spring over OEM Ohlins chose. The 750 Ohlins shock/spring set {SU 5274} uses their 1092-24 spring{170mm long} which is a 8.15 Kg/mm {457 lb/in}. Now you can see why my "seat of the pants" was screaming that the rear end was too stiff when I went to the 1100 linkage. The higher spring rate for the 750 pretty much confirmed to me that the bikes used different leverage ratios in the linkages. Not being a mechanical engineer, and being a bit lazy, I haven't tried to figure out those ratios. I just needed to confirm that there was a difference. I mean,,,,, why would you put a softer spring on a heavier bike if all else was the same? So like I said earlier, I ordered the 1092-21 and 1092-19 {7.14Kg/mm or 400 lb/in}. 1095 is the length {180mm}, 1092 {170mm}. I ordered the one increment softer spring {-19} just in case the actual lighter weight of the bike using the 1100 linkage made the -21 spring a bit too much even.

I haven't dialed in my Ohlins yet to the 1100 spring. Going by the Ohlins spring chart, the 1100 spring is only one of their increments down from the spring used with their 750 shock. So I ordered the 1100 spring and the next increment down from that. That will be my next challenge, to get the 1100 linkage dialed in. I thought I'd just give you a heads up in case the bike doesn't behave like you would expect. Tomorrow I'll dig up the Ohlins numbers so you can have an idea of the rates that I am dealing with. I wouldn't worry about the starter motor or alternator. If they aren't totally toast, they should be fine. I have the original alternator and starter. New brushes and regulator on the alt at about 20K miles. The starter, I cleaned and regreased the bearings and polished the commutator{?}. They both have over 97K miles on them.

When I dropped my motor off at the shop that did the latest version of the motor, the owner{Rick Stetson} and I were talking about bracing. My frame is stock, but I doubled up on all of the mounting plates and eliminated the front rubber bushings. He reaches up on a shelf and hands me that brace. Apparently that was a somewhat popular brace years ago in the drag racing world. I honestly can't say if it made any serious difference,,,, certainly didn't hurt. I've considered more bracing, the usual stuff you see, but at my riding level, even on the track, she doesn't misbehave at all. I got my head off e-bay surprisingly enough. Everything was in good shape. The pistons in the 907 kit were made for 13.5cr. We both thought that was too high for practical street use and I wanted it to run fuss free on 93 oct. pump gas. So he took about .060" off the tops of the pistons. Compression is in the 11s. The head really looks like it was made for bigger valves and they put seats in for smaller intakes{27mm}. I could see and feel a small undercut in the head casting behind the seats. Rick also unshrouded the valves {massaged the chambers}. I have an 1100 linkage also, but with an Ohlins shock. The 1100 linkage has a different leverage ratio than the 750 and amazingly enough the spring rate that came with Ohlins is too stiff with that linkage. I looked up the spring rates of the Ohlins shocks that were made for the 750 and the 1100, and the 1100 does indeed use a softer spring.

Well, I'll tell you what I did to my 86 750. I currently have 907 kit, Carillo rods, lightened balanced and polished crank, lighter starter clutch, RS38s, a fully ported 90 head with 28.5mm intake valves, Mega-Cycle/Yoshimura cams/springs, Hindle 4-2-1 exhaust, and a Dyna 2000 ignition. 142rwhp @ 12K rpm. Revvy? Yes. It scoots right along. I am the original owner and over the years when I get the itch, it gets more mods. It is really a simple question of how much you want to spend. If you look me up on Facebook{Tab Burgess}, look in my photo section. I have posted my dyno sheets and 1/4 mile time slips. It certainly isn't the be all, end all of old GSXRs, just my baby that I'll never sell.

When I went to the 17s, that was the size I started with. I had also made an eccentric bushing for my Ohlins shock at the same time. It allowed me to raise the rear over 3/4s of an inch. Between that and the 17s it steers like a dream. Much less effort than the 18s and even more stable.

What is the rear rim width on your 90? I have an 86 Slabby with 17" Dymags {3.5F, 5.5R} and I have no problems running a 180/55 on the rear. So far I have run Michelin PPs, PP/2CTs, and now Power SuperSports.

I took the stock ignition rotor on both my 86 750G and my 93 GSX1100G and milled the slot on the back to give it 5 more degrees. I set the rotor up with a collet holding indexing head on a bridgeport mill. The head holding the collet conveniently could be indexed in 5 deg. increments. The collet I used had a hex hole nearest to the size of the hex on the rotor So I indicated the slot into the Y axis of the mill. Then I lightly touched off on the side of the slot using the X axis, then locked the table. I then indexed it one 5 deg. increment. Yes, you have to positively know which side of the slot to mill, and yes you should use an endmill that is smaller than the slot. When you are done, you install it with the pin in the crank against the part of the slot you milled. The cool part is, if you want stock timing back, just put the pin against the other side of the slot. Since the slot is at a very small diameter, a 5 degree index doesn't take off much metal. Just another option to consider.

Yup, cartridge emulators here also.

It would be far easier to just get the sliders from the 87H. I'd even go so far as get the ones from the 1100, which I did. Along with the 17mm bore for the axle, the fender mount/fork brace lugs on the 1100's sliders are thicker than the 750s and use the next size up bolt. So if you use a thicker, proper, fork brace,,, as I did, you end up with a stronger "box" so to speak. Be aware though, the the anti-dive unit mounting points are not identical. If you use the 750s anti-dive units on the 1100 sliders, it WILL leak. The o-ring sealing surface locations are not exactly the same. So, use the 1100's units, or block off units for the 1100,,,,, which I did.

Larger CVs should be more forgiving anyways. They aren't a bigger carb until the vacuum slide is pulled completely out of the way.

I have 310mm EBC ProLites discs and their HH pads on my 86 750 slabby. I am also using 86 1100 OEM calipers for the 5mm extra offset for the larger discs. With braided SS lines, it is a very nice set up.

If it is any help, I have a 90 head{long stroke} on my 86 750/907 Slabby{long stroke}. To put it simply, the long stroke 750s {48.7mm} can share heads. Mine has been well modded with full porting to match the 28.5mm intake valves, upgraded from the OEM 27mm intakes. As an FYI, the oem seats will take the 28.5mm valves with no problems.

I am currently using my original OEM "cct" on my 86 well modded 907. In talking with Rick Stetson {Google him}, who built this version of my engine, he recommended using the OEM cct over a manual. I asked about OEM cct failures I had heard about years ago, and he told me that was an issue with the older style cct type on heavily modded GS motors, not the GSXR type. He also told me that the OEM cct is made to have some temperature flexibility. That's the purpose of the short spring on the end of the plunger. I had an APE type manual cct on the 883 version of my 750, but I put that in there based on the older issue that I wasn't fully understanding. No fuss, no muss using the OEM cct!

I'd go with the Bandit pipe. Keep an eye out for a Hindle version. The Hindle blew my Supertrapp right off the dyno. Besides good dyno runs, Hindles are nice because the mufflers are all virtually the same. You can go with a shorty or go with a longer Stealth, and they show up on Eblag fairly often

OK, here is a little of what I've found out. I haven't found the OEM spring rate for the 750. What I did confirm was that the 85-87 750 and the 86-88 1100 indeed do have different leverage ratios in their linkages. What the actual ratios are, I don't know,,, and I'm not a mechanical engineer. I did some cross referencing with Ohlins shocks. They were nice enough to send me some info. 1986-88 GSXR1100 Shock - SU 635, Spring - 1095-21 Rate for the 1095-21 spring: 7.65 Kg/mm {428 lbs/in} 1985-87 GSXR750 Shock - SU 5274, Spring - 1092-24 Rate for the 1092-24 spring: 8.15 Kg/mm {457 lbs/in} So yes, the lighter 750 DOES use a heavier spring than the 1100. That would indicate a different ratio in the linkage. If you make the swap, put the 1100 linkage in the 750, and it doesn't feel right or a lot different, now you may have an idea why. I am going to try the 1092-21 and 1092-19 springs to see if they will be a better combination for this bike.

If your 1100 based engine is anything like my 86 750, you could put the motor together with the shift forks and drum left out. I've changed my drum and forks with the engine IN the frame. The drum and shift fork shaft will go in on the clutch side, while the forks can be put in from the bottom with the pan removed. Not super easy, but far from hard.

Camshaft had asked for this info, or pictures for the eccentric bushing I had made for my Ohlins shock. I'm sorry I don't have any pictures available yet, but I'm sitting here with my dial calipers, so I'll measure things up. Please understand that these numbers are being generated with those calipers, which isn't the most accurate way to measure. Also, you can or may have to alter the dimensions for your own application. This is just another way to alter ride height in the rear. And yes there is enough movement of the shock with this bushing that you may have to grind some clearance on the shock linkage arm to clear the spring.1. I.D. bore of shock body after factory bushing has been pressed out. 1.028" 1a. Width of shock body at bore. .75"---------------------------------------------------------------------------------------------------2. O.D. of eccentric bushing. .910" {1" dia. mild steel stock that was available at the time}3. Width of bushing 1.182"On this dimension, measure the actual width of the frame that the bushing will be fitting into. You want them to be as good a fit as possible, so the frame won't be crushed when you are tightening the bolt. This insures that the bushing will not rotate in use.4.Drilled hole diameter through the bushing. .390" 5. Drilled hole of bushing, offset from centerline. .200"------------------------------------------------------------------------6. Delrin bearing O.D. 1.027" {teflon impregnated Delrin}7. Bearing I.D. .911"8. Bearing width. 1.182" {See #3 above}------------------------------------------------------9.Delrin thrust washers {2} O.D. 1.2"These are to keep the shock body centered between the frame.10. Washer I.D. 1.028"11. Washer width. .21"-------------------------------I think I read somewhere that the linkage ratio on the 86 GSXR750 is something like 4:1. Which means with my .2" offset that should be about .8" at the rear axle. My rough tape rule measurement showed 1", but there may be some variability in there, and a tape rule isn't very accurate.You may be able to get a little bit more offset if you don't make a Delrin bearing like I did. Then make the bushing O.D. say 1.027". If you go that route you may want to use some manner of oil impregnated sintered bronze for the bushing material so wear of the shock body bore won't be an issue. After I made and installed the bushing {in tallest setting}, and after measuring the differences in tire diameters from the 18" rim set to the 17" set, I pretty much effectively raised the back/lowered the front so I did get an approximately 1 degree drop in front end rake from OEM 26 deg. to 25 deg. I wasn't shooting for a specific number, just wanted to make sure that the switch to 17s went well with no drawbacks.

No, but I'll dig up a post from another forum that has the dimensions and post it here.

I tried dropping the forks a 1/2" but when I had .90 fork springs in, I would drag the lowest socket head cap screw on the starter clutch side. {Track days} So I try to avoid that. With my Ohlins I did make an eccentric upper bushing that allows me an additional +or - 3/4" of ride height.

Hi fellas. New here, so bear with me as I learn the ropes. Yes I read the fucking rules. I am an original owner of an 86 G. It has a host of mods like they tend to get as the years go by. Anyhow, I would like to know the OEM spring rate for the 86 750. I have the 1100 rate as 6.1 Kg/mm {340 lb/in}. The reason I'd like to know is I am using the 1100 shock linkage on my bike with an Ohlins shock. The Ohlins is the SU 5274 shock set with the stock 1092-24 spring that comes with it. {8.15 Kg/mm 457 lbs/in} I have a sneaking suspicion that the leverage ratio of the 1100 linkage is different than the 750's linkage. With the stock linkage and the Ohlins, ride compliance is very supple. With the 1100 linkage, it is far too firm. Firm enough that when heeled over and my knee skimming the deck, it will skitter if it hits pavement ripples. It never did anything like that with the 750 linkage, and this is with Michelin Power Supersport tires mounted, scrubbed and at Michelin's recommended track day pressures. I did some minor rebound/compression damping adjustments but to no avail. My thinking is, if the 750 {a lighter bike} has a higher OEM spring rate than the 1100's OEM spring, that would confirm to me that there IS a different ratio in that linkage. The to get the 1100 linkage to work better on my bike, I'll have to go a similar spring rate as the 1100. Like many, I'm using the 1100 linkage to quicken the steering response.