Heavy duty parts for short stroke 750?

[IhmeJanneFIN]

Hi all.

I am asking for some info for some beefier parts for my bike as I am in the middle of building my GSX 750 F -94 engine to better suitable for bigger boost (about 1.0 bar).

My main questions is, are there any HD aftermarket or oem parts like HD studs, conrods or pistons (more of these later on, I want to know your opinion on my idea) that fit the short stroke engine with no or little mods. I don't want to throw thousands and thousands of euros to engine workshops for minor effects on this project.

I know the 1127 or B12 conrods don't fit because of the difference with big and small end holes (btw. short block 750 wristpin is 19mm, not 20mm) and because of the stroke is different also.

I know the engine is not the best platform to start with as 1127 and B12 are bigger cc engines and better suited for boosting as the aftermarket parts are easily available, but this is what I have and this is how I plan to roll to with my faired sleeperbuild.

I have already rode the bike for about 5000 km as boosted with mild pressure (max of 0,65bar and 174hp at the crank) as I don't have an intercooler (I am in the middle of installing my diy water methanol kit though). Now I have disassembled the top end of my engine as I am planning to install a diy spacer under the cylinder block and in the process I noticed small cracks on two of my pistons. On #1 I have a crack between my top and bottom ring on the intake side. This crack goes all the way to the bottom of the ring crooves and contiues hidden there as part of the piston between rings can move a little up and down and I can feel a small high spot on the crack with my nail. On #3 I have a small crack on the top of the top ring and intake valve crevis, which at the moment is only at the surface as the crack cannot be seen at the ring groove. On top of the pistons I can't see any marks of detonation, so this might just be failure of the material?

So my initial plan was to just get two replacement oem pistons, but o boy they are a bugger to find "cheaply" and have always wondered if there would be any better and stronger ones out there.

As I digged around the Eblag and partzilla part numbers I came across DR250/Burgman 250 pistons. They are 73mm bore and 19mm wrist pins and the different heights of this piston is identical to the 750 short stroke oem piston. Only difference that I can see from the pics is that the DR uses flat top pistons and the 750 have crown on them, so the CR would be significally lower and squish would go to hell. The amount how much lower the CR would be ks unknown at the moment. But  have ordered one of these DR pistons

edit: fleabay link removed

to measure if it would be suitable to be run in my engine. Ad states that these are forced pistons (chinese pistons so you can never say for sure) so they should be stronger, right? As far as I have googled the valves are about the same size in both engines but the angle is also unknown, so there might be issues with piston to valve clearance. I know that the CR would drop significally with these pistons but my question is how low I could drop the CR to still have a rideable streetbike? Also the squish would suffer greatly.

As stock this 750 engine have 10.9:1 CR (after 7k rpm though because of valve timing) and on the bigger oilboilers people seem to run as low as 8.5:1 CR when build for boost. These engines are a lot bigger cc though, so the off-boost torque don't suffer that much than it would on a 750 engine. As the engine was unopened on my bike last summer, the bike would start to boost around 4k rpm and at around 6k it would already have near the max boost and a wonderfull screamer soundtrack. (Fyi, turbo is from a 2.0 cdi diesel mercedes, non-vnt). So if I can keep the low rpm turbo spool on my engine that shouldn't effect the rideability too much in my opinion, but that might be wishfull thinking.

 

Ps. Sorry for long post, so here is a link to my bike on youtube making tsu tsu sounds

edit: youtube video link removed

 

 

Edited April 12, 2021 by IhmeJanneFIN
rules forbid these kind of links

[Gixer1460]

Other than you having already had the engine - why use the short stroke engine when a long stroke is better suited for forced induction - and easier / cheaper to get hold of!

Regarding the problems, please don't piss around using std cast pistons with boost - they all fail eventually! Forged pistons cost but bring reliability especially with increasing boost.

[IhmeJanneFIN]

6 hours ago, Gixer1460 said:

Other than you having already had the engine - why use the short stroke engine when a long stroke is better suited for forced induction - and easier / cheaper to get hold of!

Regarding the problems, please don't piss around using std cast pistons with boost - they all fail eventually! Forged pistons cost but bring reliability especially with increasing boost.

Thanks, but as stated, this is the engine I have and plan to use for this project for reasons of my own (stupid? maybe? crazy? definately.) so any info for this is still needed if any is to be found at all... I can live with that info also that nothing is to be found. At the moment I only would want to break the 200hp barrier at the crank (my engine dynoed 174hp at the crank last summer), so no need to go further with this build. Maybe my next project after a few other projects in few years will be a B12 turbo or some GSXR with a charger with better aftermarket support.

I know the engine is not the best canditate for more power as stated in my first post. But there are still a lot of people around the world running these short stroke 750 engines (mostly NA i would presume) for some crazy reasons of their own, so can we please, try to gather info of this specific short stroke engine here or show a thread where this info is, rather that tell of the bats "get a bigger engine"?

As far as I know there are this engine specific forced 73mm pistons to be found, but they seem to be higher CR versions only.

So far haven't found any beefier rods that use the same size bearings as stock crank.

1052 crank would fit the cases, but would require much more extra bits and work also.

Cams from few different engines fit. More of those in Frankenstain guide.

[Gixer1460]

High CR pistons aren't totally off the board - I used 12.5:1 Wiseco's in a 1186 T2'd with 10psi of boost and 35-40 deg of timing whilst using a 2mm decomp plate that took CR down to around 8.5:1 - so thats an option. Using a 1052 crank would be a good option due to the stroke increase - the short stroke 750 is and was designed to be a revvy little bastard with little torque - complete opposite of what a turbo wants to be, they are torque monsters so stroking helps. 

Remember with a will and enough machine tools ANYthing can be made to fit - odd size wrist pins - bore pistons & rods to 20mm or sleeve to 18mm - allows alternatives? Weld and offset grind a SS 750 crank to increase stroke? Stay with base stock cams unless you can afford fresh billet ground turbo cams - short duration better than long with increased lift! 

Not knowing the whole installation, you could may be achieve the target @ 10psi boost up from 7 ? Could be as simple as reducing intake temps with a decent intercooler BTW i'm not a fan of water injection - cure the detonation problem, don't use water to suppress it ! The old TurboBike magazine had a 750 F project with same goal as you but the mag died before the results were published but specs weren't a lot different to yours! They also featured a GPZ750 T making in excess of 200hp so it can be done although that used 72mm pistons and air 2 air intercooling but EFI. So looking for stock solutions to a very un-stock build, whilst economical now aren't necessarily the cheapest long term. Have fun regardless!

[Hanma-shin]

10 hours ago, IhmeJanneFIN said:

 so can we please, try to gather info of this specific short stroke engine here or show a thread where this info is, rather that tell of the bats "get a bigger engine"?

 

Ask not what OSS can do for you but what you can do for OSS.

[IhmeJanneFIN]

1 hour ago, Hanma-shin said:

Ask not what OSS can do for you but what you can do for OSS.

Well, when I get my hands to that piston and do my measurements I can provide some info then. But before that I fear I have not much to provide atm

[IhmeJanneFIN]

7 hours ago, Gixer1460 said:

High CR pistons aren't totally off the board - I used 12.5:1 Wiseco's in a 1186 T2'd with 10psi of boost and 35-40 deg of timing whilst using a 2mm decomp plate that took CR down to around 8.5:1 - so thats an option. Using a 1052 crank would be a good option due to the stroke increase - the short stroke 750 is and was designed to be a revvy little bastard with little torque - complete opposite of what a turbo wants to be, they are torque monsters so stroking helps. 

Remember with a will and enough machine tools ANYthing can be made to fit - odd size wrist pins - bore pistons & rods to 20mm or sleeve to 18mm - allows alternatives? Weld and offset grind a SS 750 crank to increase stroke? Stay with base stock cams unless you can afford fresh billet ground turbo cams - short duration better than long with increased lift! 

Not knowing the whole installation, you could may be achieve the target @ 10psi boost up from 7 ? Could be as simple as reducing intake temps with a decent intercooler BTW i'm not a fan of water injection - cure the detonation problem, don't use water to suppress it ! The old TurboBike magazine had a 750 F project with same goal as you but the mag died before the results were published but specs weren't a lot different to yours! They also featured a GPZ750 T making in excess of 200hp so it can be done although that used 72mm pistons and air 2 air intercooling but EFI. So looking for stock solutions to a very un-stock build, whilst economical now aren't necessarily the cheapest long term. Have fun regardless!

Thanks. Fun is the exact thing I plan to do with this project.

Good thinking about the pistons.

I would have wanted to run an intercooler as it would so much easiers than to fill up with "boost juice" time to time, but the space at front of F is very limited. And I don't have equipment or skills to do alu welding for an intercooler. Even my turbo is at about an 45 degree from transverse to allow clearance for front wheel and my air cleaner is poking a little bit past my righthand front fairing. Looking at pictures of B12 turbos I would say i have about half the space between engine and front wheel, as my exhaust runners are basically nonexistance as I run a log style manifold.

Basically what this bike is, it's a learning platform. It's my first ever turbo build so my plan is to do things "cheap" and somewhat differently at some things and check what works and what doesn't. Take notes and try to replicate the good ideas and toss away the bad ideas for the next boostproject in a few years.

Btw, about my setup. The turbo I am using is a GT20 from a 2.2 liter CDI diesel merc (3 bolt pattern). At the merc it is cabable to do a little above 200hp, so my hope is it would do the same on my build. As this GT20 is from a diesel engine, it has a bit smaller exhaust housing as it's petrol variant, it likes to start building boost at quite low rpm. Also because of that I haven't found a specsheet for this turbo. This turbo is a non-VNT variant. Would like to try out a VNT for the kicks of it at some point. The turbo cost me 50€ so what the hell, I just slapped it in there as a try to find out if would even boost before redline. I was quite pleased to find out it boosted quite early actually and still revs to redline quite easily.

Because I didn't have any intercooling last summer, the torque started to die at higher rpm quite quickly, so my high intake temps might have been the cause. On my katriders site the dyno sheet can be seen and other bits of my mods.

https://katriders.com/forum/service-department/exhaust-mod-shop/2120086-yet-another-turbo-build-but-bike-is-actually-running-already

I am also still running stock ignition with +4 degree timing by turning the base plate of my ignition (yeah i know, crazy) but it still works even at redline with JR9B plug gapped smaller. With original gap it started to misfire near redline. Some point I wish to update to atleast dyna coils or even to full programmable ignition (Speeduino maybe, Dyna 2000 is quite expensive for my taste).

Fueling is still done by original 36mm carbs with a bit smaller main and pilot jets actually. Malpassi 1:1 fuel regulator with about 2-3 psi base fuel pressure. I also have factory pro needles at the moment on, cause it works best with those on off-boost situations. If I floor it before boost it goes too rich at around AFR 9, but once it starts boosting the AFR goes to around 11,5-12 and stays near that to redline. With oem needles it was jerky on off-boost situations and I rarely floor it so the AFR stays quite nicely around 12 at low throttle openings at off boost situations. Might try some stiffer springs at the carbs to slow down the slides with the factory pro needles as I think they rise too fast which then causes richness (or I am thinking this wrong)?

Cams and timing are original, but plan is to make adjustable gears and try the 110/110 timing.

Exhaust what I had last summer was a single Viper can on the right side. Now I have updated to 2 cans purely just for the looks. Exhaust was and still is 2,5" from turbo to can(s). Can outlets are around 55mm. Boost was originally controlled with the internal wastegate but that proved to be insufficient so moved to turbosmart style external wastegate with screamerpipe.

Maybe I should make a new thread of my build, and try to keep this topic focused to the actual engine (addes some pics of my bike)

 

Edited April 12, 2021 by IhmeJanneFIN
writing errors

[Hanma-shin]

It’s not a katana, RTFR 

[Gixer1460]

29 minutes ago, Hanma-shin said:

It’s not a katana, RTFR 

Hey - back off! Don't quote rules that don't apply!

Apart from a reference on a youtube title I see no mention of the word Katana to describe this bike on this site!

[IhmeJanneFIN]

1 hour ago, Hanma-shin said:

It’s not a katana, RTFR 

Uuuuhmn, I haven't said that word on this site, have I?  I myself know it only as GSX 750 F, as that is what reads on the fairings and I have spoken about this bike as an F, right?  And I put that "name which should never be pronounced here in this site"  in parentheses to the youtube video name only as clickbait for my the fellow bikerfriends on the other side of the big pond also known as Atlantic ocean  okay, maybe i should't have posted the video and fleabay link in the first place as for the sacred rules, so why I decided to remove the links so you wouldn't loose your good night sleep because of me 

Edited April 12, 2021 by IhmeJanneFIN
typo

[Hanma-shin]

Blah blah blah de blah....just saying.

[dupersunc]

Fuck me, @Hanma-shinhas heavy hands this evening.

[mikeyd]

Very clean build, I like the turbo placement and keeping it within the fairings. 

[Hanma-shin]

Sleeper for sure

[IhmeJanneFIN]

7 hours ago, mikeyd said:

Very clean build, I like the turbo placement and keeping it within the fairings. 

It has been one of my stupid goals with this to keep the oem looks, so bike looks as ugly as it is with them, expect the back end is swapped from a 600 purely for "better" looks.

 

6 hours ago, Hanma-shin said:

Sleeper for sure

Then I would consider the looks a success. Thanks.

[IhmeJanneFIN]

Been thinking the pistons for my project as I found signs of starting failures on my oe cast pistons. I noticed that k1 k2 gsxr 1000 has 73mm and from looking at pictures they seem to be forged pistons, but 16mm wrist pins. So my thought was next: can i bush the oem conrods 19mm small ends to 16mm using properly sized bushes (obviosly at engine shop)? I have no idea if the pistons height and any other dimensions would work for the short block engine to make decent compression for turbo and not hit the valves. Anybody has any info on this?

[Jmckechnie]

@IhmeJanneFIN

glad to see another 750 turbo project on the go! There aren’t as many out there as the other bigger bikes. I’ll be following ya on this one. I’ve done a 750 turbo myself, but I used a 750L as my mule. I don’t know much about the short stroke 750’s, but there seems to be a lot out on the road still! In Canada at least..
 

I’ll be starting my second turbo bike project shortly- my platform will be a GSXf600. Target HP will be around 200. After discovering all the similarities the 600’s have with the long stroke 750’s, I can’t wait to see how the end result will work out! I have several longstroke 750 motors , and recently picked up 2 mostly complete gsx600F’s. I just need a place to work on them now 

[IhmeJanneFIN]

On 7/18/2021 at 8:11 PM, Jmckechnie said:

@IhmeJanneFIN

glad to see another 750 turbo project on the go! There aren’t as many out there as the other bigger bikes. I’ll be following ya on this one. I’ve done a 750 turbo myself, but I used a 750L as my mule. I don’t know much about the short stroke 750’s, but there seems to be a lot out on the road still! In Canada at least..
 

I’ll be starting my second turbo bike project shortly- my platform will be a GSXf600. Target HP will be around 200. After discovering all the similarities the 600’s have with the long stroke 750’s, I can’t wait to see how the end result will work out! I have several longstroke 750 motors , and recently picked up 2 mostly complete gsx600F’s. I just need a place to work on them now 

Glad to hear that someone else is also mad enough to build these smaller engines.

At the moment my engine is in parts as I try to build a "stroker" engine with different crank and rods, but use the original lower end and block & bore with k2 gsxr 1000 forged pistons. So I need quite a big spacer to lift the block. And I am trying to limit the spacer height, so I ended up trying shorter conrods.

Everything on this engine build is still unsure and very experimental, so I have no idea if it would even work. Will try to post results if I get it done.

[Reinhoud]

Do it right straight away! Don't do a bit now and a bit later. If it f#cks up it's going to cost a lot more! 

Ask me how I know

[clivegto]

7 hours ago, Reinhoud said:

 

Ask me how I know

How do you know  

[Reinhoud]

20 hours ago, clivegto said:

How do you know  

 

 

 

 

[latheboy]

Late to the party but so be it.

I'm sure I read on here about the combination of the short stroke 748 mixed with the long stroke 749 created a 883cc 

Ka#$&aki pistons may have been used ( I've been mia for a while, can we say other brand names?)

I have the long stroke turboed on 10psi with -5° ignition timing by turning the plate too. 

Did you really advance your timing? There be some heat in there because of that. 

Any updates on the engine parts?

I just picked up a 748 with the grand plan of putting it in the shed for years, forgetting about it, buying something else, then find it again and doing the 883 build

 

[clivegto]

Yea I remember reading that but can't remember which Kwak pistons were used. I have engine parts in the shed that I will use some time. 1052 crank in 748 crank cases is my plan  

[slingy1157]

My short stroke build thread is on here somewhere. 
Wiseco listed the largest pistons for these engines with a rebore at 76mm. So I ended up finding ZX10 pistons. Think mine were 05 model. These are factory forged flat topped pistons but I think 17mm wrist pin. So like you stated I got the rods bronze bushed to suit that pin size. Deck height was pretty good but very slightly low. This combined with the flat top and larger valve pockets gave about an 8-1 cr. The block could be skimmed to perfect deck height and run one layer of the multy layer steel head gasket would help get it back to 8.5-1. 
being 76mm means you can run a 1052cc head gasket too which is helpful. This gives an 813cc engine with turbo friendly CR and forged pistons. Mine were $40 with the rods, combined with $150 for the rod sleeving and then a rebore, so pretty good value for money. 
I think the rods will be fine for 200hp. Studs is the problem. You can use 1052 ARP studs which are too long. But there is room in the head and around the cams to machine up very thick washers to make them work. Tip- replace the studs when your cases are apart getting the rods sleeved so when the old ones snap off in the cases it’s easier to get them fixed lol

[IhmeJanneFIN]

On 5/8/2022 at 1:28 AM, latheboy said:

Late to the party but so be it.

I'm sure I read on here about the combination of the short stroke 748 mixed with the long stroke 749 created a 883cc 

Ka#$&aki pistons may have been used ( I've been mia for a while, can we say other brand names?)

I have the long stroke turboed on 10psi with -5° ignition timing by turning the plate too. 

Did you really advance your timing? There be some heat in there because of that. 

Any updates on the engine parts?

I just picked up a 748 with the grand plan of putting it in the shed for years, forgetting about it, buying something else, then find it again and doing the 883 build

 

I retarted it about 4-5 degrees. I must have misunderstood the meaning of minus and plus on ignition timing back in the time when i wrote here.

 

Updates on the engine is, that it is currently a running testbench with a truly Frankenstain engine waiting to blow up.

Basically it is a 988cc engine, which is achieved with:

 

Stock 750f engine block (6 speed) and cylinder is stock 748 block with 12 mm spacer under cylinder. Cr about 8,5:1.

Stock 1100F crank (helical gear, but cost only pennies vs 1127 or 1052 crank)

Stock 1000 k2 gsxr pistons

Zx14r rods, shorter and a bit beefier than 1100f rods, so thinner spacer needed. Rods were machined thinner at both ends to fit crank and k2 piston. Running with 1100f bearings as there was too much clearance with even thickest oe. zx 14 bearings. (had to make new stop grooves for the bearings). Small end bushed to 20mm->16mm.

Oem 750f cams timed to about 110/110 degrees to suit turbo better.

Custom build 750f clutch as the 1100f i bought had shot discs and didn't fit under 750f right side engine cover (basically 750f clutch basket with swapped 1100f helical gear). 6 spring pressure plate with 2 heavy duty and 4 oem springs, so clutch lever is still ok to use. Hydro clutch conversion. Seems to work fine for now and holds current power levels. Hoping to achieve 200 hp at the crank, anything over that is a plus.

Still running GT20 turbo from the M-B but with new custom made manifold. Turbosmart "style" external 40mm wastegate with screamer.

Two stock 600f oil coolers, upper one for engine, lowe one for the head. Oil temps have maxed at 86°C when cruising even with outside temp at near 30°C. There simply was no room to fit aftermarket oil coolers as they are way thicker than oem suzuki ones. Plus these 600F coolers cost like few pennies vs. aftermarket oil coolers.

Plenum has two reed valves to help engine breath more freely when not on boost, as it doesn't need to suck air through the turbo and boost piping.

Stock 1100f cdi box with ~4° retard by turning base plate. (1100f cdi has lower redline than short stroke 750f). Gsxr k6 600 COP coils. Hoping to run efi someday

 

Turbo starts to boost around 3000 rpm and hits max boost around 4000-5000 rpm, so basically there is no boost lag if rpms are above that. Bike drives like an NA carburated big cc bike (like a stock B12 bandit what I drove years ago). Power comes on linear and there is no huge spike in power like there was with 750cc turbo engine. With bigger cc engine it has enough torque to cruise low speeds near idle and still accepts throttle inputs.

Gearing is 17-43, so rpm is about 4000 rpm at 110 km/h at 6. gear. There is no boost and no exhaust pressure when cruising, but if I floor it, it immediately starts to boost and basically has full desired boost in a few seconds.

Boost pressure can be set at different levels with a flick of a switch by my right thumb. I have done a relay mod to my lights, so my original light switch on the right hand is now used to control solenoid valves which control boost. Basically one basic solenoid valve and 2 stage boost controller in line.

Basically with my "lightswitch" at "no lights" setting, it is running on spring pressure of 0,6 bar. With only "park on" it can run anything between 0,6-1,2 bar. It's currently set to 0,8 bar. And with "driving lights on" it can also run anything between 0,6-1,2 bar. It's currently also set at 0,8 bar, as I want to test drive the engine a bit more and add water methanol charge cooling before upping the boost.

I have a boost gauge, exhaust back pressure gauge and wideband installed. When boosting 0,6 or 0,8 bar, the back pressure is little over 1 bar. A bit on the highside, but still quite ok and engine seems still happy and lively.

Even with 17-43 gearing, it lifts the front with ½ throttle at 1. gear when full boost hits. With the boost set at 0,8 bar, it's quite a funny feeling to accellrate as it wants to wheelie on 2. gear with about ¾ throttle and around 100km/h on the clock, so there is definately power on the engine, the reliability is the only question now, which i have to continue to test and dial the lower rpm afr's.

Currently fueling and drivebility is ok at wot and cruise above 3000 rpm, but at revs between 2000-3000 rpm, it likes to surge for some reason. I thought it to be lean surge, so I richened the mixture there with different idle jets, but that doesn't seem to be the case, because even with 12:1 afr it surges identically as with ~14:1 or ~16:1 afr. Might be the new placement of my reed valves that disturb the flow inside the plenum, so I need to try different locations and recheck my carb sync at that rpm.

But here is a pic. Turbo placement is quite unusual, but it still fits under my new fairings (in the middle of facelifting my pre F to post F, so more room came available for turbo placement and now able to drain turbo with gravity). Heat from turbo and downpipe might become an issue and might melt the plastics, but I try to deal that with heat shields, turbo blanket and exhaust wrap when the time comes to fit the fairings.

Frame is currently stock, but with post F swingarm fitted with gen 1 busa rear wheel and 190 tyre. Front end is from -03 SV1000 S which I had laying around from my other bike after gsxr front end swap. Front wheel is from srad gsxr. Still need to get it painted black at some point.

Edited August 23, 2022 by IhmeJanneFIN
Added more info, which became to be novel.