Looking for advice for tuning my gsxr 750 1990

[Jpich85]

I've been thinking a lot lately about what I could do to tune the engine and get the most out of it and improve performance in any way I can, I'm still not at that point in the build but wanted to get some ideas and see where my money would be better spend on what parts.

I know I should probably just by a 1100 engine but for some reason I want to keep the 750 and just tune it up a little with what cash I have.

I was just after some ideas as I know a lot of you guys on here have plenty of knowledge on engines which is something I'm not too familiar with.

Is a dyna 2000 kit worth the money?

Would you bore out the cylinders and increase the cc some what or wouldn't you gain much bhp? And I've seen about installing busa pistons but I'm not sure if that's just on the 1100's? Are there cams from a similar bike that would give me a small improvement?

 i found a tuning article online about putting a stage 3 kit on it? Maybe that would be a good start.

any help would be great.

cheers

 

 

 

 

 

 

 

 

 

 

Edited May 23, 2018 by Jpich85

[Nik]

I hate to rain on your parade, but I'd stay away from spending time and money on tuning the 750. Sure, big bore kit, porting, cams, carbs, exhaust would make it more powerful, but at very high cost, and relatively low performance improvement. An 1100 is the sensible option. Just my two cents ...

Edited May 23, 2018 by Nik

[Swiss Toni]

+1 ! 

[Swirl]

+2 

[Jpich85]

Thanks guys maybe that is the best option then, I guess with all the money you'd spend tuning the 750 you could buy a 1100,

would it be a straight swap changing to an 1100 engine?

I think an 1100 would he plenty for me so I dout is tune it much.

Are the dyna 2000 kits worth the money?

thanks for your help everyone

 

 

 

 

[dupersunc]

dyna 2000 are a complete waste of money.

Wiseco do big bore high comp piston, a nice exhaust, and properly set -up carburation, would give you similar power to a stock 1100 and keep the revvy nature of the 750.

A quick way to spend a grand.

Edited May 23, 2018 by dupersunc

[Jpich85]

Thanks again, I've had a quick look for a 1100 engine but on Eblag there isn't much about, would the 1100 be a simple swap of the engine or do you need the cdi and wiring loom?

there's plenty of bandit engines tho, are the bandit 1200 engines a good swap?

[MeanBean49]

Bandit engines are a good swap. Easy to do and you can use the gsxr carbs and cdi (just be wary rev limit is a bit higher, if motor is good and your not doing constant limiter bashing its not an issue)

Depends what sort of motor you want. Lazy easy power or somthing you have to rev and work the gearbox. An 884 big bore on the 750 lump with some head work will be quicker than a stock bandit/1100 motor.

[Swirl]

What 750 motor is it, you will be able to recoup some of the cost selling that, bandit 12, or 1127 powerscreen motor the way to go I expect, mid range torque from the powerscreen would do you I expect, I sold a whole rough but running bike 6 mths ago for 500 quid 

[richyrich]

Zx10 pistons for cheap big bore . Same gudgeon pin diameter.  Someone mentioned this in turbo forum, said it made low compression, but couldnt you machine down the block or the head ? anyone experience of this like to share

[Fula28]

Hi Jpich  , if it's 750L,M 1990 they made good numbers stock, but like rest of the guys say cheaper to bang a b12 motor in and fit your 38mm carbs from 750 m. Headers  and nice set up would make 120bhp ish. You can tune of course the 750 motor but it's going to be £1000-£1250  to get that power and be a screamer not torquey like bigbore motors.

[Hellraiser6662]

Mine is a 750L ok its a rat but hell soon as you dump that airbox you are in a world of hurt, mine had its airbox take away before i got it, then because of the way a new subframe was added there was no way i could get a airbox back, so i had to deal with k&n crap filters, and flat spot city, i had somebody play with it and got it to run ok but the flat spot at 4 is a knightmare hole, and one ive got to dig out off every ride 30 mph is shit, its iver to higher gear to keep out of 4 or to lower gear to keep under it. Every thing ive read about it is dont bother tuning just added a exhaust, 4° advancer, may be better filter and thats about it. Otherwise you can join me on flat spot hell... haha 

[Jpich85]

Thanks for your advice again everyone, I rode the stock bike before I started my build and it already had that annoying flat spot even in its stock state and with the way the subframe is going it'll look better with pod filters even tho I know it'll run not so well, it also popped into neutral a few times while I took it for that first ride so I'm not sure if that would be an issue that would need addressing?

I have a rf900/750 head in my wn so I do like a more torquey ride and wasn't too keen on the revvy 750 engine.

The 1100 engines seem rare to find on Eblag so maybe a b12 would be an easier option.

Does anyone know what year bandit would be best to use in my 1990 gsxr? Would pod filters be ok on the bandit engine and would I have to re jet the carbs?

I did the jetting on the rf900 and it's ok but not perfect.

I could sell the 1990 engine and I still have remains of the 750wn rotting on the floor in the garage so I could strip that maybe and sell the parts?

thanks everyone

 

 

 

 

 

 

 

 

 

[MeanBean49]

2 minutes ago, Jpich85 said:

Thanks for your advice again everyone, I rode the stock bike before I started my build and it already had that annoying flat spot even in its stock state and with the way the subframe is going it'll look better with pod filters even tho I know it'll run not so well, it also popped into neutral a few times while I took it for that first ride so I'm not sure if that would be an issue that would need addressing?

I have a rf900/750 head in my wn so I do like a more torquey ride and wasn't too keen on the revvy 750 engine.

The 1100 engines seem rare to find on Eblag so maybe a b12 would be an easier option.

Does anyone know what year bandit would be best to use in my 1990 gsxr? Would pod filters be ok on the bandit engine and would I have to re jet the carbs?

I did the jetting on the rf900 and it's ok but not perfect.

I could sell the 1990 engine and I still have remains of the 750wn rotting on the floor in the garage so I could strip that maybe and sell the parts?

thanks everyone

 

 

 

 

 

 

 

 

 

Any model bandit 12 lump will be fine.

Pod filters will be fine, you will need to re-jet but its best to get it setup on a dyno.

Its a complete old wives tale about not getting rid of the airbox. 

Your not making the engine take in any more air than it was before. You just need to get the carbs aetup properly to compensate for the air being a bit more dense.

Never ever had an issue getting a bike to run fine even with open face carbs with no filter

[Jpich85]

Thanks mate, I'll start looking and doing some research on the b12 swap, might dry and sell a few bits and get some money up together for it,

what exhaust headers would you need? The b12 ones, I've bought the vance and hines megaphone for this project, not sure if it's the best performance wise tho.

Would i need a braced swingarm with a 1200 engine?

 

Here's a pic of it so far, excuse the pose I was just checking riding position

 

 

[Swirl]

I like that, looks sweet

[Fula28]

Looks Promising  jpich,  use 750L carbs with b12 and gsxr 1000 k headers titanium cheap light . But only k1-2-3 as there connected down tubes after that, they can be heated an moved about to suit, Loads of fun an you will never look back. You can also use 750 loom cdi ect. But just don't bother reving it over 10.5k . As b12s won't make power same as 7fiddy.You can punt 750 motor out.

Edited May 26, 2018 by Fula28

[Jpich85]

 

Thanks @Fula28
I'm trying to keep this bike quite small and compact if possible. Thanks for your help with the b12 engine. Just a few more questions if that's ok.

Would I need a bigger battery?

Would I need the starter and alternator from the b12?

What oil pain is best?

Would i use the b12 pick ups?

 

I've read a little about tuning the b12 like putting a dot head on and gsxr cams but I don't think I'll get into that yet.

 

 

 

 

 

 

 

[Fula28]

No for battery use what ya got, starter an genny from b12 best.And b12 sump depends on exhaust system you have , B12 pick ups should come with motor. Dot head been there done that long while back cheap Hp. 130-147. Depends on head and tune. Last one we did is still going strong after 8 years of hammer.

[Jpich85]

Thank mate I really appreciate your advice and am very greatful, engines aren't something I know a lot of so am keen to learn what I can from this site and people like you.

I've got a good base point to go from now. Once I weld the subframe and find some suitable lighting I'll focus on the engine then.

Thanks  @Fula28