750 L questions

[Portaz13]

Just picked up this old girl,  with heaps of spare parts inc dot head and cosworth pistons, Yoshi valves , short stroke block etc  .  Anyway it was ex race bike and now has low comp on 2 cylinders (according to old owner)  it will run with choke on which seems strange if internally damaged,  owner said he was riding it made a noise and now it's like this.  Planing to pull head off and have a look but clearly head is not stock, he said possibly it had a bandit head is that possible?  Anyway I'm in two minds as to weather to go big bore setup or repair as is.  Before the mishap it made 128hp on the dyno, what would be expected power from big bore setup? 

[Fazz711]

Hi bud. Welcome. Nice project. 

[wraith]

Welcome to OSS.

The running problem sounds more like carbs/fuel to me.

I know you can put the 749cc barrels on a b6 but I would think a b6 head on the gsxr750 would not be the best set up.

Edited July 27, 2017 by wraith

[canamant]

Combustion chamber might be a bit small and it probably won't breathe very well.  750s are  bit of a pain with rgard to parts swapping.  cylinders, ;istons. heads, cranks. rods and cases cant be swapped between long and short strokes.  Clutches and input gear shafts can't be swapped between slabbies and JKLM slingshots although they can be modified to fi.  Some of the spares you have you would have to get  a short stroke engine to use.

 

[Portaz13]

apparently previous owner had planned to use short stroke block with spacer, dot head with the current flatslide setup, 1100 headers, was going to use cosworth pistons after honing long stroke rods to 19mm to suit, does that sound correct?

[canamant]

Yes, but I'd be cautious about boring out the rods.  If he was talking about fitting the 73mm barrels and head with a spacer plate I'd be on the lookout for a suitable piston to fit the standard rod.

[wraith]

Sounds like a lot of work for something you can have a lot of problems with, the gsxr1100 down pips apart from being longer than the 750 have the same bore (I believe). If you want the power, sell the 750 motor and bits, keep the DOT head and get a gsxr1127 motor or b12 put the DOT head on that, cash better spent and more fun and much more potential. 

[Captain Chaos]

What he says ^^^

Elevenize the thing.

[Portaz13]

I need to keep the engine as its matching numbers,  the bike came with all the parts needed expect spacer plate,  however I'm kinda thinking it had 128hp when running and I'm guessing Max of 140 with big bore,  seems like a lot of work for small gain.  Then again I have $1400 coswortg pistons there doing nothing,  where would I go to sell these parts?  

[Fazz711]

Get to 50 posts and the for sale and wanted sections open on here 

[Swiss Toni]

1 hour ago, Portaz13 said:

I need to keep the engine as its matching numbers. 

Change the motor out to 1127 or 12. Have your fun out of it, the re-fit the 750 motor when (if) you sell it. 

[Fazz711]

5 hours ago, Swiss Toni said:

Change the motor out to 1127 or 12. Have your fun out of it, the re-fit the 750 motor when (if) you sell it. 

Now that sounds like a good plan 

[Captain Chaos]

selling a Slingy is never a good plan

[Portaz13]

Apparently in nsw putting an 1100 in can be picked up by rms if changing numbers on rego papers,  I think i will see what's up with this engine and go from there,  haven't even researched the 7/11's yet lol 

[george 1100]

I saw that for sale and was tempted. Have one exactly the same that I restored and fitted an 1100 to. If you're not too fussed about hp keep the 750 but if you want more, don't waste your time, just fit an 1100. It has some go fast goodies there already that you could use on the 1100 also

[Portaz13]

Yes good advice I think,  depends how it goes but it does have quite a few mods already such as cams, head work,  carbs,  coils and ignition stuff so should go OK,  I hoping it's pretty grumpy 

[Dazzler]

Saw it too, he'd been trying to sell it for $4,500+ a few months ago. You must have jumped on it pretty quick, ad disappeared within a couple of days. Good score

[Portaz13]

Thanks mate,  I missed it being advertised before though which is odd but yeah pretty happy so far 

[cregnybaa]

Over bored 750s will never make the power of  a 1100, if you want to fit a 1100 engine just blitz your 750 engine and build the 1100 engine into the 750 cases problem with the  numbers solved.

[Portaz13]

Any links as to how that's done?  

[Antman]

Saw it also, where in NSW are ya?

[cregnybaa]

Just new bearings to suit the crank 1100 cylinder studs and open up the crankcases slightly to allow the cylinders to go down and shave a little off top case for the primary gear, its a piece of piss really.

[dupersunc]

only 1052 cranks fit in the 750 cases don't they?

[cregnybaa]

No 1052/1127 will both go in.

[Rene EFE]

I actually think a (bigbore) 750 is more fun