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Discussion Starter · #1 ·
Figured someone might come looking for this info so i thought id post it up. Will add more in the future.

Short stroke motors came in the 1988 and 1989 gsx-r 750 motors. They were 748cc displacment instead of the long stroke 749cc motors.

Bore: 73mm
Stroke: 44.7mm
Compression: 10.9:1
Deck Height: ??
Combustion Chamber: 22cc (pretty sure 1989 is the same but not 100%)
Base gasket thickness (uncompressed):
Head gasket thickness (uncompressed):
Intake valve size:
Exhaust valve size:

*Note: Be careful when ordering a new cylinder block or a used one. There are two versions, California style and regular. Not 100% what the differences are but if i had to guess i would say the california block would be taller (less compression)

California part #
old # 11210-20C10
superseeded # 11210-17C14

Regular
old # 11210-20C00
superseeded # 11210-17C04

Camshaft specs:



Dyno run showing stock HP (not my bike)

 
G

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I think the Cali model had some kind of emission ports. I think the combustion chamber and other dimensions all the same though
 

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So, could I stick my 89' 750 motor in my 91' 750 ? Everything will match up i.e. electrical mostly, CDI, Coils, etc. Sorry for the left turn off topic.
 
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gvitup said:
So, could I stick my 89' 750 motor in my 91' 750 ? Everything will match up i.e. electrical mostly, CDI, Coils, etc. Sorry for the left turn off topic.
I would not use the ECU. It is programmed to a short stroke the 91 is longstroke not sure of the redline on 90-92 750's but the early ones lined lower than the short stroke and I think the ignition curve will be a bit different between the two motors. If I was going to mix and match I would use 86,87,90,91,92 and keep wire looms and ecu's of the 88-89 by themself.
But yes I bet you could you may not have the optimal ignition curve and rev limiter will kick in early but you could run it I bet.

Oldskooler,
I was thinking of the oval ports on the Juggs:duh.

They are on the cylinders not the head. Cali head may be different I bet Long_Av8r would know
 

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Oldskooler,
I was thinking of the oval ports on the Juggs:duh.
Isn't that what he is talking about??? If so then yeah, the Ca model had some oval ports on the block though they can be blocked off. If you look at the 49 state block you can see where the ports are cast but not machined just under the exhaust ports on the head if it were bolted together.

The heads are the same.

ECU's don't swap between long and short stroke because the curves are different.

ECU's do swap between long stroke but require some wire harness mods, but even if you do mod the harness its not a good idea to do since the redline is different on the later generations. My 1127 ECU is wired into my 87 750 harness - which is now made more like an 86 750 harness. It required plenty of splicing and study of schematics. I hate to admit to it, but it took me an entire day to do, but I also tore apart the whole harness and retaped/rerouted it so that it looks factory.
 

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Discussion Starter · #7 ·
Yeah im talking about the cylinder BLOCK not cylinder head. I dont even know if block is the right term but ah well. I know what ports youre talking about now, what purpose do they serve?

I think the 91 750 had a 13K redline just like the 88-89's didnt it? Im sure the curve is different but i had thought the redlines were the same.

Brian dont worry about threadjacking, i could care less
 
G

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[quote name='Old Skool_R']Yeah im talking about the cylinder BLOCK not cylinder head. I dont even know if block is the right term but ah well. I know what ports youre talking about now, what purpose do they serve?

California Emissions I am quite sure.
 

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Holy crap, I thought this place dissappered. I'm back, let the tread jacking begin.

Seriously though, good info Rob. Thanks
 
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1+ good stuff. You need someone to come through and delete all our junk so the important stuff isn't buried in the woodpile.

Nice work as usual
 

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Discussion Starter · #11 ·
thanks for the kind words guys. I know how frustrated i get when i cant find info, so i try to post it up so people dont have to pull their hair out like i did. Will have more info coming, just been lazy.
 

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Those "ports" are for a "PAIR" valve. Yes, it's just an emisions thing. They sell block off plates w/ gaskets for 20 bux on fleabay. Almost all the newer gsxr's have them. And the B-12 motors do too. You just block 'em off.
 
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