gsxr1127 crank into gsx750f will it fit?

[Almiester3]

Hi, my gsx750f shit a rod bearing. now being in whoop whoop in australia i would have to send away for machining but someone a 2hr drive away has a gsxr1127 crank. Has anyone fitted one in a gsx750f before? thanks

[Gixer1460]

Pretty sure the answer is No! Or at least not without a lot of machining and maybe welding.

[Duckndive]

You can build a 990cc ish motor using a 1100 crank apparently but wont be a 5 min job 

But as a direct replacement for a 750 crank NOOOO

[dupersunc]

1127 mains are bigger than 750 mains. So no.

[Almiester3]

thanks all, sending it away it is then 

[Turbo-mutt]

Yes you can. you need to have a 1988 750 cases and transmission 1986 crankshaft Cylinders and Head.  its been a while so i forgot the year of clutch basket.  i believe you might have to grind a little so crankshaft clears the cases perfectly.  Im fixing to change the timing chain soon so if anyone is interested I will post pictures. 

[DAZ]

Pictures are always good  and information is always appreciated and as stuff becomes harder to find in good condition the ability to swap and interchange stuff is much needed 

[clivegto]

Not done it myself but always fancied building one. As said 1052cc crank will go in the 750k cases. It's all in the frankingsteen thread in the Vault. 

Edited October 29 by clivegto

[Gixer1460]

But as the OP was talking about sourcing a 1127 crank, the above doesn't help them!

And given time, tools, ingenuity and sheer bloody mindedness - anything can be made to fit most anything else!

[clivegto]

8 hours ago, Gixer1460 said:

But as the OP was talking about sourcing a 1127 crank, the above doesn't help them!

And given time, tools, ingenuity and sheer bloody mindedness - anything can be made to fit most anything else!

Yea I know. 

[Turbo-mutt]

sorry i shoul have asked you if crankshaft bearing radius is the same then yes but you need the comlete rods, pistons and Cylinders. it will not replace  crankshaft only.  the 1127 crank drive gear willl have different teeth so then you wil have to replace clutch basket and then input shaft.  there is alot of different sizes of internal parts so try to get the correct replacement.  The guy that taught me about this was from Australia. 

[Turbo-mutt]

22 hours ago, clivegto said:

Not done it myself but always fancied building one. As said 1052cc crank will go in the 750k cases. It's all in the frankingsteen thread in the Vault. 

I want to thank you for mentioning the Frankenstein  thread in the Vault. It is exactly the information he needs and it explains why I had clutch basket issues when I did my motor. Again many thanks. 

[IhmeJanneFIN]

Having done the mk1 750F (748cc) to a running 988cc Frankenstein with the 748 cylinders and 1127F crank, so I can share some info. Would it be usefull, it's up to you to decide.

1052 fill fit straight on (no modification needed), as is stated on the Frankenstein build and I believe the 748 and 1052 cases are the same? (correct me I am wrong!)

1127F/R (and I believe also 1157 cos "same" (timing gear different)) crank can be fitted to the 748 casings, BUT, the conrod #3 will hit the oil line running from the main gallery to the transmission bearing. This can me "dremeled" down to allow the crank to spin.

BE CAREFULL THOUGH, you may go all the way to the oil line (ask me how I know, but copper brakeline fitted perfectly inside to fix the leak from the hole).

Thats pretty much for the crank that is needed if my memory serves me right. The upstairs is the more complicated part.

As the 748 casing is a bit smaller than 1127/1157, those bigger cylinderblocks don't go straight on and would need enlarging the cases (have been done by others). I believe 1052 would go straight on as 748 and 1052 use the same base gasket.

Clutch must be matched to the crank:

1052 must use 1052 basket as the stroke is 58 mm.

1127/1157 must use basket intended for those cranks as 59 mm stroke.

Stroke of 58 mm vs 59 mm clutch baskets have different amount of teeth.

Lets not forget that 1127F uses helical cut gear at the crank, so only 1127F basket fits that. (And I believe also 1127G uses helical cut gears, but havent had one on my own hands, so cannot confirm.)

1157 must use 1157 timing gears, because of the hyvo chain.

Basically this is one way, you could get 1052/1127/1157 with a 6-speed box.

If I got something wrong, please correct me, so I can edit the possible wrong info away.