Upgrades for 91 kat 600

[poorwboy]

Hello I have tried the search to no avail. I got a 91 600 for free but it needs new pistons. I have heard you can bore the cylinders to except 750 slugs. Is this true. Thanks in advance.

[Court93kat]

Yes, you should be able to bore the cylinders to accept 750 slugs without any issues. Where will you be getting the 750 pistons? Buying new or picking them up cheap somewhere? If you plan to bore anyway, you could always take it out 1 more millimeter and move it up to a 771. Just a thought.

[md86]

Yeah , but then you need the bigger pistons , which are like $129 a pop . 771 kit is I THINK $550 for the works . Not cheap . Maybe get you some new rings and have the shop bore it out so it all matches up . I think it's like $80 to have your cylinders bored , too .

[Court93kat]

I only mentioned it because he mentioned boring a 600 out to a 750. That is why I asked about where he is getting the pistons. If he has them laying around already.... cool, use them. If he can get some from a buddy cheaply.. cool go with it. If he is going to have to buy new ones anyway... just letting him know he can go a little bigger while he's at it. That's all.

[loudnlow7484]

The 771 kit is like $410 from dynoman.
You can find NOS pistons on ebay for the long stroke 750's for cheap sometimes.
My only concern would be your head. Well, not yours, but the one on your bike.
I think the 600's had a much smaller combustion chamber, which would raise the compression a whole bunch. I don't know how the head is layed out compared to the 750's, so I don't know about valve clearance.
You'd probably be better off either A-just replaceing with 600 pistons. I'm sure Suzuki made .5-1mm overs for it.. or B- swapping the cylinders and head from a long-stroke 750 onto it. Preferably a 90, since 91+ valvetrains got a little frail, if I've read correctly.

[poorwboy]

does this show me posting. I have replyed a couple of times and it doesnt show.

[poorwboy]

Its working now. Or should I just stay with the 600 and do some head porting. It has full yoshi ex,k&NS,jet kit.

[poorwboy]

bump. anybody outthere with suggestions

[md86]

What , for the bore thing ? Isn't there some sort of frankenmotor you can build using parts from the 600 and 750 and an overbore kit .....

[poorwboy]

^^^Ya thats what im talking about but I dont know where to start.

[Court93kat]

You can use your current 600 head and save some money by keeping it. Just have the cylinder bored and get a 91-92 GSXR 771 piston kit.

Honestly, it all depends on the amount of $$ you have to spend on it. If you are looking to keep it real cheap, you can go junkyard shopping for a donor motor. If you have some $$ you can get the GSXR 771 kit ($400-500) and get your cylinder bored out (local machine shop rate) and put it all together. Even if you go up to a 750 or 771 you can keep your 600 head without any compression issues. You CAN get some head work done if you want it to run that much better, but it's not necassary for it to run well.