Pre 600 bottom with pre 750 top

[Timt794]

Has anyone swapped a 750 topend onto a 600 bottom?
Or can someone direct me to a thread that has info on doing the swap.

[Sin]

cannot be done wrist pins are diff diameters

[Timt794]

Thanks didn't check that.

Funny I checked crank and inserts but didn't check wrist pin
So a 600 crank can go in a 750 and run a 750 top end using
the 750 con rods?

[HemiKat]

I believe the 750 and 600 heads are a direct swap. Not an expert but Im sure some on here can awnser it.

[loudnlow7484]

http://katriders.com/vb/showthread.php?t=65034

http://katriders.com/vb/showthread.php?t=64215

http://katriders.com/vb/showthread.php?t=54119

A couple of threads of when I first decided I was going to do this. 2 years later, I still haven't done it..... I've gotten all the parts to, just ran out of motivation.

Hope that helps.

[Timt794]

Thanks for the links. I'm looking into 1986-88 gsxr pistons
they have the 18 mm wrist pin boring out my cyliners and
running my kat 750 head and cams. Shouldmake around a
636. Will post when I know more. Thanks for all the info.

[loudnlow7484]

If you run 85-87 (88 was a short stroke motor, much like the pre98 kat 750) pistons/cylinders on a 600 bottom end, it will end up being a 750, not a 636. The stroke of the 600's and the 85-87 & 90-92 (US Model) GSXR750's is the same.

BTW- I don't have first hand experience with this, but I'd guess trying to bore out your 600 cylinders to accept the 750 pistons (almost 8mm you'd have to bore out!) is going to be either impossible, or entirely too much work. I don't know if the OD of the sleeves is the same.... if it is, you could just pull the sleeves and drop 750 sleeves in it, or the much easier way, if you're already hunting down old GSXR parts, would be to just use an old GSXR cylinder block.

[Timt794]

Could I run the stock 90-92 pistons with a kat pre 750 cylinder?
Have it honed for piston and rings? Have complete kat 750
with bad crank. Easier to find the 90-92 stock pistons.

[Sin]

Could I run the stock 90-92 pistons with a kat pre 750 cylinder?
Have it honed for piston and rings? Have complete kat 750
with bad crank. Easier to find the 90-92 stock pistons.

no a pre 750 kat block is 73mm bore and 90-92 pistons are 70mm

[loudnlow7484]

Could I run the stock 90-92 pistons with a kat pre 750 cylinder?
Have it honed for piston and rings? Have complete kat 750
with bad crank. Easier to find the 90-92 stock pistons.

Uh, no. 85-87 & 90-92 had 48.7mm stroke and 70mm bore, 88-89 GSXR750 & 89-97 Katana 750 had 44.8mm stroke and 73mm bore. You'd have to sleave down a pre98 kat 750 cylinder for 90-92 GSXR pistons, or 85-87 pistons.

If you are looking for something simple (no spacers, no sleaves, no boring, etc) then just slap an 85-87 or 90-92 GSXR750 cylinder, head, and pistons onto your 600 bottom end. Trying to make the pre98 750 parts work on there is not so simple.

If you are hip to buying kind pricey stuff to make it work, you could source a set of aftermarket pistons for a 90-92 GSXR750 in 73mm and use them, but you'd still have to get a spacer to put under your cylinder block, to keep the pistons from crashing into the head. Actually, maybe it would be better to try to find some in 74 or 75mm, so you could have the kat block bores cleaned up before you go throwing a set of $400 pistons in there. I don't know how the domes would match up with the head, though. The valve reliefs might be in the wrong spot.

If you PM a member named Suzukiray on here, I know he told me he could have a custom set of pistons made up for the application. It won't be cheap, but it would be much simpler.

[Timt794]

Thanks will pm him for price and other ideas. Trying to not
have to buy an unknown motor bit seems price wise may
be the way to go.

[loudnlow7484]

If you choose to go the 85-87 top end direction, this would be a start........ http://cgi.ebay.com/ebaymotors/SUZUK...Q5fAccessories

[Timt794]

Thanks for all the help. I've decided to put a crank in the
750 eng. Now new questions what's the difernce in the
600 vs 750 cdi. What jetting to use withthe smaller carbs on
the 750? Never ending but that's what makes all of this fun
thanks to everyone for there help. Hope I can return the favor
sometime

[loudnlow7484]

the rev limit is lower on the 600. I don't know about the ignition curve, though. I've had a 600 running on a 750 box before.... Didn't notice anything different except that it would overrev.

[Timt794]

Thanks figured it should work but good to hear from someone
who's already trie it.