GR650 top end on GS450 bottom end?

[scottychop]

Why not just source some actual GR pistons? Then the compression issue would be a non-issue? The combustion chamber looks to be the same for both heads.

[GregT]

Who was it said "impossible to find GR pistons" a few posts back ?

Agreed if you can source them by all means use them.

Going by the posted photos the chambers are quite different shapes - the ideal would be to CC them both which will tell you if the finished CR will be usable.

[scottychop]

Nice. They come up used occasionally, never new. Got me there.

[scottychop]

Just finished a long search on here about putting a GS500 motor in our frames. GregT mentioned the exhaust clearance issue and his solution was genius. Instead of messing with different frankenbike parts and tolerances, just use the whole GS500 motor, and torch the downtubes to match the new exhaust clearances, then brace. I like this idea SO much more than mix and match. Plus, GS500 motors are everywhere, and reliable. What say you?

[GregT]

It wouldn't be a problem for me as I build frames on a (semi) commercial basis....but others would need access to good welding and fabrication skills.

Personally, I think it's 50/50 as to whether spreading the downtubes or converting to a single downtube is the best solution...personal choice here as either can be made stiff enough.

[scottychop]

I too have built a few frames in my day. I think that most of the neck gusset is held together by the top three tubes anyway. The down tubes could take a nice hour glass shape, or a single downtube with a hefty wall thickness would be slick. That's like $15 worth of steel? Economic too.

[olddaddy]

I considered using the 500 engine and modifying the frame. I'm a certified welder and have done metal fab for over 30 years, so easy for me. What I would prefer, is to turn my little 450 into a 650. I was really hoping to put the GR650 barrels, pistons, carbs, and head onto my 450 lower end. If anyone knows the possibilities for that conversion I'd be interested.

[hillsy]

I considered using the 500 engine and modifying the frame. I'm a certified welder and have done metal fab for over 30 years, so easy for me. What I would prefer, is to turn my little 450 into a 650. I was really hoping to put the GR650 barrels, pistons, carbs, and head onto my 450 lower end. If anyone knows the possibilities for that conversion I'd be interested.

I just did a bit of "digging" over here: http://www.suzukicycles.org/index.html

And after looking at some scanned brochures for GR650 and GS450, I found the stroke is different between the two (GR650 is 77mm bore x 70mm stroke, GS450 is 71mm bore x 56.6mm stroke).

So, if you transplanted a GR top end onto a 450 bottom, you would have 77mm bore x 56.6mm stroke.....which is around 530cc (I think...).

Which is bigger of course, but it would be better to transplant the whole GR motor and get the full 650cc?? Assuming it fits in the 450 frame (height wise....)

[scottychop]

Yup. A transplant would be easier than any mods, but what about fun factor?

Anyone know the wrist pin size on the 450? I'm curious if we could come up with a piston in the 76-79mm range with compatible wrist pins?

[GregT]

Yup. A transplant would be easier than any mods, but what about fun factor?

Anyone know the wrist pin size on the 450? I'm curious if we could come up with a piston in the 76-79mm range with compatible wrist pins?

18mm....and i have to say it's an awkward size....I believe the 883HD which std is around 76 uses 3/4in pins as does the 750 Triumph which again is 76mm std. It's always easier to enlarge piston pin holes than find enough material in the rod eye to enlarge that.
2 valve/cylinder japanese pistons in this size are rare.

[scottychop]

Do the GS500 twins differ in pin size? The guys over on that forum are hopping up their motors with Wiseco pistons, but I don't remember if their pins are a different size?

I did a cross reference on the 18mm size and it looks like not too many bikes used the same exact pin. I guess length could be shortened up if need be though and I don't know how to check for that on babbits.

How about the GPZ1100, KZ1100, ZX1100? [edit] Looks like Wiseco changed the dome profile on these pistons and they no longer fit without some serious machining of both piston and head. The GStwins guys are having a hell of a time. If you could find some used ones... but again they are rare like the GR pistons.

Why not just go with the GS500 stockers and use the GR head?

[GregT]

The GS500 uses the same size pin as the 450 and the pistons will fit the 450 when the barrel is bored to suit.

Wisecos are probably the easiest option.

Pin length is not a problem - piston sets come with the correct length pins.

[scottychop]

Finally found the youtube of the 527...

http://www.youtube.com/watch?v=tQEVHd1cSyw&feature=related

[Charlie G]

Thanks for the efforts Scotty.

cg

[BIGYAM]

Hi, sorry to trouble you, but reading your posts it seems that you know alot about fitting the 500 engine into the 450(1980) frame, can you tell me if this is possible without having to chop the frame ?
Reason is iv'e just completed my project gs450 and the top end siezed due to oil pump failing, so need new motor, so i thought to fit a 500 but im informed that the header or exhaust pipes foul on the frame , and dont want to alter frame as iv'e just had it powder coated, many thanks Nige.