Gs500f Big bore

[OzzyRZ]

Gday guys.
I have been trying to find if there is a bigbore piston option out there for the later gen GS500f. I cant seem to find anything.
Surely someone has done a kit or grafted a piston out of something else into a GS.
Any help is appreciated

[cbrfxr67]

Was hoping there'd be an answer,... cricket cricket crickets,..

[Bluesmudge]

I know there were bigger bore race bikes people made back when it was more popular to track the GS500s. Some Wiseco pistons do work but I don't know any of the details. You will have to search through the forum. Most of those guys don't post here anymore.

[phlogistian]

Hey, fellers,
Big bore pistons for the GS are no longer available AFAIK. Wiseco used to make a 555cc kit (79mm bore) but they haven't been available for probably 20 years. I have a pair of the Wiseco pistons & I've considered sending them to someone (Arias, maybe) to have them duplicated, but I'm sure it would be quite pricey.
Basically, your only option is to send a stock piston to a custom manufacturer (again, Arias, for example) & ask them to duplicate it except with a larger bore. Best of luck & I'd like to hear how it turns out if you try that route.

[chris900f]

The 2-valve GS1100 was a popular platform for drag bikes, you would need to check spec's for the wrist-pin etc

[chris900f]

The 2-valve GS1100 was a popular platform for drag bikes, you would need to check spec's for the wrist-pin etc

I checked Weisco and it was a bust...also, I think the wrist-pin is 20mm, anyone know for sure?

[mikeg]

not sure of accuracy, but MTC Engineering indicate theirs are 18mm for all GS1100 years.

https://www.mtceng.com/pistons/suzuki/gs1100/

[Joolstacho]

I think if you are wanting a GS500 which goes a fair bit quicker than a GS500, you need to look elsewhere... A Kwacka maybe, at least a twin with 4 valves per cylinder. You simply can't get the mixture in and out well enough as it is. Bigger valves? More cam lift and duration? Nup they'd be tangling and too heavy, you'd have a bomb. Shame, but there it is. Try an SV650?

[mr72]

@Joolstacho is right. The big hp mod long ago was to chop a GSX-1000 head down to the middle two cylinders and fit it for its 4-valve breathing. This enables the GS engine to make so much power it breaks the crank. Any other solution to get more than ~50hp out of the GS engine will result in the same fate, I'm afraid.

I guess I can kind of understand the more power folks with GS500s since my own Bonneville has way more power than it needs and I am still eyeballing that 904cc kit with hopes of getting it over 100rwhp. That's just for bragging rights, though, and to keep me from looking too hard at a Speed Twin. Still, a stock GS500 is more than adequate for street motorcycle hp. Just some other bikes are even more "more than adequate".

[Roofaloof]

If you're looking for a bit more power, you could have a machine shop skim/deck the cylinder head. This will increase the compression ratio and cause the engine to make a bit more power.

You'll need to use higher octane gas to avoid detonation.

I don't have experience with this process on the GS500, but I've done it successfully on a single cylinder engine. It's a pretty common hot rodding technique.

You'll want to find a machine shop that does this sort of thing regularly. They can help you figure out what needs to be done.

[Joolstacho]

Well you'd also need to be VERY careful regarding timing chain length and tensioning, and valve to piston clearances.

[Roofaloof]

Well you'd also need to be VERY careful regarding timing chain length and tensioning, and valve to piston clearances.

Definitely. Lots of variables to consider when doing this.

[chris900f]

Found this looking for something else. 541cc w/78mm pistons. Any of the old timers remember this guy?

https://gstwins.com/gsboard/index.php?topic=14401.0