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IMO boring an engine is a bad idea... first, you minimizing the chance off being able to save the engine if something bad happens to the bottom end.  second, you're not going to gain much from boring such a small 2 cylinder engine, you would be better off with a good amount of head work. third, boring out an engine is something them folks from down south do to thier chevy 350s, and this ain't no chevy 350.  fourth, you're screwing with the bore/stroke ratio and the engine was designed with the stock ratio for a reason. fifth and most importantly, there are 2 replacements for displacement: higher rpm and forced induction

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I wouldn't bore it the most you would gain on Stock Suzuki Pistons would only be 1mm per cylinder which would roughly work out to 13.247 CC which wouldn't make anywhere near 20HP.I don't think you would see any Difference at all.

It's not worth the expense as a performance upgrade unless you're actively competing in a 500cc race series.  Selling the GS and putting the money toward a faster bike is a better way to go.

-M

If you search, there is lots of info around. Many people have bored out the GS. I have probably one of the last remaining sets of 79mm wisco pistons. These have been used to bore the GS to 555cc. you can still get 78mm witch works out to about 546cc or something. Boring it out can have many advantages. I'm no expert but it will allow you to run higher lift cams. I was planning on building a GS555R with high lift cams, necked valves, ignition advancer, and all of the other goodies, but the way things are turning out it looks like I might be selling the GS before I ever get a chance. If that's the case, my 79mm pistons and rings will be for sale, but I'm going to want a decent price because I know how rare they are.

In generall, boring am air cooled motor is very risky.

A certain amount of metal is needed for thermal stability.

man if thats the way you want to go its a good option . its about they only thing you can do to get a good amount of power out of the bike . slaping a filter ,exaust on it an advancer  is only going to get you so far . you have to do motor work . i'd start out with a small bore   ( have it ported and poslished to while they have it ) cuz you dont want to do to much . yes these motors my be bullitprof but rember this. the more power it makes the more  breaks its gonna have . look around on here . find out what it is that your gonna have to do . most motor work you do its not just a simple bore / port and polish  theres normaly more motor work that needs to be done to handle it . its not a cheap  way to go but its the best way IMO  i plan on doing it

Quote from: TadMC on May 07, 2006, 08:27:42 PM
I was wondering if you guys had any advice on boring out the gsf.

1: can it be done....safely?

2: what would the recomended bore be?

M: How much does it usually cost?

Vance & Hines bored out a GS500E to 555cc way back when it was new using the Wiseco pistons.  Did usual intake, exhaust, and jet stuff and worked over the head a bit.  Performance figures are included here:

http://img.photobucket.com/albums/v443/jcp8832/GS500tests.jpg

Brought the GS up to EX500 (Ninja) level performance.  Might be easier to just pick up a Ninja 500.