I'm trying to improve the performance of my track bike without making it a time bomb. Has anyone here done head porting, cylinder +1 or 2 over bore, and/or had the carbs bored? Do you have pre and post dyno numbers showing the gains?

The bike has already been put on a serious diet and a lot of chassis upgrades, but only has a slip-on + K&N lunch box at the moment... it needs more power. I wanna bridge the performance gap between the EX's and the GS without spending a fortune. Any info is greatly appreciated.

have you considered maybe dropping a tooth on front gear, gives more low end torque, ( more responsiveness off the line/curves at the expense of maybe +500rpm at full speed.  maybe consider this before you dig into the engine.
Aaron

from posters in the past, the GS benefits the most is probably new cams.. not OEM cams either.

I forget what's "SAFE" as far as an over bore. Its barely anything because the gs engine is already an over bored GS450.. only bore over if you HAVE too. you could shave the cylinder head, to raise compression, maybe run hotter coils, to run a hotter spark, then jump up to high octane fuels.. of course Springs+valves too.

that's how I'd go by it, without physically doing something like a turbo. I BELIEVE, you can kiss 70hp with a turbo though on the GS engine.

Let me start out with saying: find older posts by Burning1. He was (is?) a member here that raced the GS (and shared some great videos of him on the track).

But I think anything you do will come with a hefty price tag. I'm assuming your suspension is top notch already? You could try Mikuni mechanical carbs (VM or TM), or upgrading your exhaust headers (don't the stockers have flow issues?).

Aside from that, I think Megacycle makes cams for the GS. And Wiseco used to make larger pistons & sleeves. You might even find somebody that makes larger valves too.

Whatever you do, good luck and keep us updated!

Have you looked around gstwins.com?

http://gstwin.com/racers_corner.htm

A good job of jetting, intake, and exhaust mods will net you about a 10% increase in HP like Annie's (forum owners wife) GS.

http://img.photobucket.com/albums/v443/jcp8832/AnniesGS500dynoRun-1.jpg

You'll need a big buck change like a 4 valve/cyl head to do much better than that.

If you want my honest opinion, I think for a track bike you're better off taking the money you would spend upgrading a GS and buying an 04+ GSX-R600. Unless you're specifically trying to race in a 500cc series, in which case an EX500 is probably a better performance/dollars value (though, I do think they're rather less aesthetically pleasing than the GS500F). CBR500R is probably also a good choice, but a bit more expensive and less plentiful on craigslist.

All that said, if you're upgrading the GS simply because you like the GS, more power to you. But, like J_Walker said, whatever you do is going to be rather expensive.

Bob Broussard also had some amazing posts on his bike.
Dgyver had a very cool one that I saw, not sure what he posted.
But more power via rpm is the way to go, not via compression. Compression gets you torque @ low revs.

There is solutions to both as long as you're willing to throw $$ at it.

Cool.
Buddha.

I've seen Burning1's videos & build, and a few others but I don't recall anyone having dyno numbers. The only build that I've seen with hp numbers is a bike from the Bay Area riders forum... that bike had a titanium subframe, a long list of trick parts, and a lot of motor work. I'm definitely not planning to go that far.

My GS was a running Craigslist project that I picked up for $260(had speedo cable & countershaft oil leaks, rotted tires, and bumps/bruises), so it's just a cheap option to get back on the track. It'll be raced in classic 500 against a few EX500's.

im rackin my brain but there WAS a hi comp piston set that would work on a gs longblock. there was also a guy here that took the 2 centre cylindders from a gsxr. THAT was a buildup. stock i think the gs made around 42bhp? do you have any idea what youre wanting to do power wise? what numbers would be your ultimate goal?
Aaron

Has anyone tried intake porting and hotter cams?

The stock EX500 is 50hp, pipe + filter + jetting= 52, and 60+ with a built engine. If I could get the GS in the 50-52hp range without spending a fortune then I'd be happy. I spoke to someone at Bill Bune Ent and the valve job & head porting would be $300, and the GS carb boring is $100(gsxr carbs are $300 on ebay)...those 2 things don't cost much but I'm not sure how they'll perform with the stock cam. The build starts getting pretty expensive when you add the cam and high compression pistons, etc.

Higher compression will get you low end.
Oddly on a bike with a 7500 rpm redline (my MZ 660) I still didn't care for it. My stock MZ was better. It seemed to rev up quicker.
GS may be different, its a revvy bike. MZ isn't.

Cool.
Buddha.

Quote from: D_alexand_7 on July 30, 2017, 02:49:00 PM
I'm trying to improve the performance of my track bike without making it a time bomb. Has anyone here done head porting, cylinder +1 or 2 over bore, and/or had the carbs bored? Do you have pre and post dyno numbers showing the gains?

The bike has already been put on a serious diet and a lot of chassis upgrades, but only has a slip-on + K&N lunch box at the moment... it needs more power. I wanna bridge the performance gap between the EX's and the GS without spending a fortune. Any info is greatly appreciated.

http://www.eurospares.com/munn.htm
You could add ram air
This article is an old school one about a GS500 and a racer