Engine mod for ultimate Street race GS!

[Filipe_500]

[Travis R]

I'm going to go out on a limb and say that it's vibrating a lot because you changed the weight of the counter balance shaft and didn't change the weight of the crank/ piston assembly (you didn't mention any).  It will always vibrate until you re-match their weights... by either installing a stock counter balance shaft, or by shaving weight off the crank to match it.
It definitely a cool looking bike though!  
Good luck

[falcon0321]

- What else could I do to get more power from my GS500?

Buy a 600... I have one for sale.   99 F4, its Listed in the for sale section.  

With the lightened counterbalance and the vibrating engine you run the risk of breaking engine mounts.     Nothing bad will happen you will just have to re-weld them.  

I would consider buying high compression pistons.   It looks like your head has been hogged out to make a bigger combustion chamber, this will lower the compression... less power.  

Also dropping to a stock 16 tooth fron sprocket will help or even drop down to a 15 tooth.     the highest you could probably go is a 15-43 combo and still be able to get up to 100mph,  or at least a decent street speed.  

I have a friend thar had done similar mods to his race gs and had 53 HP with pump gas and a 8:1 compression ratio.  Get higher comp pistions and run VP or and you should be gettting around 60 HP  but it will probly blow up within the year.

[Jake D]

You could easily increase the displacement.  Or go to a four valve set up.

Does anybody remember the name of the guy that build the 4 valve race GSx- 500?  

It escapes me.

[V8Pinto]

Nice bike.

If you're building a stoplight racer, definitely go lower on the front sprocket.  As long as you don't ride any freeway, you could go as low as a 14.  Of course, you could still go on the freeway but my grandma would pass you.

Why not stick with the modified counter balancer and rebalance the reciprocating assembly?  (I'm not speaking from my GS experience so I'll duck any flames   )

Stoplight to stoplight you will do good on the GS.  I take everybody off the line at the drags including race prepped literbikes - but it's over real quick  :lol:   You won't have a lot of hump but you'll get the jump.

[dgyver]

....Does anybody remember the name of the guy that build the 4 valve race GSx- 500?....

Cedric and Bob Broussard.

maybe next year my name will be added to the list.


The 190 rear is not helping at all. There is a lot of rotational mass with a tire that size. Unless you are putting out over 120hp, fat tires are just for show.

[Filipe_500]

[Jake D]

The GS head and the GSX-R head is the same as the GS head, except with an extra cylinder tacked on to the outside on each side.  You get a GSX-R head and have the two outside cylinder's chopped off.  The gasket is the same and everything.

But I've never done this.  It is merely my understanding.  There is like a 50% chance I'm wrong.   Cedric doesn't come to this site, I don't think.  But Bob B could give you more information or dygver.  He is building one now.

[bcutrufelli]

I have to admit that you have a nice bike.. There is a but I will have to include.  It seems like you or your mechanic is building a motor with hearsay mods.  If you shaved the head to a certain amount, Why do you not know the effect? same with all of the other mods you have done.  You should be telling us HP numbers not asking.  You need to research what you are doing better.  Its like a few people I know that got port and polish done by people they knew but have no flowbench testing and have no idea what the new measurements are.  Do your research and dyno test as much as possible.  For street racing you will need nitrous to be even remotley competitive.  Again  i am not trying to be a jerk but seriously research what you are doing before modifying.

[funwithtwins]

Its a nice bike i like it. I see the "its still a gs" alot here when shown really nice modded bikes, which is all good, but why do so many seem against to much modification on the gs. I do understand that it would be easier and, would have more power to just go buy a bigger bike but if major mods are not appropriate why would any mod be appropriate. I look at it like its my bike and even it modification in its most severe deep down any mod just makes you feel better about an allready great bike, and thats what any mod is about right that feeling that you get right after its done, that its just a littler faster than before who cares what it cost or how much time and effort it took. Right?

[Filipe_500]

[Rema1000]

On this site, in the "Racers' Corner" ( http://www.gstwin.com/racers_corner.htm ), there is a recommendation to remove the counterbalancer altogether.  But then, you need to have the crank rebalanced; and it will _not_ be as smooth as stock.

So, if your mechanic rebalanced the crank after shaving the counterbalancer, then maybe he did a poor job.  If so, then you need to find someone who can rebalance it better.

If your mechanic didn't rebalance it at all, then you could either put a stock counterbalancer back in, or else find someone to rebalance the bottom end.

[V8Pinto]

Yes you can add material back by welding but in your case I would say it's not worth it.  The usual case for this is offset grinding a crank to add stroke to the motor.  I think you're on the right path to install a stock counter balancer.  

I might turn down the O.D. of the generator in a lathe to get a little zip out of things.  Don't go all crazy with this suggestion (little dab will do ya).  The effects of weight reduction change by the square as you increase the diameter so the generator is probably a better place to get gains than the counter balancer (unless you're looking at removing it alltogether).    Part #2 in the "generator" schematic on bikebandit.

Polishing in itself doesn't hurt compression but removing any significant amount of chamber material has the opposite effect of milling the head.  There are other effects that can improve flow within the chamber but those effects would probably be second order.  I can only speak to porting car heads.

[Filipe_500]

hi all,

Just got a new counter balance!

Have a question tho.... This cristimans I was thinking about drive my bike to my parents house, which is around 90 miles away from mines....
do u reckon I could be putting my engine in risk by drivin over there with this vibration? (suposing my counter balanced is not balanced with the crank)...

thx

[Blueknyt]

dude, before you put that CB shaft back in, i was gonna suggest sending your crank, rods and pistons off to falicon and have them ballence the crank and get rid of the CB shaft, it might be alittle buzz, but not rattle your teeth out vibration, and it will allow the crank to spin up faster.   last i talked to them its like 210$ to ballence the crank plus shipping/crateing

[Filipe_500]

[falcon0321]

Could be that the gaskets, rings, or valves arent sealing properly.  It might
just be that your timing is off and the valves arent closing when they should.

You may need high comp pistons becuase of metal you took out of the head.

No offense to you but taking the bike to someone who knows what they're
doing helps alot.  They know all of the little tricks that you dont.  You will
have a hard time mixing and matching all of the mods.

[Filipe_500]

heheh... the problem is that i~m takin the bike to the best mechanic around, but he keep on doing this shits.... so I have to search around to tell him what not to do  :guns:

[Blueknyt]

squirt some oil down into the sparkplug hole and see if the compression comes up alittle, if it does then its rings, if not, its valve related.

[MX304]

First off, great looking bike. I have two questions. What kind of tail is that? How in the hell did you get a 190 tire in the stock swingarm and get the sprockets to line up?