Modifying Jets in GZ Carburetor

[catchemall]

Just installed a 16 tooth drive sprocket today; sure does improve the drivability in the first 4 gears; haven't had a chance to stretch it out in 5th but I can tell it is going to be a load on the engine.

There is a kit listed on E-Bay from "6 Sigma Racing"; which modifies all of the jets in the carb; rather than just the High Speed jet.

Has anybody out there installed one of these kits or have any knowledge of how they perform.

I have not made any changes to the intake or exhaust; yet.

Thought I would try this kit first and see how much improvement it makes if any before modding the exhaust or intake.

The ask for specifics on mods made; altitude at which bike will be operated, etc. Seems to be an engineered kit from the description.

Would be interested in any information anyone can provide.

Thanks,

Jim

[JWR]

A lot of folks have tried to get "more" from this bike with dismal results.

There is only so much that you can squeeze from the GZ, that the results are not worth the effort.

Regarding the 16T, it does a good job, no hills or wind.

I use the 16T and the 15T, depends on what riding I am doing.

I think I will go down 2 teeth in the rear on my next sprocket, then the 16 should pull it OK???

Come on up when the weather turns.

Jerry

[Easy Rider]

Has anybody out there installed one of these kits or have any knowledge of how they perform.


There are a couple of threads about air/pipe/carb mods on here. At least one about the carb has very detailed instructions and good pictures. Do a little searching.

Having said that, however, while some who have gone "the whole 9 yards" seem to be pleased with the results, most will honestly admit that, in the end, it wasn't really worth the time and money invested for such a tiny gain in performance.

I loved my bike with the 16T sprocket and took it for a 1200 mile trip in the year and a half I had it but it is even LESS Interstate capable that way than it is stock.

[blaine]

16t sprocket works well for me but I only weigh 140 have intake,carb'exuast mods I recomend. All

[catchemall]

I installed the 16T sprocket and I really like the way it drives around town. Spreads out the gears and makes the bike more manageable in first gear, doesn't try to jump out from under you.

I'm not going to try to modify the carb or exhaust; I don't think the gain would be worth the expense and trouble; anyway, I don't think I would get on the freeway with this bike even if it would cruise at 65; gets a little light at that speed.

Presently shopping for a BMW R1150RT for road trips. Haven't decided if I will keep the GZ for short trips around town or go ahead and sell it. I really like the way it handles, can throw it around almost as easily as a bicycle.

[catchemall]

If this board will permit me> Attached is a very good article on the "Theory of Operation for
Mikuni SV Carbs.

If it does not upload: Google "Principles of Modern Motorcycle Carburetor Function" by Ken "The Mucker" Sexton; Aug. 2007.

Sorry: PDF files not allowed.

[Dupo]

I set the board to accept PDF attachments. Try again!

[catchemall]

Here we go again. By the way this carburetor is very similar to the Walbro Types used on small Two Stroke engines: in respect to the operation of the diaphragm controlling the mixture needle.

I use the Walbros on my Gas Powered Boats and the Needle setting, especially the spring tension which the needle has to overcome to open up is very critical in determining whether the engine runs lean or rich.

The article also states that just performing part of the mod; i.e., intake, exhaust, carb will not make a lot of difference and to really accomplish any gain you have to do them all.

Here it is if it uploads.

[Goose]

I looked up the kit from 6 sigma and the only kit I could find that they sell for the GZ250 only includes the main jet. They also include a few things that wouldn't make much sense for our bikes, like instructions for building a carb sync tool. (Only one carb, no need to sync) In reality, from looking at what's included in the kit, a little know-how, some reading on this site, and about $8 in parts from the moto shop and hardware store would get anyone where they wanted to go just as well as the $40 kit. For someone who doesn't want to take the time to research it, maybe it's a good idea, but all in all I'll save my $40.

[Black rider]

Hi there, could some one tell me what is the parts# for main jet 130-140.Thanks

[blaine]

There is no part number,just take old jet with you and get the one you want.They are marked what size they are. :rawk: :2tup:

[MadCityRider]

Anyone looking for one of these (or wanting to swtich back) I've got some extras:

viewtopic.php?f=11&t=4616 (http://www.gz250bike.com/forum/viewtopic.php?f=11&t=4616)

:rawk: