Think I am running rich

[Guest]

I just picked up a 89 GSX1100F with a Vance and Heins 4 to1 exhaust, Dyna coils, and supposedly a big bore kit. Not sure about that last one though. It does have the stock airbox. On the ride home I noticed that it bucks and stutters at a constant speed. Its not like its uncontrollable or anything but it certainly is annoying. The bike accelerates fine and at low speeds it behaves. The problem comes at 1/4 to 1/2 throttle. If I accelerate the problem disappears. To start seeing whats going on I added a little choke (enrichment) to see if it was running lean and it ran worse so I am guessing it is running rich. The previous owner said the plugs were black when he looked last time and added a K/N filter to try and lean it out. So my thought was to start re-jetting the carbs leaner and see if that fixes the problem. I am also getting popping when I let off the throttle. Excess fuel? So I am going to try putting some smaller jets in there and see what happens. Any one have any thoughts? Experience with jetting a GSX for 4 to 1 exhaust with Dyna's?

[hikermikem]

Almost sounds like your pilots are too large - plug chops would give you more insight into what circuit is out-of-whack (assuming the issue is fuel related).

Unless you know for sure that the carbs are clean, it's a good idea to break them down & dip them & get new o-rings as well...

Of course then you'll know what jets (mains, pilots & air) you have, & what position the needles are at too.

Once you start with a "known" clean carb & jetting baseline," , it will be easier to remedy the symptoms you describe.

[gearhead13]

popping on decel is too lean on the pilot or mixture screw.

[bomber737]

I was planning on cleaning them. I have another 87 parts bike with carbs I have already cleaned. That bike also has a Kerker on it so I am going to compare the jets in it. And I know that bike does not have surging problems at speed. Any one know if these flat slide GSX carbs will fit on my GS1000?

[bomber737]

Ok I guess I thought it meant there was excess fuel when the throttle was closed. But I will put my color tune on it and see if they are set correctly. The pilot jet might be to small. I already downloaded the spread sheet with all he carb specs.

[bomber737]

While I have been running the bike around I have started cleaning the carbs I have from my 88 GSx1100F parts bike. I was going through the jetting chart on the Base cliff site to get the specifics. It lists the main jet at a 102.5 and my carbs have a 112.5 in them. I looked at the parts pit stop fische and they list the stock main jet as a 112.5 for those carbs. The bike has a kerker 4 to one. Has anyone found differences between the jetting chart and other sites? I plan on using the spare carbs on the bike while I clean the ones it is running right now. I will see what it has in it then. Or are there any GSX guys here running the kerker that can give me some guidance with what worked on theirs?

[gearhead13]

Those years of Gixxer carbs are known to oval out the emulsion tubes, creating a rich needle mixture. When you have them apart, take a close look at the top of them for out of round.

[bomber737]

I have been looking at the tubes as I get the carbs cleaned. They all look good and are nice and round. I have found that the main jets are 112.5 on the outers and 110 on the inners. This is what the parts pit stop fische showed. So I am guessing that the P.O. just threw a pipe on it and left the carbs alone. Dyna jet kit here I come