The carburetors have an adjustable brass idle mixture screw. The adjustment screws are pointed on the end and as you tighten them into the seat they shut off the fuel for idle. As you adjust the screws back out, they regulate how much fuel is mixed with the incoming air at idle. There is usually some starting point like 2 or 3 turns out. You set them at that starting point. You start the bike. After it warms up, you adjust them in or out a little for the fastest or smoothest idle with no backfiring.

The screws are recessed down into a hole in the carb body. Because of emission requirements, they are set pretty lean at the factory and then an aluminum cap is pressed in to cover them so they are not tampered with.

Whenever you make changes like different air filter or exhaust, it upsets the idle mixture so these screws need to be readjusted. The same thing holds true if you tear down the carburetor to rebuild them.

There is an article at the top of the Technical forum dealing with idle jets. It has instructions on how to drill a small hole in these aluminum caps and then thread a sheetmetal screw into the cap and use a pair of pliers to pull the caps out. Once they are out, you have access to the idle screws. You can then make adjustments to the idle screws.

Generally when the bike goes lean you get a backfire.

Hope that this helps.

 

more info and symptoms

Ok, there's more...i've now found that a previous owner has drilled holes in the airbox where the air filter fits. I would expect this to affect both cylinders. Also, I decided to start it in the dark, or at least at dusk and i saw a blue flame from the exhaust form the front cylinder.
Can someone please point me to the location of the plugs over the a/f screw.
I can see the carb for the front cylinder ok. There is a screw near the bottom which turns freely but doesnt seem to do a thing. about 2" up and slightly to the right there appears to be two bulges in the metal that meed at which might be this aluminium cap.

Another dumb question: Can these screws be accessed without taking the seats, tank off the bike ?



Remember: Your not drunk if you can lay on the ground without having to hanging on !

 

Look here Mr. McIntosh:

http://www.dynojet.com/pdf/1152.pdf

On page 2 there is a drawing of the side view of your carbs. In this drawing, the location of the A/F idle mixture screw is pointed out. It also includes the text of the rejet instruction sheet. I would recommend backing the screws out 1/4 to 1/2 turn at a time, riding the bike after each adjustment to see what the adjustment yields. You will need to drill a small hole in the covers over the A/F screws to gain access to the screws. I found leaving the covers in place and inserting a small screwdriver through the hole to make the adjustment works best. If you remove the cover like the jet kit's instructions call for, you'll have to insure the screws can't back out on their own and fall out. There are myriad methods to accomplish this, but a dab of RTV silicone in the pocket around the screw works well. I don't think you'll have to remove the seat and tank, but if your '94 is like my '95, the horns will have to come off. Access to the screws is behind the horns. I hope this answers your questions or at least gets you started in the right direction.