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**nabrams** · 09-24-2003, 12:28 PM

Hi,

Your problem could be related to so many things that are typical of bikes that have been sitting. So, I've pasted some of my advice in other posts here for you to read. It probably pays for you to investigate all of them, but I'd be paticularly suspicious of air leak and air filter problems (see below).
Also, you almost certainly have an idle jet.

I had mild back-firing during idle, warm-up, and higher revs. In my case, everything was running too lean (my plugs were VERY light gray). I had to do ALL of the following in order to totally get rid of the back-firing:

1. Adjust the mixture screw for max RPM at idle (I had to remove the tamper-proof caps). They should be between 2 and 6 turns out from bottom.
2. Clean idle and main jets with a copper wire (spraying tons of carb cleaner through them didn't quite get all the gunk out).
3. Install a proper foam air filter element (mine had disintegrated).
4. Seal ALL air leaks (no matter how tiny) at all boots and at air box lid.

Steps 3 and 4 above are just as important (perhaps more so) as steps 1 and 2.
Do all of the above and then move on to other areas if necessary (coils, timing, etc.).

In my case (1980 GS450L), the air filter element had disintegrated and there were tiny air leaks in various other places. I had cleaned the carbs (several times) and it would not run right. It was only after I resolved all the air flow and air leak issues that the bike ran decently. The CV carbs on our bikes are VERY sensitive to improper air flow.
You will drive yourself nuts cleaning the carb a million times (as I did) only to finally realize that the air flow (or leak) problems were critical as well.

Air leaks at the boots that attach to the airbox (containing air filter) can be just as bad as air leaks at the boots that attach to the engine. I know this because I had the same problem. My bike had been sitting. It would run at idle and stall when giving gas - just like yours. I cleaned the carbs several times. After sealing the leaks (with silicone), the bike ran smooth as silk. That airbox and air filter were designed for a very precise air flow rate suitable to your bike. Any air leak will throw the whole thing out-of-whack. The air filter element is critical as well. If it's rotted, you can bet you're bike won't run right.

On my GS450 the cross-over pipe (connecting the two main exhaust pipes) came off. This had almost no affect at high throttle settings, but DID have a very noticeable effect at low throttle and idle. I'm pretty sure the back-pressure of the exhaust system is an importatnt part of the equation (often ignored). Just as the airbox and air filter (and any air leaks at any of the boots connecting to the carb) are often ignored. I spent weeks fiddling with the carbs just to finally realize that it was my numerous air leaks and huge exhaust leaks that were the real problem.

Maybe this is obvious to you, but are you sure your floats are floating. They may have leaks. Take them off and shake them around near your ear. If you hear liquid sloshing around in there then you've definitley got a bad float. Leaking floats are quite common of these old bikes.

**Anonymous** · 09-24-2003, 01:03 PM

Nabrams,

Thanks for the great responce. This is my first "CV" type carb and the airbox tip is a big one. I have been testing it with the air box disconnected to speed the process of disassembly when it still doesn't work. I will go after the air leaks. My exhaust is solid..

What I was refering to is the plug shown in picture 24 of the GS carb cleaning article linked on the main page of this website. Mine did not have a plug covering the pilot jet. Is this "plug" a necessity? Most carbs I have worked on this jet is exposed to the fuel bowl.
Bill

**nabrams** · 09-24-2003, 01:54 PM

My 1980 GS450 does not have a plug covering it. If yours is a 1980 or later, it probably wouldn't have a plug covering it either.

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