Surging at low RPM's

A lean cylinder would run hotter, not cooler. The difference in cylinder temps may be caused by the carbs being out of sync. One cylinder is running faster than the other. That might also be contributing to the surging. It's also possible you didn't get the idle circuits totally clean, or maybe they have partially plugged back up.

Often when you clean a really dirty set of carbs, try as you might, you don't get all the gunk out. Once you put them in service, the bits you missed can break free and plug things up again. This happened on the '83 I'm fixing up. Like yours, it sat for many years and the carbs were pretty gunky inside. I thought I had them really clean but once I started running it, the right pilot jet plugged up again on me not once but twice. After that second time it's been good now for quite a while. Hopefully it will stay that way and the carbs are really finally clean inside, lol.

 

When I have seen fuel leaking back into the airbox it has been due either to a sticking fuel level valve or the fuel level being set too high i.e. float levels wrong. I suggest you recheck the carbs as per 5twins suggestions and also double check the fuel level in each carb.

 

Fuel leak stops when the mix screw is turned in? That's a new one on me. Open that carbie again, as 5twins suggests give it another cleaning, check to see that the washer and O-ring are in place at the bottom of the mix screw casting (and that one and only one of each is in place), that the plug is in place at the bottom of the pilot jet casting, that the float has not taken on fuel if you still have the OE 1980 brass floats, and that float level is set correctly for the float set you have. Then synch.

 

Just you wait til your lady spots what you have done with her best stainless steel mixing bowl.....

 

Someone corect me if im wrong but what we commonly refer to as mixture screws are an air bleed adjusment. They work in reverse of what you would find on an automotive carburetor. Turning the screw out leans the mixture ratther than enriching it by allowing more air through this circut . Have to agree with 5twins, even after a thorough cleaning or two gunk can re-lodge in these passages. Especialy.Small ones like the air bleeds. As you said adjusting these screws had little effect it sounds like this could still be the case. And as he said, lean= hot. If the bike is in stock form I doubt that the larger jets are neccessary. Just get what you have dialed in. These bikes are the most fun to ride when they are running tip-top. So while repeatedly removing and going through carbs can be a pain, it goes faster and smother each time and can really pay of. Thats my two cents. Good luck and have fun.

 

No, the mix screws on these aren't air or "air bleed" screws, they control true fuel or, more correctly, fuel/air mix flow. But yes, turning them in does lean the setting. It lets less of the fuel/air mix in.

 

Thanks for clearing that up. Thats why I love this forum.

 

Rule of thumb: if the mixture screw is located in front of the slide tower, it controls vacuum fed to the pilot jet: out=more vacuum=more fuel=richer mixture. If the mixture screw is located behind the slide tower, it controls air feed to the pilot circuit: out=more air=leaner mixture.

The above is true of Japanese carburetors and of every motorcycle carburetor I've seen. I haven't seen everything, so if anyone knows of exceptions, please jump in!

 

Hey thanks. Makes sense.