[AwwsChwA]

Ok, I'm hoping there's a carburetor whiz here who can help me with this. My 1981 GS450-S has a really erratic idle speed after the bike is warm. While sitting at stops, the idle will hunt all over, ranging all the way from barely running up to about 4k. Other times, it will idle perfectly at 1,500RPM for a few seconds, and then zoom up to as high as 5k. I end up having to kill the engine and restarting it. And even then, it won't behave.

My choke does basically nothing except on first start-up. Even when it's fully off and the engine is nice and warm, I can find certain spots in the choke range that will calm the idle down. But, that calm spot is not always in the same place in the choke range. Also, usually it will zoom back up after a few seconds of calm idle after I adjust it with the choke. Very strange.

Anyone have a guess as to the main cause of such a funky idle? I've never worked with carburetors before. Thanks!

 

[dirtyfingers]

POssibly a vacuum leak. Get some spray carb cleaner, and while the bike is running at a steady idle...spray some of the carb cleaner stuff at the rubber boots and clamps where the carbs fasten to the engine. If idle changes, you've found your problem. After years of abuse the rubber parts start to deteriorate and crack, allowing unwanted air to seep in. Don't try to patch it up with silicone, or glue. Get some new ones.

 

[sparty]

actually i have an 86 GS450L that had almost that same problem, i used to just slip the clutch a little bit with no gas while idling to make the revs drop. but what i found out was that i had adjusted the idle speed while the bike was still warming up, so i just turned it down a small bit after the bike was warm. also on top of that i found that my carb clams werent very tight, so tighting them up seemed to help a small bit. good luck

 

[Dave2122]

Sounds like the carbs need to be cleaned and as was stated you should make sure you don't have air leaks. Older bikes tend to have air leaks due to the rubber parts drying out. The carbs tend to get "crystalized and dirty. The carbs may seem clean to the eye but you must remember that the air passages within the carb body can be pluged with dirt.

Hope this helps.

 

[themeatmanlandry]

POssibly a vacuum leak. Get some spray carb cleaner, and while the bike is running at a steady idle...spray some of the carb cleaner stuff at the rubber boots and clamps where the carbs fasten to the engine. If idle changes, you've found your problem. After years of abuse the rubber parts start to deteriorate and crack, allowing unwanted air to seep in. Don't try to patch it up with silicone, or glue. Get some new ones.

What kinds of abuse? Possibly . . . spraying carb cleaner on them? :shock: