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Ask Jeff Policky Your Own Question
Jeff Policky
Jeff Policky, Motorcycle Mechanic
Category: Motorcycle
Satisfied Customers: 2425
Experience:  Yamaha Gold, Suzuki Gold, Honda Bronze, Polaris Bronze, BRP
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my motorcycle does not idle, I need to keep reving it for it

Customer Question

my motorcycle does not idle, I need to keep reving it for it to stay on. And as soon as I let the rpms drop the engine shuts off. How do I get my motorcycle to idle?
Submitted: 8 years ago.
Category: Motorcycle
Expert:  Doug E. replied 8 years ago.

Does it run ok above an idle? Does it seem to be flooding out or is it running out of gas? Does it make any difference when you turn up the idle screw? Did you remove all of the jets and soak the carbs and jets when you cleaned them? Was the bike sitting a long time before this?

Customer: replied 8 years ago.
It runs okay above idle, you can keep reving it or hold it at 3000 rpms. It is not flooding with gas, it seems like the gas is not going into the engine on its own and that part of the reason why I need to keep reving it for it to stay on. Its not the idle screw either. I had the carbs cleaned out and when I did the mechanic said they were not that dirty to begin with. He cleaned them with a compressed air gun and different sprays, he did not soak them. and the bike was sitting for about a year before I got it. It is in very good shape, it only has 5000 miles on it, so that leads me to believe that the parts are all fine.
Expert:  Doug E. replied 8 years ago.
I suspect the pilot jets or their passages are plugged. Sprays and compressed air will not do the trick if varnish has built up in the passages. If the air mixture screws were not removed, that is another area that will cause the same problem.

The pilot system handles the mixture from 0-1/4 throttle and is the smallest jet in the carb. That is why it is always the one that causes the problem.

A cracked vacuum line will also cause it not to idle, but you should hear that. Double check all of the hoses and manifold for leakage.

If I had it in the shop I would pull the carbs and all of the jets and soak them in Yamaha carb cleaner. I would then inspect all of the lines and fittings for problems. This is a very common problem on any bike that sits. The gas turns to varnish and can clog the backside of the jets where you can't see it and where sprays will not reach.

Let me know what you find.

Customer: replied 8 years ago.
the problem doesn't seem to be with in the carbs, I had them professionaly cleaned a few weeks ago. I checked all of the hoses and they are all fine. The bike hasn't had to much exposure so everything is in fairly good shape.
Expert:  Doug E. replied 8 years ago.
The low mileage is irrelevant. The bike is nearing 30 years old so many parts could be bad just from age.

If it isn't a fuel/carb problem then the only other area to look at would be the compression. Have you taken a compression test? If not, I would do that. You may have a tight valve, although it would take several to keep a bike from idling.

There are no ignition parts that I know of that would allow a bike to start and run but not idle. You can confirm this with a spark tester or by using a timing light to observe the spark.

Does the bike idle if you put on the choke a little? Were the carbs synchronized when you put them back on? Are you running the stock airbox?