Yamaha runs full throttle, stalls at idle

[willclay79]

Have a late 80's Yamaha 6 hp two stroke. It has been to mechanics twice in a month for same problem. When started it idles for literally a few seconds. I have found that if I pull out choke full, twist tiller control to half throttle I can get it to pull start every time. I have about two seconds to put into forward gear, close choke and twist to full throttle and it runs great. Once I decelerate to idle it stalls again. No sputtering, just quits.

Ideas????

 

[Piratehooker]

Re: Yamaha runs full throttle, stalls at idle

I can't tell you specifically what it is, but it sure sounds like a lean condition on the low speed or idle circuit of the carb. What did the 'mechanics' say they did and was it any better when you got it back? Is it intermittent or is it constant?

 

[willclay79]

Re: Yamaha runs full throttle, stalls at idle

I tried adjusting both the rich and lean screws to no avail. but in reading more since doing so I might not have given it enough time as I hear it may take up to 30 seconds for an adjustment to take effect. The problem is constant not intermittent. What is the idle circuit you are referring to?

 

[Piratehooker]

Re: Yamaha runs full throttle, stalls at idle

Every carb has different circuits. Most have an idle cicuit, and then a low speed and a high speed, controlled by the pilot and main jets respectively. Obv there is a lot more to it, I would recommend getting the correct book for your carb and going from there. I bought a sled one time that ran great but would not idle no matter what. Turned out the pilot jets were clogged in both carbs.