70 Yamaha won't idle

[yam 70]

I have a 1989 70 hp Yamaha and left some fuel in it for an extended period.Had a hard time starting it and now it runs a little rough at mid throttle but the problem is it wont idle. I sprayed some carb cleaner in each of the carbs and they all reacted the same.When I take the # 2 and #3 spark plug leads off there is no change,but when I pull the #1 lead off, the motor slows down and runs smoothly .The timing is correct. I did a compression test at only 1500 RPM and all 3 readings were 120 PSI.

I just don't understand why that lead on number 1 makes such a difference. Seems like it could be electrical instead of carb. Any ideas?

 

[kandil]

Re: 70 Yamaha won't idle

You need to clean the carb the spray cleaning stuff is not a good way to clean a carb it could damge any rubber that it touch you need to take the carb a part and soak it in some fuel and spray some compressed air in all the small holes or the carb cleaning in all the holes if you don,t have air and make sure you don,t get the carb cleaner on any rubber gasket or it well deform and you can not reuse it it might be even better to get a new carb kit good luck

 

[yam 70]

Re: 70 Yamaha won't idle

Thanx for the advice but I think this is now real serious.

I did a leak down test and while all readings were 120 at only 1500 RPM,I noticed on number 3 the needle sinking down to about 60 which means, I assume that the problem is either sticking or broken rings,or a badly scratched cylinder wall and this means ripping the thing apart. Geez-I am not happy!

Has anyone done their own ring job before -It sure looks hard?
I will try some ring free stuff for drill but the way my luck has been going lately I am not betting on it.