70 Yamaha idle problems

[Kevin Nemeth]

" My motor 1989 Yamaha 70 hp w

" My motor 1989 Yamaha 70 hp won't idle in gear, it stalls warm or cold but runs ok when running at higher speeds.The dealer has done the carbs and swapped the CDI module.It will idle with scew cranked up to 1300 rpm in gear and drops down to 500 when shifted into gear. Compression is ok, plugs ok but they claim middle cylinder makes no power at idle. Need help. Any suggestions would be great. "

 

[ntbassman]

" Kevin,
I would suggest rem

" Kevin,
I would suggest removing the cylinder head to visually inspect the condition of the cylinder walls, piston crown, and rings. I have rebuilt a few yamaha's that compression was good, but a visual inspection revealed severe scoring on the cylinder walls, which caused the problem. Motors would run excellent at top end and mid range, but would shut off when brought back to idle.

Also check to make sure that the reeds are in good shape and are working properly. Hope this helps! "