92' Yamaha 85 Mid-range problems

[ssimonen]

My 92' Yamaha 85 has problems with acceleration. Idles well. Full speed is good. Getting up to speed it bogs, but only briefly. Some have told me it's my prop, others said replace the plugs. It just came out of winter. It did not have this problem last fall.

 

[jim dozier]

Re: 92' Yamaha 85 Mid-range problems

I am assuming this is a carbureted engine. Since it runs good at WOT its not your fuel pump or main jets. Since it also idles well its probably not your ignition either. It may be that you are a little too lean on your idle circuits. Most engines are supposed to be set about 1/8 to 1/4 turn richer on the idle mixture screw than optimum idle. This allows for a better take off. It could be that your initial setting was a tad too lean and combined with some minor gum deposits from the previous winter you have now gone over the edge into too lean territory. Short of a complete carb rebuild, try opening your idle circuits 1/8 turn on each carb and see if it helps. Also check for any air leaks in carb gaskets or fuel line connections from the carb to the tank. Air leaks could lean out the mixture also.