Bad idle - Yamaha 15 HP 2 stroke ENDURO

[Monique]

Hello Gang,

A mate has the engine listed above. It will not idle properly and requires some choke to keep it running.

I've removed the carb, cleaned the components including removal and cleaning of the jets and float. The fuel filter was also cleaned; had a small quantity of sand in it. I also changed the plugs.

To no avail; has anyone experienced this? What is your fix? Thank you as always.

 

[CliveF]

So its running lean.
Either you missed something and enough fuel is not getting through

or your butterfly is not returning to the correct tick over closed position.
Remove throttle cable from carb and check that the butterfly is moving silky smooth. I had to oil the top and bottom pivots after a minor dunking stiffened it up.

Once moving smoothly again enough lube should come from the fuel.

Regards Clive

 

[geem]

Hello Gang,

A mate has the engine listed above. It will not idle properly and requires some choke to keep it running.

I've removed the carb, cleaned the components including removal and cleaning of the jets and float. The fuel filter was also cleaned; had a small quantity of sand in it. I also changed the plugs.

To no avail; has anyone experienced this? What is your fix? Thank you as always.

I would suggest cleaning the carb again. Possibly some dirt has been dislodged from somewhere and it is blocking a jet again. It sounds very much like fuel starvation

 

[lw395]

If it won't idle, then it's possible the bores, rings or crank seals are not happy.
Other possibilities include an air leak, such as from a worn carb spindle.
But a dirty idle jet is always favourite.

 

[LadyInBed]

On 15hp is it a butterfly or needle valve?

 

[Boathook]

I had that type of problem on my malta. Very small amount of muck in the idle jet. Very difficult to see so maybe use a magnifying glass.