Yamaha 8hp uneven running

[labougie]

My 8hp 1992 Yamaha Enduro (same as the earlier 8B) stutters and misses at certain throttle openings. Tickover is fine (although a little smoky, even at 75:1) and half throttle and above is perfect. The problem is between tickover and half throttle where it runs unevenly. I can't think that it's an electrical problem because it only happens at the specific throttle opening. I'm very poor on carburettors - is there a jet controlling this specific throttle range? Is it adjustable? Thanks in advance.

 

[ctva]

Sounds possibly like the main jet needs cleaning, that's where I'd start. Ive got a Yam 8 and cleaning the carb is not too onerous if you can get a look at a diagram which might be able to be found on line. Other obvious places to look at are the fuel and air filters.

 

[rotrax]

Sounds possibly like the main jet needs cleaning, that's where I'd start. Ive got a Yam 8 and cleaning the carb is not too onerous if you can get a look at a diagram which might be able to be found on line. Other obvious places to look at are the fuel and air filters.

Pretty much what a partially blocked jet does.

Experienced the same earlier this year with my Evinrude 6hp twin. Left it unused for four weeks and the main jet gummed up. It needed a good poke with a small diameter wire to shift it. Sticky green stained-from the 2t oil I use-muck that was left after the float bown fuel had evaporated during the good spell of hot weather while it was unused.

I shall drain the bowl before I leave it again.............................