I have a 91 300 4X4 and it is running too rich. When i open the throttle, it blows black (not blue) smoke steady. If i hold it wide open it will back fire. and send flame out the intake side. Has anyone seen this before. I have checked the valves, and checked the carb with no success. I am leaning towards the timing. I am thinking it might be the float valve as well, but it looks alright. Any ideas from anyone ?

 

How does it run at low speed, I have never seen black smoke come out of one, check the spark plug, tell me what it looks like, what is your wheeler a honda, if it's a 4 stroke it shouldn't smoke that much if any at all, when it's running does it blow oil out of the exhaust, if it is the timing, do you know how or where to adjust it, reply to these questions and I will see if I can help.

 

The plug is very carbonized with black soot. The idle is a little eratic. All the jets are not plugged. The float valve looks good, but that does not mean to much. Any ideas ?

 

If you think it is running rich, check and make sure your choke is not stuck closed, check your float valve, try lowering your float level, make sure your air filter is clean and oiled.

 

The air cleaner is clean and oiled. The float height looks good. They are not adjustable on this Honda. I might just try a new float valve.

 

If it is blowing black smonke out the exhaust you may have a valve promlem, usualy when they blow black smoke the valves are not closing all the way, it could be timing too.
Do you know how to set the timing on it..
Does it have a cover on the left side(as your sitting on it) that says cdi on it.