Honda 15 spark plug fouling

seajackski

Recruit
Joined
Jun 2, 2008
Messages
4
I bought a pig in a poke on ebay -- 15 hp extra long shaft which fouls plugs so bad after 15 hours engine will not run. Cleaned carb, replaced mixture screw -- set to about 1/2 turn out now. Compression about 170 psi -- a little high. After short run time on new plugs they are classically fouled with carbon.
Folks suggest running full throttle to prevent fouling.
Other suggestions?
Thanks
 

gss036

Commander
Joined
Jan 18, 2003
Messages
2,914
Re: Honda 15 spark plug fouling

I don't think gas by itself will cause fouling that fast. How is your oil level? That is probably the same as my 15hp Honda and I have never had a problem with fouling.
What does the area below the exhaust look like on the rear of the engine? If it is really smoked up w/black crap on it then you are running too rich on gas. A 1/2 turn doesn't seem like it it out enough, but then I don't know that. Have you checked the float level in the carb?
I am having some problems w/my 15 but not fouling plugs.
 

hondon

Lieutenant Commander
Joined
Jun 11, 2001
Messages
1,922
Re: Honda 15 spark plug fouling

Once again it would be nice to know if you have a 15a or 15d as the end advice can be substantially different.Those compression #s are approriate either way.You will need to determine your idle speed either way as well,with an actual tach.15a set at 1100 warmed up in neutral,15d ,950,but give them a little longer to warm up.Idleing these units too slow or lugging them will cause your exact symptoms.What application are we useing here?
 

seajackski

Recruit
Joined
Jun 2, 2008
Messages
4
Re: Honda 15 spark plug fouling

Thanks for replies -- sorry -- been out of pocket.
15A.
Yes upper exhaust port gets dirty when running.
Will double check float level.
Oil level unchanged in 35 hours of running.
Thanks!
 
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