Thanks Guys for the data. I was thinking of trying the OS type f plug. That K&B 4 cycle plug looks good also. The engine was not purchased new...so I do not know what plugs should be in it. It seems to start good except on a very cool day??? I only have about 40 min on it. I ran it till it got up to temp....about 3-5 mi per run. Regards Capt.n