How do the heat ranges affect our conversion motors. For example, I have a Ryobi that I converted that had a Champion DJ7J in it. Got a lot of interference and the motor likes to stall sometimes if come down to idle too fast. I have just ordered some Champion RDJ8J plugs for it. This is one step hotter and has a resistor that I hope will stop the interference. What is the opinion of the experts here on the hotter plug?

Thanks
Jim

The heat range really depends on how you are using the engine. The stock DJ7J plug is for weed eat'in or what not. It is intentionally colder to prevent the weed eater from dying before it gets out of warranty in case some one uses it in rather extreme conditions.
If you are going to fly the conversion, it could stand to have a hotter plug. The engine will potentially see more cooling traveling through the air. Depending of course on how the engine is cowled. The Champion RJ-8 is a step in the right direction.
The resistor should help curb radio interference from the ignition system.
If you use the two needle carb, you can tune the engine to run just about perfect through all the rpm ranges. They transition better than the single needle carb and definately worth upgrading.
Gary

First of all, stay within the heat range that the engine was designed for. For interference suppression (nothing to do with heat range) Change to R-type plugs. Some ignitions need the R-plugs, whilst some abhor them. You need to find out by trying, or something as simple as a phone call.
Most engines have a patent pending on the ignition system. Go to http://www.uspto.gov and find the patent that describes the system you have. Loads of information there.

Thanks for the info guys. Last night I went through my stack of motors to see what heat range plugs were in them. I have a pile that a local repair shop gives me every so often. My pile was about evenly split between 7 and 8 heat range plugs. I think I will go ahead and try the 8. As a matter of fact, my local supplier dropped off another 5 engines last night. Had to tell him that I now have enough weedies to last a while but to keep a look out for some larger chain saw motors. Probably got somewhere around 20 free weedeater motors now. Mixed lot of Poulans, Ryobis, and Homelites.


Jim