i hope someone can help me out.
i acquired an 87 warrior in great shape, but in the middle of an engine rebuild.
anyway, it has been bored .020", wiseco piston and rings, new stock cam, timing chain, crank, and rod. i bought a service manual, and have the engine reassembled and back in. it runs, but i need help with the carburetion. it has the stock header pipe, but has a supertrapp muffler assembly, also has a k&n air filter and the air box has been ventilated with 6 foam vents. the carb has been changed to a mikuni 36mm round slide.
it starts and idles fine, and runs great at low and mid throttle, but when run harder at w.o.t. the exhaust pipe/muffler get very hot.
the spark plug looks ok, but with the fuel that is sold today with the ethanol blends it is very hard to tell fuel mixture by plug color anymore.
can anyone give me a general starting point for the main jet size to use?


thanks in advance.

 

I always use plug color to adjust my fuel mixture. Shooting from the hip I'm gonna guess around 142-148 depending on airbox lid on/off.

 

You can do WOT and choke it a tad - if it does better then you are running lean.
If you notice that the engine is stale or really struggling or has a flat spot at the top end then there is a good change you are rich.
A good running engine should pull progressively and smoothly until the limiter is reached.
A plug chop is pretty accurate way to tell even with the bad quality of gas these days.
To do a correct plug reading to include a chop. Put a used plug in and let the engine warm up good. Shut it down and put in a new plug, start the engine and WOT - don't let it idle unnecessarily. At the top speed kill the engine and get into neutral, stop and pull the plug out. Do your reading of the color. If you want a chop reading then cut the threads off the plug and read the base of the porcelan. It should be a medium to dark brown. Any lighter then go to the next larger jet and leave it. Better to be a tad rich. If it is black or almost black then a smaller jet.
You also can increase or decrease the air flow to change the mixture. More air - leaner, less air - richer.

Here is a good link for Q&A for you to read
http://www.dfn.com/benkaren/jetfaq.html

 

thanks guys!