Jetting your Carburetor

 

The only positive way to see if you are running too rich or too lean is to "read" your spark plugs. This is really quite a science but basically they should be dark around the thread area, gray on the electrode and the porcelain in the center of the threads should be tan colored on a Shovel or earlier, white with just a spot of tan on an Evolution or later.

Before attempting to rejet you must be sure that the entire intake area is sealed. To check this run the bike at a steady RPM (idle) and use water, WD-40 or PJ-1 to spray the intake area, if there are any leaks the RPMs will drop when the spray enters the engine.
If there is a leak, all seals must be replaced.

I have noticed a lot of Shovel riders are struggling with getting a proper seal at the head to manifold seal. Try this, use the wide rubber band style seals and a manifold adapter kit. (Here is an example pictured at the right) and use a generous amount of Hylomar (available at most automotive supply stores), use it to seal the adapters to the heads/manifold and the inside of the seals. Be sure that the carb or air cleaner is securely supported before tightening the manifold clamps.

To jet the slow speed (or intermediate) jet, after changing the jet, take it for about a five or ten mile slow ride (through town). After it is warmed up, if you notice any coughing through the carb it will probably be too lean. When you get back, pull the plugs and "read" them. If they are too dark then drop one slow jet size. If they are white on the porcelain or the electrode, maybe even a touch of pink, it is too lean. Replace the jet with the next larger size, go for another ride.

To jet the high speed, use the same process except this time test ride it on the highway, keep the RPMs up and then hit the kill switch and coast to a stop. Read the plugs along the roadside.

For help with spark plugs refer to:
Spark Plugs