Diagnosing a High Speed Miss
 

Diagnosing a High-Speed Miss
by Phil Stewart

One of the frustrations of a high speed miss is the difficulty of diagnosing it's cause. Following are some simple tests that may aid in narrowing down the problem:

Ignition Breakdown
<OL><LI> With the bike on the center stand and at the miss RPM (if you don't have a throttle lock [aka- cruise control], use a spring clamp or some other mechanical device on the throttle grip- your hand will not be steady enough, which will add confusion to what you are doing) try removing and reinstalling one spark plug lead at a time (pliers with insulated handles remove some of the excitement from this procedure) :) and see if all have nearly the same effect. </li>

Note-you may have to resort to actually running in gear, to put
a load on the engine so it will act up. If you do so, adding a restraint to keep the bike from launching should it vibrate off
the stand, or in some other way get loose, is advised.

<LI>Try gapping your plugs down in the 0.020" range and see if the problem moves RPM (test it while riding).</li></OL>
Fuel Starvation
Two things to try while your are riding in the miss RPM range (remember to keep one eye on the road during these procedures). ;)

<OL><LI>Try moving the pet-cocks to the reserve and prime positions.</li><LI>Try experimenting with the carb enricher (choke) lever. </li><LI>Try opening your gas tank (if the vent gets plugged you will experience gas starvation)</li></p></OL>