Re: Headlights with different wire colors!
Posted: Tue Nov 14, 2017 6:37 am
Clarence is making a valid point here. Unless you have been doing wide open throttle jetting runs, assuming the main jet is causing plug loading is only an assumption, and would not necessarily be right. It is quite possible to foul a plug without ever getting over half throttle. Search the Internet, or read the recommended jetting procedure, and you will find a graphic that shows how the various jets in the Mikuni overlap. Flow is restricted by the smallest orifice or most restrictive combination of parts. So while the main jet does supply fuel to the needle and needle jet, it isn't until the needle is lifted more or less out of the way that flow is ultimately limited by the main jet. Until you reach a throttle setting that allows the main to control flow, you could ride without a main jet at all, and still not necessarily foul a plug.
If your bike starts cold, at altitude, without the starter circuit, you either have the wrong pilot jet, or your starter circuit is bleeding fuel. If the starter circuit is bleeding fuel, no amount of jetting will fix your problem. When the starter circuit plunger is fully seated (choke off) there should be zero fuel passing through that circuit. You could have debris under the plunger, or the plunger rubber could be cracked, hard as a rock and unable to seal, missing entirely, or the plunger could be hanging up before seating. Any of these conditions would cause what you are experiencing, and none have anything to do with jets.
If your bike starts cold, at altitude, without the starter circuit, you either have the wrong pilot jet, or your starter circuit is bleeding fuel. If the starter circuit is bleeding fuel, no amount of jetting will fix your problem. When the starter circuit plunger is fully seated (choke off) there should be zero fuel passing through that circuit. You could have debris under the plunger, or the plunger rubber could be cracked, hard as a rock and unable to seal, missing entirely, or the plunger could be hanging up before seating. Any of these conditions would cause what you are experiencing, and none have anything to do with jets.