I am helping a friend set up his bike. His set up is:
DMP crank (the non stuffed version)
The mesh high flow filter
When we set up the bike we started the jetting a bit high at 96. Four stroked slightly, but I thought at least to start that would be safe, because the owner does not take it easy. Felt like it would need a 90-92, but I thought be safe for the first tank of gas. After getting it setup up rode about 10-15 miles and seemed to run good.
The next day he went to take out the bike and it would not go over 15mph. The bike is now four stroking constantly. We down jetted to a 90 and then a 88, and it now reaches 25 maybe. Feels like it would need to have something like an 82 in it.
So what could possible happen to make the big need to drop 14 jet sizes?
I thought maybe the timing had slipped and that it was full retard and just acting like it is rich. However time is still fully advanced, the sparkplug gap is stock and the spark is a nice blue.
I could not find anything wrong in the carb. The float is level, the float needle looks in perfect shape to me. We tightened the part the jet stews into (thought that could be loose and letting extra gas in.)
I am confused. If it was way to lean, then we would just have to search out an airleak, but I have no idea why it would after sitting overnight need a much much smaller jet.