'99 RM80-- Having a hard time getting it dialed in

[fiber_tek]

Son's bike.

 

We seem to be stuck trying to get this bike running right.  When cold it takes off pretty good, but warmed up it bogs really bad.  We have messed with the pilot circuit quite a bit and thought we had it set right, it would get the highest idle at about 2 1/2 turns out.  I think we have the main jet right.  WFO down our road, pull the plug and it is like coffee with creamer in it.  The needle seems right.  In 3rd gear roll it from part throttle to half throttle and it is smooth.  The bog at take off is pretty bad, and after my son rides it for a while and shuts it off, then tries to restart it within a couple of minutes it won't start.  The compression is good, we just went through the top end, and cleaned out the power valve when we had it apart.  We recently switched from 32:1 with Belray H1R, to a 50:1 mix.  That cleared up the oil spooge problem and seems to have made it run a little fatter/richer.  So we went down a main jet size from 190 to 185.  We are at 4000 feet, the bike has a UNI filter, Boyesen Reeds and has been bored to .040 over.  Also it is missing the mud guard on top of the air box, not sure if that affects jetting but I thought I would throw that in there.  Does this problem point to a weak coil/ignition, or something besides jetting?

 

Thanks for any and all help!

 

Jason

[Beau 88]

The hard to start sounds like a lean pilot , never change premix ratios to correct spooge , pick a good oiling mix and jet accordingly i run 32.1 Only . 

[fiber_tek]

Thanks Beau.  We got it warmed up really well this evening and tried playing with the pilot screw adjustment.  It seemed to have the highest RPM between 1 1/4 and 2 1/2 turns out, but the idle got really erratic.  I will clean the carb out really well, change the mix back to 32:1 and start over at the the pilot jet that the manual calls for in a stock configuration and go from there.   This problem did seem to get worse when we went to 50:1. 

[fiber_tek]

Took the covers off the sides of the engine and found the crank bearing was really worn out on the left side.  Rotor was rubbing on the stator, and the slop was causing an air leak in the seal.  Tried getting the rotor off and snapped the crank.  Manual said left hand threads, so was using a breaker bar the correct direction and the nut was seized to the crank and took the end of the crank off with it.  Good times.  Now looking for a complete bottom end. 

Edited June 18, 2014 by fiber_tek