Join Date: Nov 2009
Location: Lander, Wyoming
Did you purchase this bike used?
Any chance that someone installed an automotive PCV valve into the crankcase breather hose, UP-side Down? That could cause a pressure build up.
Stock and standard vent system (just an open hose between nipples) works best on this large single cylinder engine.
The hole going into the air box by the top shock mount is only about 3/16-1/4 inch, if I remember correctly and does have a little foam filter stuffed into the nipple from the Inside! Don't blow it out with compressed air, use your mouth to check flow.
Modify at "YOUR OWN RISK"!
Still riding my 1987 KL650-A1. 78,000+ miles & counting