In the spring of 1990 I purchased my first KL650A, a 1989 model with less than 500 miles on the speedometer. The first thing I did was execute a complete set-up and service which exposed so many defects that I almost sold the bike.
What I did about the problems I encountered have been documented in Dual Sport News starting in the late 1990’s, as well as on 2 websites:
www.multisurfacemotorcycling.com (now defunct) and www.topgunmotorcycles.com.
The first thing I did was to check the valves resulting in the discovery of a stripped out and split 6mm x 1.0 right front valve cover bolt hole. Kawasaki reluctantly warrantied the head because the damage wasn’t repairable. Warning: after “time certing” the right front fastener hole, do not over torque the four 6mm valve cover bolts.
After setting the valves I went to the air intake system and discovered the foam factory air cleaner was, as usual, of poor quality and beginning to break down. I was forced to replace the old unit with a new factory air cleaner because the aftermarket didn’t have one for the KLR. I immediately called “UNI” and talked to a guy in the R&D department. I convinced him that the KLR needed a better quality serviceable foam air filter. The gentleman (whose name I have forgotten) told me that if I would ship him my air box complete with the stock air filter, he would design a UNI filter for the KLR and send me the first two off the production line along with my air box at no cost. To this day I use only UNI filters on multi-surface rides and K & N air filters for pavement only duty. (Installing a K & N filter may require slightly richer jetting.)
The main point of this article is to attempt to convince you that factory air filters are often of poor quality and need to be replaced. I don’t have recent first hand experience with factory air filters on other makes and models, but the filters installed on the DR650’s and KLR650’s are constructed of cheap foam that breaks down quickly.
Do your multi-surface motorcycle a favor by installing a high quality aftermarket air filter in your air box, service it regularly, and your engine will live a longer and healthier life.