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Damn.  I knew it was only a matter of time before something would go south on my dirt bike.  I bought it used less than a year ago but from a total stranger.  Said stranger was a complete tool too, so I have no confidence in the previous TLC that the people gave to it.

Three weeks ago was the first ride I took since the summer down time.  Prior to that I performed what I would call a major maintenance - oil/filter, coolant, air filter cleaning. new rubber, greased a bunch of parts, etc.  Saturday was the third weekend in a row that I have ridden since then.

As we were wrapping up the ride and heading back towards the truck, my bike started to run poorly.  It stalled easily and actually had a spark knock when rolling on the throttle at times.  We were doing to single track as well and there were times where the bike was running hot, judging by the hissing noise coming from the radiators.

Because of my situation, we took the most direct way back, and when I rode the bike up on the trailer, oil was puking out from under the skid plate.  Since the coverage is complete by the skid plate, I could not determine where the oil leak was coming from for sure, but it appeared to be from the crank case vent tube.  Just prior to leaving for home, I checked the oil level and it was about 3-4mm below the ‘low’ mark on the dip stick.  Not good when there is only 34oz. in total.

Anyway, I spent Saturday night cleaning all of the oil off of the bike and giving her an oil change to ensure the correct amount.  Sunday morning I fired up the bike and ran it through several heat cycles at variuous speeds and throttle positions.  Nothing.  Nada.  No oil leak anywhere.

Later in the day I decided to check the coolant level.  It was full as of three rides (including Saturday) ago.  The capacity is about one quart.  I added half of a quart to bring it back to full.  UGH.  I think the problem was now identified.

The running like crap and spark knock are symptoms of extreme heat no doubt.  That is good in helping me determine if I have a problem.  But I am stumped in that I can’t figure out what would cause the crank case to be pressurized enough to dump oil out of the crank case vent tube. 

But as for now, the Yamaha has not in fact let me down.  Rather, I almost let it down due to my neglect.  I check the oil before every ride as well as the tire pressure.  The visual on the coolant is way too easy not to do so it will be checked every ride from now on.

Regardless, the bike ran great all day today without a drop of oil.  The plan is to ride next weekend with some extra oil just in case.  Oh, and I also don’t plan on veering too far off of trails that  a truck can reach.