This write-up is about how I found crankcase pressure within the bottom of my '05 TRX450R engine.
The very first indication that my bike had an issue was when my "butt-dyno" felt that something was a little off. It felt like the bike was falling flat on its face in the upper RPMs. I thought the issue might be jetting, so I swapped brass for several weekends to try and cure the problem...all to no avail.
Next, I took my bike to Precision Motorsport's Mobile Dyno in Culpeper, VA to see if the dyno tuner could find the correct jets to fix the problem. After trying several different jets, I ended up leaving the dyno with a seemingly incurable dip in power starting at around 7500 RPM. This was the second indication of the real problem. The dyno graph below is one from this dyno session. You can see the full results of the dyno session here.
After this, I knew the problem was not jetting related. So, with the help of my Dad, I began checking everything that I could personally check to try and find where the issue was:
During these checks, I found the third indication of the real problem. After removing the exhaust system from the bike, I found an oily film sitting in the exhaust port that was still sticky from the ride I had taken early in the day. I thought maybe the piston rings were worn since the piston had a 2-ring design and had been in the bike for over a year. The bike did not smoke at all though, which was odd; but I dismissed the finding prematurely concluding that the rings were worn causing the bike to burn some oil.
After everything in the list above checked out o-k, I began swapping parts to see if anything made a difference in power in the upper RPM range:
After the part swaps did not make a difference, I personally, could not go into the engine any further. I'm a computer nerd, not an experienced mechanic. Thoroughly checking for all of those problems and swapping all of those parts took months of time. I stayed on campus at a university 1.5 hours away from home taking 9 credit hours of classes and working 40+ hours/week at this time. I would come home on Friday nights and start working on the bike pretty much non-stop (just to eat and sleep) and finish up on Sunday afternoon just before heading back to school.
After many months of trying to find the problem myself, Wicked Motors in Maryland agreed to take my bike to see if he could find and fix the issue. He swapped everything on the top-end to try and fix the problem:
During this time Wicked Motors was able to put my bike on a superflow dyno. Once on the dyno, and with a load on the engine, the bike sounded sick and made a strange gurgling noise down inside in the crankcase. Another tear-down revealed that if he took the cam chain off the cam gear, and turned the engine over by hand, using his finger as the "cam gear," his hand would be soaked with oil in just a few seconds. There was something pushing the oil up from the bottom end. He dove into the bottom end and found the problem.
The first two pictures above are of the relief valve in the oiling system. If the oil cooler gets some blockage, it forces the relief valve to open and returns the oil directly back to the crankcase. You can see the black piece of material to the left of the spring in the third picture above...this piece was in the relief valve holding it open, bypassing the oil cooler and dumping the oil directly back into the crankcase. The piece of material looked to be a plastic piece off of the timing chain guide or tensioner....possibly an imperfect chain guide mold...a piece that chipped off and eventually found its way into the relief valve. This explained the flat spot in the upper RPM's, the dip in the dyno curve, the residue in the exhaust port, the gurgling sound from the crank case, and the oil soaked cam chain.
After the relief valve was unplugged, the oil level in the bike dropped a 1/2 quart. After the engine oil was topped off, and the bike was taken for a ride, it had been cured. No more oily film in the exhaust port, no more gurgling, and it no longer sounded sick. The bike finally ran well. And, after taking the bike back to the dyno, the power curve looked great with no dip in the upper RPM's. You can see the full results of the dyno session here.
Thanks again to all of those involved in helping to find and fix this problem!