More information on the dirty oil
I checked compression today and got 190 psi, using my roller starters with the bike in 1st gear. I then checked my B50 roadracer, which I rebuilt several years ago. Its compression was 210 psi. The roadracer is standard bore and stroke, 84.5 x 90, while the landspeed bike is 92 x 75. Both use a Megacycle X4 camshaft. The Landspeed bike cam is retarded about 2-1/2 degrees, and has higher lift rockers (about 10% more lift). Compression ratio on the roadracer is about 12.5/1, while the landspeed bike is about 13.25/1.
Would the lower compression reading of the landspeed motor be significant in this case?
Chris (Milwaukee Midget) sent my a personal message and I responded to his questions with this:
"Chris,
For the dyno runs, I was using last years BUB Speed Trials 110K which had been stored in a closed plastic container. For the Loring event, I used event gas, but it was a new vendor and I don't know what their designation was. It was supposed to be equivalent to VP's C-12.
I don't have the equipment to do a leak-down test, but I just did a compression test which yielded 190 psi (about 10 compression cycles, bike in 1st gear, roller starter on rear wheel)
As for crankcase vacuum, I got 12-13 inches of H2O when running the motor at rest with no load. I don't know what I was getting during the runs, but I did see oil drips from the exhaust pipe after the runs, and had oil in the reed valve when I took it apart.
There is another possibility. I had of course drained my oil when I pulled the bike apart last winter and drained the oil tank as well. I usually blow the oil out of the oil tank by pressurizing the vent hose, which forces the oil out of the tank very quickly. I say usually; it's possible that I just let it run out on its own last winter, but not likely as it takes about 15 minutes to empty that way. On the possibility that I didn't blow it out then, I did blow it out this time. It's therefore possible that I blew out some sludge that had settled in the oil tank, got shook up, and then got blown out yesterday."
Regardless, I'll run at BUB speed trials and change the oil after a few runs to check it.
Tom