- Nov 20, 2008
After fitting some pistons I had around here with new gapless rings and discovering the top lands were very close to the wrist pins which resulted in a 1/4"distance from the top of the piston to the top of the barrels at TDC, I thought it should give the old Norton an easy long life with such low compression. I has also installed a special crank seal from the aviation industry which had 6 fine contact surfaces instead of the usual 1 where the circular seal presses the rubber into the crank shaft. I was told it would be leak proof. However what I didn't anticipate was the increase in crank case pressure on the other side of the pistons as this inadvertently increased the compression rate below the pistons. Aside from lacking much power I noticed oil everywhere and oil tank farts when shutting down. The chaincase oil had bits of metal and was black from the ground down rubber of the seal. The seal was pushed clear into the engine sprocket where it was ground to nothing.