Monday, May 10, 2010 [19326 miles]
Last week my GS needed a 6K service. That, plus grandson babysitting duties (he had his first sleep-over) kept me away from the R69S.
Left side a touch low
Valve covers off
This afternoon I’m pulling the heads, but first want to do some general diagnostics to guide my attention. A compression test showed the left cylinder a touch low (170 PSI vs the usual 175-180). The right cylinder was quite low at 150 PSI max. Time to pop the valve covers to check which side is at TDC for a leakdown check.
Left side: 50 = 100%
leakdown: oil filler loose
To simplify the math I feed 50 PSI into the cylinder at TDC with the Oil filler loose to allow any air that gets into the crankcase to escape. The left side measured 41, or a loss of 9… 2 * 9 = 18% leakdown loss. The source is obvious on this cylinder… I can feel air from the exhaust port. The right side was a different story… 56% leakdown into the crankcase. I first thought rings.
Pulling the heads
Rocker arm assembly and pushrod
Left piston head
Left cylinder head
Right piston head
Right cylinder head
Leaky gasket, again
Another leaky gasket. No, this is not the same one I changed 500 miles ago, that was on the left side. This side measured good at that time. There may have been two leaks. The worst was around a head bolt. This caused the greatest loss of compression that I first thought was going into the crankcase. The second possible leak was around the pushrod tube on the intake side.
Right cylinder
Left cylinde
Because I was curious I rotated the engine to BDC to take a look at the condition of the cylinders. No obvious damage. I put the engine back at TDC and draped some rags over the pistons for now.
Parts
That’s all for today. Next I’ll pull the cylinders. Both heads will go out for work. If nothing else the valves should be touched up and the gasket surfaces checked for flatness. Also, the exhaust side of the right head needs drilling or reaming the head bolt channels, again.