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1980 550e with no compression

  • Thread starter Thread starter iAlex
  • Start date Start date
I

iAlex

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I just completed a top end rebuild and now I can't get the engine to start. A compression test on cylinders 1 and 4 was only giving me about 40 psi. Unfortunatly I was pressed for time and was unable to test 2 and 3. I checked the valve timing and it looks to be dead on. I do have one question though. Am I supposed to time the valves with 1 and 4 at TDC or am I supposed to time it for 2 and 3 at TDC. The Clymer manual is a little bit vauge about this but according to the picture I am supposed to time the valves with 1 and 4 at TDC. In my view the valve timing is the smoking gun but I'm not 100% sure. Could the low compression be a result of the head gasket or the piston rings? Any help is appreciated. Thanks,

Alex
 
Agreed, your timing is off letting compression through the valves.
 
I left the valve clearances to what they were when I disassembled the bike. I timed the cams with pistons 1&4 at TDC and set the exhaust cam with the 1 arrow pointint slightly below the gasket surface. Then I went 20 rivets on the cam chain from the number 2 arrow on the exhaust cam to the number 3 arrow on the intake cam. Then I installed the tensioner and checked the timing one more time.

When I was putting the engine back together I didn't replace the piston rings. Could this be a source of my problems? If so then where is a good source for piston rings? Thanks,

Alex
 
Here are some pictures of my cam timing as it currently stands.

TDC.jpg is the cam position when 1&4 are at TDC.
 
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And then this picture is when the cam is lined up exactly with the gasket surface. This position corresponds with the Fire mark on the crankshaft.

I'm not sure how to get the cam lined up exactly with the gasket at TDC. To me it seemls like it will either be too far below the gasket or to far above the gasket due to where the sprockets and the cam chain fit together.

Any thoughts?
 
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Now to make the story even stranger. I moved the cams one link back on the timing chain. Cylinder 4 gives me 100 psi for the compression test. Cylinder 1 and 3 give zero. I didn't check number 2. Needless to say I am baffled as to what is causing this problem now.

Alex
 
Since I hate it when I look through old post threads and never find out how a problem was resolved I figured I would post what I found with my bike.

I was able to finally get the motorcycle running again. To start out after I was having the cam timing issues I put oil in the cylinders and was able to bring the compression on some of the pistons up to about 40 PSI. So I figure that my rings were causing the compression problem. So I took the engine competly apart again and replaced the piston rings with new ones bought from Bike Bandit. I gave the cylinders a fresh crosshatch with a cylinder hone and put the bike back together. This time I was able to get about 40 psi on all 4 pistons. Frustrating to say the least. I checked the cam timing again and it was spot on. Finally it dawned on me to check the valve clearances. The intake clearances were way too large on all 4 cylinders and the exhaust clearances were too tight. I'm sure that at one point during the first assembly attempt I mixed up which valve buckets were which and put all the exhaust buckets on the intake side and vice-versa. So now I changed the shims from the exhaust to the intake and moved the shims from the intake to the exhaust. A quick compression check of #4 gave me 125 psi. So I put the bike competly back together, gave it a shot of starter fluid, and was able to finally start the bike after 5 months of having it apart on my garage floor.
 
Hey, thanks for posting the solution. I too hate it when you never find out what fixes the problem.
 
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