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Valves began leaking after head reinstall

  • Thread starter Thread starter Tesla
  • Start date Start date
T

Tesla

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I previously had a bent valve in one of my cylinders. I opened the engine up and replaced it. The other valves were leaking a small amount so I went ahead and lapped all of them. Before going into the engine I tested the compression and got 130s, 130s, 30s, 130s respectively for cylinders 1,2,3,4. This seems to be telling me that the other three cylinders nothing is wrong with. After reinstalling the head I tested the compression again and I got 80,85,90,50 on the compression. Before reinstalling, I tested the seal of the valves by putting some marvel mystery oil into the head to see if it leaked. After leaving it overnight almost no oil leaked through making me believe the valves were correctly seated. there was some residue oil around the seal that I can hear bubbling up on the intake valves showing that somehow now after reinstalling the head the valves are no longer seating right. All of this is being done cold. Currently compression tests are being done by running the starter engine without carbs or exhaust connected.

Any Ideas? This is the first experience I have had with engines and I was really hoping that it would work after fixing the bent valve. Apparently I have done something wrong when reinstalling.

Thanks in advance for the help
 
Did you properly set the valve lash? And of course we have no clue what kind of bike you have.
 
Compression test should be done when the engine is at working temperature with throttle wide open.
your results on 3 cylinders are not bad for cold readings but the 50 psi cylinder is way off is this the one that had the bent valve?
if the valve lapping has been done correctly there should have been no seep of the test fluid.
have you rechecked your valve clearances?
 
fastbysuzuki said:
Compression test should be done when the engine is at working temperature with throttle wide open.
your results on 3 cylinders are not bad for cold readings but the 50 psi cylinder is way off is this the one that had the bent valve?
if the valve lapping has been done correctly there should have been no seep of the test fluid.
have you rechecked your valve clearances?
Click to expand...

With no carbs attached, the throttle position is irrelevant. ;)

Even cold, the 80,85,90 numbers are a little anemic. Do as others have stated. Start by verifying your valve adjustments.
 
Many times it is necessary to check compression cold, often when buying a non-running bike. If it has set a long time, readings can be misleading until the rings start sealing a bit but as has been noted, less than 100 cold is not good. Since you are having a compression issue and the head was redone, you should do a leakdown test using a gizmo like this:

http://www.ebay.com/itm/151577667842?_trksid=p2057872.m2749.l2649&ssPageName=STRK:MEBIDX:IT

I have one and it works well enough to tell you where any compression issues lie. Suggest you mention what valve clearances you now have and if they were not checked, that would also be a good place to start diagnosing the problem.
 
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I have a sneaking suspicion it is the shims. the fluid is some excess oil from when I installed them. I did not actually adjust the shims. I also believe I put the buckets (spring cover things with the shims on them. not exactly sure what they are called) on different cylinders then they came off of...(just the buckets though. I made sure the springs were correct between intake/exhaust) Stupid I know but it is what I did at the time. I ordered a feeler gauge the other day and it will be in tomorrow so I will go ahead and check the clearances. I will post results and try to figure it out.

This forum has been amazing. Thank you everybody for all of your help
 
Tesla said:
Also for reference, what would be a good cold reading?
Click to expand...

It varies, but 90 is good.

I'm assuming your motor was running sometime recently?

You should check out the Shim Club, he's probably close to you, for new shim sizes
Be sure you do not rotate the cams without shims in the buckets!!!!
 
No hasn't been run in years. I definitely will not run without any shims at all. I pretty sure something is currently wrong so I don't really want to hook it up to the bike for a hot test. Ok I'll shoot for the 90-100 range. I'm going to pull the head cover tomorrow. Thanks again for the input
 
"I definitely will not run without any shims at all."

don't even rotate engine by hand without shims as cam lobes will do unpleasant things to shimless buckets
 
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