valves and compression Question

5 replies to this topic
  • Bamster

Posted August 05, 2002 - 04:57 AM


Will tight valves cause any compression loss?
I have rebuilt 2 strokes in the past but I'm pretty much a bone head when it comes to thumpers.I am learning.
I noticed that I can push the kicker through
top dead center slowly(with difficulty and all my wieght on the kicker)on my 99 WR 400.Is this normal ? Could it be tight valves or is it in need of rings?Thanks

  • freestyle111

Posted August 05, 2002 - 05:39 AM


yes, tight valves could cause loss of compression.valves that are too tight will not close and seat properly.valves that are too loose wont open all the should either take valve cover off and check to see if valves are with limits or you can do leakdown test which should tell you whether its rings,intake valves,exhaust valves.

  • Bamster

Posted August 05, 2002 - 06:08 AM


If I do a leakdown test, how will I know if its
rings or valves? Or will I just have to do the process of elimination ? Starting with valves
and moving to rings.
If the valves are tight do they make any noise?

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  • Woodzi

Posted August 05, 2002 - 08:11 AM


Sounds like you are OK if it takes all your weight to move the kickstarter past TDC. (don't do this or you will break something) You should check the valve clearances first. It is easy, and even if the valves are not tight they could still be out of spec. If you do a leak down test and the results are bad, repeat the test with some oil in the cylinder (just enough to coat it). If it is still bad the problem is with the valves. If it is OK with the oil, then the rings are bad.

  • freestyle111

Posted August 05, 2002 - 09:46 PM


if your intake valves are too tight or not seated properly you will hear air passing thru carb into airbox,if exhaust valves are problems the air will go out thru your exhaust you will feel air if you put hand over end of silencer while testing.if its your rings air will be coming out oil fill tube on frame.isf you search internet for "leakdown tester" you will find detailed instructionals and how to diagnose problems.

  • Bamster

Posted August 06, 2002 - 05:00 AM


Thanks guys,The imformation provided was very helpful.
Hey Woodzi are you going on the Calibogie ride?
I'm going to try to be there. 4 of my friends
are going for sure.


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