No Compression



13 replies to this topic
  • Scott

Posted March 10, 2001 - 11:01 AM

#1

What am I forgetting??

Long story short - I had to remove the head to get to a piece of metal that had broken off my carb slide. I found the piece and inspected the everything looking for damage done by this piece. There was no sign of any damage whatsoever. Not even a scratch anywhere.

So, I put on a new head gasket, aligned camshafts per the manual, put everything back together, and now I have NO compression.

Prior to the removal of the head, I DID have compression.

Any thoughts?

Thanks in advance!



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99WR,WR timing,throttle stop removed,Uni filter,E-Series pipe,carbon air box,Pro Tapers,lights removed,YZ tank,13 tooth sprocket

  • BULLDOG

Posted March 10, 2001 - 11:24 AM

#2

Was you piston at TDC? Did you remove you valves or valve guides? Did you mess with the decompression mechanism while you were inside? I would suggest starting from scratch to prevent any damage.

  • Scott

Posted March 10, 2001 - 11:35 AM

#3

Yes, I was at TDC. No, I did not touch the valves. No, I didn't touch the decompression mechanism inside.

Dumb question, but if the punchmarks on the cams are off a tooth, could this cause the problem? When installing the cams, I made sure that they we aligned correctly, but I've never done this kind of work before, so I may have been off a tooth..?? :)

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99WR,WR timing,throttle stop removed,Uni filter,E-Series pipe,carbon air box,Pro Tapers,lights removed,YZ tank,13 tooth sprocket

  • BULLDOG

Posted March 10, 2001 - 11:46 AM

#4

One tooth should not make a difference except in performance. Unless you were 180 degrees plus one tooth off on your cam. Take the head cover off and check both cams again. It may be that you put a cam on 180 degrees off. Go to off-road.com and compare your cams to the posted pics on the site.

  • Taffy

Posted March 10, 2001 - 12:09 PM

#5

bulldog is there.

put a long round nosed rod (one that can't scratch the piston) down the plug hole.in the first or second crank rotation that sees the piston at top dead centre (as high as the rod can be pushed) the mark will line up in the hole in your left cover hole.

the cams should look a bit "pissed with each other" with the inlet pointing at 2 o'clock & the exhaust looking at 10 o'clock.

Taffy

  • Scott

Posted March 10, 2001 - 12:15 PM

#6

I appreciate the suggestions, but I know I installed the cams just as the manual shows:
.E I E I.

The punch marks are even (maybe a touch above) with the surface of the head.

Could I have thrown a valve out of whack?

When the head was off, I held it upside down at one point to look for damage and a valve lifter (shiney aluminum cap) fell off. I simply put it back on.



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99WR,WR timing,throttle stop removed,Uni filter,E-Series pipe,carbon air box,Pro Tapers,lights removed,YZ tank,13 tooth sprocket

  • Dougie

Posted March 10, 2001 - 01:45 PM

#7

Scott, this is way beyond my limited knowledge. But I'd be willing to take you out for drinks to drown your sorrows and discuss RMs :)

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  • James_Dean

Posted March 10, 2001 - 02:00 PM

#8

Does your compression release still have slack in the cable?

  • Scott

Posted March 10, 2001 - 02:38 PM

#9

The cable from the compression lever is tight. There is a touch of play. (Appears normal)

Could the timing chain tensioner have anything to do with it??

Am I supposed to "release" the tension rod after I screw the assembly to the head?



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99WR,WR timing,throttle stop removed,Uni filter,E-Series pipe,carbon air box,Pro Tapers,lights removed,YZ tank,13 tooth sprocket

  • James_Dean

Posted March 10, 2001 - 04:55 PM

#10

If you don't release the tension rod the chain would have slack and could jump out of time and.... lose compression.

  • Taffy

Posted March 11, 2001 - 12:33 AM

#11

scott

please do my check.

Taffy

  • Scott

Posted March 11, 2001 - 06:49 AM

#12

Thanks Taffy, I'll try it and let you know. You've always pointed me in the right direction.

  • Sandracer_uk

Posted March 11, 2001 - 07:51 AM

#13

i had the exact same thing happen to mine,,, i stripped it down , put a new piston and rings in [ there was no need as it happens ] slapped everthing back together and bugger me,,, no compression.
i took the head cover off and one of the little valve caps [ dunno the right name ]under the cams,was sticking in its housing,,, which meant the valve wasnt closing properly.
i took it out gave it a good spray with wd40 fiddled with it [ dropped it a few times ] put it back in and made sure it wasnt catching ,,, all sorted out,,,,, sounds to me like this might be the case with yours too.
hope this helps

  • Scott

Posted March 14, 2001 - 12:25 PM

#14

I have compression! I pulled the head cover off and noticed that the cams were NOT in the same position they were when I last saw them. Apparently, the chain tensioner did not open as I thought it had and the chain had some slack in it. I think it jumped the cam..

Taffy,
I tried your test, but, unless I'm completely nuts, the TDC mark "I" only aligns when the piston is at the top. I never saw the "I" line up when the bamboo shoot I stuck in the spark plug hole was at the low position.

I know the chain tensioner is working now and I made sure that there were 13 pins in-between the top punch marks on the cams.

I also pulled off each valve cap and peeked around. I made sure the magnets were seated properly and then reinstalled.

So whatever I did/re-did seems to be working. It did start, but I have yet to ride it..

Thanks again to all who responded! I really appreciate it.

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99WR,WR timing,throttle stop removed,Uni filter,E-Series pipe,carbon air box,Pro Tapers,lights removed,YZ tank,13 tooth sprocket




 
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