WR400 compression help please!


2 replies to this topic
  • -chris-

Posted April 20, 2008 - 05:16 AM

#1

Hi everyone, I've searched this forum and nothing seems to relate exactly to my problem....
I fell off yesterday after hitting a tree pretty hard and the bike started up again after a few kicks, minutes later it was losing power and finaly stalled. As on other posts the kickstart can be pushed with your hand without the decomp (which does not appear to be stuck on).

With the choke on and the throttle wide open it did just start and tick over but stalls after a few seconds. Not tried this again for fear of damage but I did notice air flowing from the breather pipe while running. I'm guessing valve problems but any advice or ideas would be appreciated.

I have pulled the seat, tank and cam cover off this morning but thats as far as i've got so far.

Thanks in advance.

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  • Frostbite

Posted April 20, 2008 - 06:54 AM

#2

Hi everyone, I've searched this forum and nothing seems to relate exactly to my problem....
I fell off yesterday after hitting a tree pretty hard and the bike started up again after a few kicks, minutes later it was losing power and finaly stalled. As on other posts the kickstart can be pushed with your hand without the decomp (which does not appear to be stuck on).

With the choke on and the throttle wide open it did just start and tick over but stalls after a few seconds. Not tried this again for fear of damage but I did notice air flowing from the breather pipe while running. I'm guessing valve problems but any advice or ideas would be appreciated.

I have pulled the seat, tank and cam cover off this morning but thats as far as i've got so far.

Thanks in advance.


My first guess is that you pinched or dislodged/damaged your decomp cable or lever when you crashed. If it spun a bit on the handlebar, it could make the cable effectively "shorter". Since the bike started normally I don't think you damaged the engine enough to cause a loss of compression. I'd say the cable is kinked or pinched, and the first time you turned hard to the left, the cable actuated the decomp causing a loss of compression and eventually stalling the engine.

I had this happen to me after a tumble. I got back up and refired, but the engine stalled when I turned the bars to the left. The decomp lever had spun, pulling on the cable, and turning to the left had the same effect as pulling the lever.

I'm guessing the cable is jammed because it should release back. If your cable is pinched or jammed, the small return spring wouldn't be strong enough to reset the decomp back to the off position.

Look at the head where the decomp arm actually is, and manually turn it to the "decomp off" position, to make sure that it is completely dis-engaged. Then see how your compression is. If compression returns, check the cable.

  • -chris-

Posted April 20, 2008 - 10:41 AM

#3

Thanks frostbite but it seems my hunch was right, take a look at these cams..

Posted Image

Posted Image

Sorry about the photo quality...




 
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