Compression Test 2001 XR650


6 replies to this topic
  • ghride

Posted January 21, 2007 - 10:29 PM

#1

Anyone know what a good compression test reading would be for a 2001 650.
Due dilegence on a used bike with well maintained bike with a few hours on it.
I found a site that said a minimum of 100psi. How does the compression ratio 10:1 vs 11:1 translate into fresh psi? Any insight appreciated.

  • johnnyonthegas

Posted January 21, 2007 - 11:03 PM

#2

R or L?....sounds like an R....

  • cleonard

Posted January 22, 2007 - 12:07 AM

#3

Anyone know what a good compression test reading would be for a 2001 650.
Due dilegence on a used bike with well maintained bike with a few hours on it.
I found a site that said a minimum of 100psi. How does the compression ratio 10:1 vs 11:1 translate into fresh psi? Any insight appreciated.


The problem is the decompresser. It keeps an exhaust valve open, so you don't see full compression.

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  • ghride

Posted January 22, 2007 - 09:34 PM

#4

Its a 650R.
I asked the local Honda dealer and the mechanic said a fresh rebuild would give 86 psi with decompressor engaged and 160 psi with decompressor lever released. So my next query is whats the cutoff pressure to be concerned, 120? 140?

  • cleonard

Posted January 22, 2007 - 11:14 PM

#5

Its a 650R.
I asked the local Honda dealer and the mechanic said a fresh rebuild would give 86 psi with decompressor engaged and 160 psi with decompressor lever released. So my next query is whats the cutoff pressure to be concerned, 120? 140?


I always thought that with the kick starter, you couldn't turn if fast enough to disengage the cam decompression system.

What are you measuring?

  • ghride

Posted January 23, 2007 - 01:24 PM

#6

I havent tested it yet, I'll be test riding the bike and compression testing this weekend.

You may be right, I dont know that much about how the decompression system works, I presumed that if you dont - pull and hold - the decompression lever than you would be kicking against full compression, which is consistent with the 2 different PSI's noted from the honda dealer.
Guess I'll have to check it and find out.

  • ghride

Posted January 23, 2007 - 04:35 PM

#7

cleonard,
do you know for sure if the 01 XR650R has an auto-decompression system that disengages once the rpms get high enough?
After reading a few other related posts, I started learn what you were referring to. The 160 psi the dealer mechanic gave me may be when the auto-decompressor is deactived somehow.
A motion pro leak down tester is a little spendy for my needs right now, I could put new valves in for the cost of one.





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