Reeds causing low compression reading???

[moto45]

Hello, I'm new to the forum and of course I've got a question. I'm working on a 1983 CR125 and keep getting low compression readings ~120. I've read through the treads relating to reeds and low compression and have not found an answer to this question. Can worn or frayed reeds cause a low compression reading?

Yes, I held the throttle open while doing the test. I've redone top ends before and have pretty good command of the basics. The cylinder specs. out and have new rings and gaskets. All bolts torqued to spec.

Readings were not lower when reeds were totally removed. I've got new reeds on the way but in anyone has insight I'd love to hear it. Thanks in advance.

 

[RM_guy]

Reeds don't affect the compression but frayed ones will affect low end and starting. Did you break in the new top end before measuring the compression? If not then break it in and try it again once the rings are seated.

BTW, welcome to DRN :)

 

[moto45]

Reeds don't affect the compression but frayed ones will affect low end and starting. Did you break in the new top end before measuring the compression? If not then break it in and try it again once the rings are seated.

BTW, welcome to DRN :)

Thanks, well to answer your question, no I didn't do the compression test after the rings were seated due to the fact that I was having a hell of a time getting it started. Once again, this leads me back to the reeds.

Hopefully, I'll know more in a couple of days when I get the reeds in. One note, the rings that I replaced were well within spec. and may not have needed to be replaced. I did it more to eliminate one of the possible casues. Which leads me to think that they were not the problem.

 

[chillrich]

I have asked a similar question to a local machanic at one of our bike shops. In my case the reed block gasket was suspected to be faulty and compression was ~90. The machanics answer was that this does not affect compression. When I lloked into it I could see why, the Intake feeds into the crankcase first and then gets scavenged into the cylinder on the second stroke. I believe that the reeds will affect the leakdown test.

Hope this helps.