Webra 1.60 problem

[Ed Alt]

I ran into a little snag while starting a fairly new Webra 1.60 today. It has about 30 flights and has been running well, with the exception of the previous two flights where it suddenly didn't want to stay lit after starting, just prior to takeoff.  Trouble free during those two flights though, this with a replacement OS type F plug just in case.

Back to the problem today, while starting, there was suddenly a great deal of binding while turning the prop.  I pulled the prop and discovered that the thrust washer was scraping against the crankcase and had produced a couple of fine shavings.  Also noticed the dreaded metal/grease paste from previous wearing, all around the end of the case and behind the thrust washer.  

I don't think any shavings got into the front bearing, since it never ran once I noticed the binding, but it's a fairly sure bet that this has been making some contact when the starter has previously been in use, so some amount of crud has probably passed through.  Compression is still great and there is no visible sign of wear to the liner or piston, so my first question is about whether to tear it all down to clean it and replace bearings just in case.  The second and more pressing question is why did this happen in the first place?  Is it possible that over tightening the prop nut will force the thrust washer far enough back to allow contact under the load of a starter?  Is it more likely that there is a main bearnig wear problem allowing the contact?  There is very little run out to the crank when pushed/pulled from the front, but should there be any that is detectable this way?
Thanks
Ed
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://lists.f3a.us/pipermail/nsrca-discussion/attachments/20040620/c5a4ddcb/attachment.html