Subject: RE: Valves & related fun, '71 Ambo
Author: joe jump
Date: Sep 12, 2003, 9:22 AM
Post ID: 1714497536
Sean,
Don't rely on the temp of your valve cover to troubleshoot
leaky valves. Bad valves don't allow exhaust gasses under your valve
covers. Go ahead & invest in a compression tester. Remember to hold the
throttle WFO while doing the test. Don't be too concerned about the
gross readings-it's the difference between the two that matters most. A
leakdown test, using a compressed air source to pressurize the
combustion chamber (at TDC comp. stroke) will give a better diagnosis of
valve/ring leakage. Make sure your valves are adjusted correctly (again,
at TDC comp. stroke) prior to condemming your valves.
To pull a cylinder head will require a spanner wrench for the
header nut and a 10mm allen wrench/socket to remove the nut on the
cyl-to-head stud located at the 12-o-clock position. The rest is all
pretty much straight forward. Any standard valve spring compressor, or
even some imaginative use of a big C-clamp will compress the spring
enough to remove the collets.
You may be able to resurface your valves/seats vice
replacement-much cheaper. Cheaper yet, you may be able to lap them in
using a lapping tool (suction cup on a stick) & some lapping
compound-depends on how bad the valves/seats look. If you need a
machinist to help you, be careful who you take your parts to. I've seen
some real butcher jobs done that render the parts useless. Try to find
somebody with motorcycle experience & a good reputation.
But do some more careful checks prior to tearing it down-it
might be just a simple adjustment required to get it runing right.
Sean Flanagan wrote:
Hello all and TGIF- In the recent past I've made some inquiries here and received piles of help for getting my '71 Ambo back in running order. Thanks again for all of the assistance so far! It's been fun & educational, to say the least. After getting the timing nailed down last night, I took her for her longest run yet, a few miles down the road & back. Doesn't run well, but she runs! Back in the garage, I noticed that the right cylinder cover was hot, but touchable, the left cylinder cover was sizzle-your-skin hot! So I thought, bad valve(s), letting hot combusted gasses in there and generally cooking it. Also did a "workingman's leakdown test", kept the plug in and turned the crankshaft via the bolt on the front. At TDC I could definitely hear air coming out with a Pffft! sound, and I'm fairly sure it was the intake side. But at this point I'm willing to do both valves on that side. Anyway, long story long, I want to replace the valves. This is the 1st time I've ever done this, so I'm not sure what sort of tool I need to compress the valve spring. And of course, your experiences & advice this area would be greatly appreciated. Thanks in advance Sean in Flagstaff, AZ, USA |
Joe in St Louis