REFLECTOR: Engine troubles

Geoff Gerhardt geoff.gerhardt at gmail.com
Wed Mar 7 20:05:58 CST 2012


Mike: I did it both warm and cold earlier in the week with a different
compression tester and got similar results.  Today, I did it cold with an
aviation-spec compression tester.  While I agree that slightly different
numbers could be had cold/warm - these are terrible numbers.

John: Yes, I agree - I can't understand how they could all be bad.  I took
the valve cover off #1 just to check that at TDC, the lifter was not
holding the valve up - there was a bit of play in the rocker indicating
that both the intake and exhaust valves should have been fully seated and
no force was being put on them by the lifters.

Geoff

On Wed, Mar 7, 2012 at 8:57 PM, Mike Dawson <medawson250 at yahoo.com> wrote:

> It is my understanding that you never perform a compression check on a
> cold motor.
> Make sure it is hot. Then try it.
>
> Michael E Dawson
> ATCI CFII
>
>
> On Mar 7, 2012, at 5:32 PM, Geoff Gerhardt <geoff at thegerhardts.com> wrote:
>
> > Some of you might remember a few weeks ago, after taking my first taxi I
> did a full run up and found my static was low.  After doing some
> troubleshooting, I found a couple issues - an intake leak and a faulty
> electronic ignition box.  My Light Speed ignition box is off to Klaus at
> Light Speed Engineering to be fixed.
> >
> > During the process of checking the timing/ignition, I noticed that when
> I was trying to find #1 TDC by putting my thumb over the spark plug hole to
> check when it was on a compression stroke, I was not feeling much pressure.
>  So, I recently did a compression check.  The numbers were dismal. All were
> low: #1 - 10/80, #2 - 20/80, #3 - 24/80, #4 - 10/80.  All were leaking
> copiously past the intake valve.  Exhaust valves sounded tight, some
> leakage could be heard past the rings.  I took the intake pipe off #1 and
> put my fingers behind the valve and could feel the air rushing past.  Not
> sure why its so bad.  Looks like the guy who sold it to me (an A&P and
> Velocity owner) is either a terrible A&P or dishonest.
> >
> > Can someone tell me my options?  My preference would be to rebuild it
> myself (I've rebuilt many engines, most recently a Porsche 911 - pretty
> similar!), so I'd look forward to it.  The drawback of that is time.  I
> could probably tear it down in day, but I suspect sending stuff out for
> inspection and acquiring all the necessary parts might take awhile.  What
> are my options for the cylinders?  Send the out for rebuild?  New?  How
> much $ are we talking?
> >
> > The other option would be to send it to a rebuilder - definitely be more
> expensive, but do they have relatively quick turn around times?
> >
> > Geoff
> >
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