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advice in this forum.]----
Longshot, but maybe the cylinder isn't getting enough fuel to it. In a carb
engine, I wouldn't have the slightest idea but to think that an intake
manifold gasket is to blame. If there's a leak it'll run too lean. Another
pbm may be the intake valve itself. Top or bottom plug? Also, suspect the
lifter. Did you change oil types or weights? Check the hole at the plug
for cracks.
When you say "hot" cylinder, do you mean the problem child or that the
cylinder is running hotter than the others?
Al
----- Original Message -----
From: <[EMAIL PROTECTED]>
To: <[email protected]>
Sent: Wednesday, August 30, 2006 5:10 PM
Subject: [COUPERS-TECH] Continuing Problem
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advice in this forum.]----
A mechanic and I are out of ideas trying to solve a three week old problem
on the 85HP (converted from 75HP) engine on my 1946 415C, N2738H. Any
advice and help anyone can give us would be greatly appreciated.
The problem surfaced at run up with a 200RPM drop on the right mag. This
was after 25 hours (about 25 flights with no problems of any kind) Left
mag was normal with about 25-50 RPM drop. The right mag had 25 hours on
it, the wiring harness and all 8 plugs had 25 hours. So far we have done
the following:
1. We bought a rebuilt right mag from Aircraft Spruce to replace the one
with 25 hours. Installed the new mag with no change; still a 200, or
more, RPM drop on the right mag. Even had minor backfiring. We bypassed
both key and p-leads with no change, still a 200 RPM drop on the right
mag. Then we reversed the mags with no change, still the 200 RPM drop on
the right mag. We concluded at this point that it was not a mag problem.
2. We installed 8 new plugs to replace the plugs that had 25 hours on
them. No change, still a 200RPM drop on right mag.
3. About this time we ran the engine on the right mag long enough to
identify the cold cylinder, #4.
4. We installed a new wiring harness to replace the 25hour harness. No
change, still the same, or worse, RPM drop on the right mag and #4 was
still cold.
5. We then again loosened the front cowling and removed the metal cover
from the #4 cylinder plug and directly wired the wire to the plug without
using the plug cover. This engine still has the small plugs on top. No
change, still the excessive RPM drop on the right mag.
6. At this point we think we have eliminated as the problem the mags, the
plugs, the wiring harness, the covers on the top plugs., the P-leads and
the key system. And the engine/mags have been timed several times with
the left mag showing no problem and the right mag continuing to show the
excessive RPM drop, so we think we have eliminated timing as the problem.
We also think that a problem internal to cylinder #4 would affect both
mags and not just the right one.
We have run out of ideas and really need your help. Any
ideas/possibilities would be greatly appreciated. Thanks, Dennis Hatfield
N2738H.
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