"BenC" wrote in message
om...
"Mr Wizzard" wrote in message
news:f2Fed.415363$mD.411619@attbi_s02...
Got an old Monkey Wards Sea King .7.5 by Chrysler, and I am stumped.
It won't run on the bottom cylinder, not matter what I do. So far, I've
:

changed the head, head gasket, coil, converted to electronic ignition,
went over the carb (twice), two new sets of plugs, looked at the reed
valves, and it STILL won't run regularly on that bottom cylinder. Runs
fine on the top cylinder, and every now and then you hear I occasionally
hear it pop and shutter, and hear it kick in, but for the most part, the
bottom cylinder won't run. Plug just black, sometime fluffy black,
sometime wet black. I even looked at the fuel pump diaphragm
under a magnifier glass, and it too looks fine. So what the heck
could I be missing here? Compression is at 150 Lbs. I just don't
get it. The only thing I can think of is the bottom crankcase seal
is bad, and I'm sucking in air or water or something. I even took
off the exhaust manifold plate to make sure the exhaust port wasn't
plugged. Peeked in the exhaust port, and the edge of the piston
looks fine. Surely someone have the missing clue, help!!

Thanks !


it sounds very much like a bad bottom crank seal. if you have good
spark and good compression and the carb is clean you are only left
with bad reeds or bad crankcase sealing. can you still buy parts for
that bad boy?

Ah, thats what I was afraid of. So lets talk about this - you seem to
seasoned, and knowledgable about this. Compression *is* good,
yeah. As I said, I questioned water leak at water jacket, so I went
and got a good used head, wet-sanded it on a 1/4" sheet of coffee
table glass, got that baby "aircraft grade" FLAT, torqued the head
and new head gasket to 70 in-lbs first, then same pattern at 130 in/lbs.
"some" (limited parts) are available. So.... This bottom crank seal....
What exactally do you suspect is happening? Water/air getting "in",
or fuel charge getting "out" ?? An d the reed valves..., they seem
perfect (accourding to how the service manual says to check them).
Service manual says MAX .005 in "lift" (distance the pedals are up
from the reed box). This engine has 2 pedals for each cylinder,
and on the bad hole, they were well within the limits. I would think
that for reeds to be causing this, they would REALLY have to be
obvious miss allignment, damage to the reeds for this cylinder, right?
So I come back to either the bottom seal, "or" still some oddaty
with the carb. Since any liquid coming out of the carb would fall
rignt down into the crankcase for the bottom cylinder by virtue of
the physical design of the reed box etc. So I'm wondering, is it
possible that raw fuel spray is hitting the reed box, and the liquid
part goes downstairs, while the upstairs takes the nice vaporized
part of the fuel mixture ? Or am I reading too much into that?
One part of me says that if the mixure was *that* rich/wet (due
to some unseen carb problem), then the top cylinder would'nt
be running as well as it does. (and it does run amazingly well).
Its just that sometime wet, black wet, fluffy-black, and combo
(like its running way too rich). But you'd get that over time on
a cylinder that wasn't firing, or able to maintain combustion. So
how common is the bottom crank seal to fail? Failure mode ?

many many thanks! - I'm totally fustrated here.