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jkuehn(at)mountaintime.my
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 Posted: Tue Jun 20, 2006 8:03 am Post subject: Cylinders too cool? |
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I have a 912ul in a tractor configuration (Sky Ranger) with just over 60
hours. The spark plugs in the front cylinders are darker and dirtier
than the rear ones. The electrode itself on the four front plugs look
normal; brown and clean. But the rest of the plug is covered with a
thin layer of carbon that I do not find on any of the rear plugs. I
think this is because the front cylinders run cooler than the rear ones,
and I am wondering if this is OK. Should I be cowling those front
cylinders? I have seen pictures of a plastic cover on the cylinders but
have never seen this installed. Any thoughts?
Jack
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Thom Riddle
Joined: 10 Jan 2006
Posts: 1597
Location: Buffalo, NY, USA (9G0)
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| Posted: Wed Jun 21, 2006 3:33 am Post subject: Cylinders too cool? |
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Jack,
You may have seen my post earlier about sooty appearance of only
one(#1) forward cylinder plugs.
Yesterday, we finally got around to removing the right side carb,
disassembling, inspecting, and cleaning it. The only anomaly we found
was the "starter" jet was not screwed in snugly. This is the jet that
allows fuel to bypass the normal running circuits during startup using
the enricher. I think this may have allowed raw fuel to leak into the
manifold, even when the enricher was off.
One might wonder why this would affect only the front cylinder. Look at
the intake manifold from the top and you will see why this is possible.
Raw fuel can be carried in the high velocity air stream past the
Y-junction such that the raw fuel is present only in the forward
cylinder. What tipped me off to this was when we removed both intake
manifolds and saw a dark streak of dried excess fuel on the bottom of
the forward intake manifold only on #1 cylinder. You don't have to
remove the carbs or linkages to check this. I suggest you remove the
four bolts holding the intake manifolds onto the heads and look inside
the outlets of each tube. If you see this dark residue only on the
bottom of the forward tubes, you are probably having a problem similar
to mine. If so, next step is to remove, inspect, clean the carburetors
per instructions in Rotax Heavy Maintenance Manual. It is not hard to
do.
I'm not sure if ours is fixed yet because we can't run the engine until
we get a new exhaust system to replace our broken one. I'll post the
results as soon as available.
Thom in Buffalo
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_________________
Thom Riddle
Buffalo, NY (9G0)
Don't worry about old age... it doesn't last very long.
- Anonymous |
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