Oil on spark plugs - Inverted 503

by Harvey Parent in 2 Stroke Technical Questions 13 years ago

I removed the spark plugs on my inverted 503 installation (Challenger II) and found oil had accumulated in the spark plugs filling half way up the insulator. The engine has 140 hours on it so I don't think it is a ring problem, but just oil seeping down from the crankcase over time. The plan is to leave an old set of plugs in between flights and put the good set in before flight. That much oil burning off of spark plugs that are left in would reduce plug life considerably. Any one else having this problem?

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Re: Oil on spark plugs - Inverted 503

by Roger Lee » 13 years ago

Roger Lee

125 5.11k 4.52k

Hi Harvey,

I take it that it runs okay after it is started and only happens if let sit for a long time?
If you have an inverted engine and it sets for long periods fluid can migrate down into the cylinders. Either fly more regularly or pull the plugs after a long sitting period and rotate the prop to clear some of this out.

Roger Lee
LSRM-A & Rotax Instructor & Rotax IRC
Tucson, AZ Ryan Airfield (KRYN)
520-349-7056 Cell

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Re: Oil on spark plugs - Inverted 503

by Harvey Parent » 13 years ago

Harvey Parent

1 8 0

Hi Roger,

I wish it would fly a lot more regularly, but unfortunately it's not flying as often as I would like. I will take your suggestion to rotate the prop with the plugs out to clear the cylinders.

Thanks,

hp

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Re: Oil on spark plugs - Inverted 503

by Nick Axworthy » 13 years ago

Nick Axworthy

16 325 0

Goes with the territory with inverted motors Harvey,

Have you tried to start it with the plugs as they are,

What makes you think running it with some oil in the plugs will shorten there life....I think I would be mre bothered taking the plugs out so often with the risk or thread erosion of the plug hole with them in and out so often.

But if it wont start well you would have no choice I suppose.

Nick.

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Re: Oil on spark plugs - Inverted 503

by Harvey Parent » 13 years ago

Harvey Parent

1 8 0

Hi Nick,

Thanks for your reply. Yes, I agree, plugs down will always be a problem. The engine starts OK, however, I suspect since the spark plugs fire in pairs (in series with each other) the plug that is first to accumulate more carbon will soon stop firing altogether. I am just trying to increase reliability of the ignition system by keeping the spark plugs as clean as possible during the expected 25 hours of service.
The plug threads will have anti-seize compound applied and torqued to specs to reduce wear on the cylinder head spark plug ports.

I wonder if most users are getting 25 hours of life from their plugs?

Harvey

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Re: Oil on spark plugs - Inverted 503

by Roger Lee » 13 years ago

Roger Lee

125 5.11k 4.52k

Hi Harvey,

Never use anti seize on a Rotax engine spark plug. On a 912 it is a thermal conducting paste. On the two strokes they are to be dry, and torqued to 238 in/lbs on a cold engine. Anything else will can cause problems. See page 11-4 in the Rotax 2 stroke maint. manual.

Roger Lee
LSRM-A & Rotax Instructor & Rotax IRC
Tucson, AZ Ryan Airfield (KRYN)
520-349-7056 Cell

Report

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Oil on spark plugs - Inverted 503

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