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Nov 28, 2019, 10:07 AM
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OS 46 AXii Head Gasket Removal

My OS 46 AXii was percolating fuel between the head and cylinder so I assumed a bad head gasket was at fault. I ordered a new gasket and then removed the head. Now I'm not sure that was the problem. First of all, I don't know how to get the old gasket out of the head, any help with that would be appreciated. Second, from what I can see of the gasket in the head, it really doesn't appear to be cracked or broken. The head bolts weren't loose, but they weren't extremely tight either. Could it be that the head just wasn't tight enough and that caused the leak? Or, maybe the head is cracked. Any way to check that? The problem made a real mess of the motor (tarnished). Any good ways to clean the head and cylinder? Thanks for the advice.
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Nov 28, 2019, 10:29 AM
An itch?. Scratch build.
eflightray's Avatar
Welcome to RCGroups

Sadly you found the 'Electric' Power forum, here's the one you need ---

Aircraft Fuel General - Engines

Hope that helps.

Nov 28, 2019, 11:55 AM
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Thank you. Sorry for the mis-post. Copied over Fuel Engines. Thanks for the heads-up eflightray.
Nov 28, 2019, 08:24 PM
Registered User
Sometimes fuel spits back out of the carb landing where it wants to on the engine . I assume your a beginner judging by your engine and number of posts . Sorry if Im wrong wit dat ! Did the engine get over heated at any stage ? that might cause stretched head bolts , warped head etc . The gasket is actually a shim but whatever . Normally on a engine that hasnt been apart before the bolts let go with a distinctive crack . I would re tighten them and fire it up and see what happens . You do need to get this sorted though . Cheers
Nov 29, 2019, 11:17 AM
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Yes, I am fairly new at this hobby. The engine was brand new when I first started with it and I don't think it has overheated but can't say for sure. I am going to put the head back on, tighten the bolts down and run it on an engine stand to see how it acts. I hope the bolts were just loose enough to allow the fuel to bubble out between the head and cylinder. Thanks for your advice Pope.
Nov 29, 2019, 07:34 PM
Registered User
do let us know how it goes . Cheers
Nov 30, 2019, 06:16 AM
Diesel Danny
danny mz's Avatar
G'day Jim.

It is unusual for a quality engine such as your O.S. to develop a cylinder head leak but I have seen this before so not impossible.

If you have definitely traced the leak to the head (as pope said carburetor blow-by residue can appear in weird places, depends on cowling and airflow ) then check for minute traces of crud at the head/cylinder seal.

If there is a leak it usually appears as a burn mark on the head/cylinder interface near the culprit area.

Many model engine manufacturers used to advise to check the head bolts after the first few runs so they were presumably aware that this was a potential problem.

When you re-fit the head tighten the head bolts in a diagonal pattern, eg, (clock dial) 12-6-10-4-2-8 using your fingers on the short end of your hex-key initially until just snug then repeat the pattern a bit firmer still using the short end to apply the torque.

If you want more torque then use the long end of your hex-key. Keep the deflection consistent on each head bolt and follow the pattern.

I check my head bolts using one of these - total overkill but I have one for other uses and can assure you that 15in/Lb is adequate for most model engine cylinder head bolts https://www.australiantacticalprecis...-piece-bit-set

To clean the crapola from your engine, this is what I usually see advocated for use in the U.S. I use the Aussie equivalent which also works well.

* Danny M *

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