Rotax 912 cylinder head

[P Morel]

My #4 cylinder head on my 912 has a wallowed out exhaust port. I'm certain this is not repairable. Temporary exhaust leak has been fixed but the cylinder head definitely needs replacing.

I'm sure there is a member that might have spare 912 Rotax parts around that they would like to sell.

[kitfox5v]

Paul,
Look on ebay. There is always rotax 912 parts for sale.
Good luck Eddie

[Danzer1]

Curious - What caused it? Did it overheat? Just the one cylinder?

Greg

[P Morel]

Curious - What caused it? Did it overheat? Just the one cylinder?

Greg

No overheating problem. Pilots friends noticed a different sound in my Kitfox 912 than other Kitfox 912's. Since it was gradual for me, I never noticed. I did find there was discoloration on the engine mount close to the #4 cylinder head. I dismissed it. However at one point I found both exhaust studs missing and that explained why the discoloration in that area. The loose pipe rattling around in the exhaust port hole expanded the hole to the point where when I tighten the stub bolts, the clamp would bottom out against the exhaust head. This would not allow any pressure against the exhaust pipe and not seal against the enlarged hole. This only made a bad situation worse.

The lesson here is if something doesn't look right, then there's a reason.

[Danzer1]

Thanks Paul, good info for everyone else to know what to look for.

You might want to consider new valves and pushrods with a new head as they "wear to" their mating parts in the head and your old ones may not seal right in a new head.

If buying used, I'd suggest considering getting the head complete with the valves and pushrods. Critical though would be to make sure they have never been removed and if they have - they have been indexed to their orientation in the head so they can be reinstalled in their "wear mating" orientation. It is impossible to do if they have previously been removed and not marked.

Good luck in your search, kind of an expensive lesson.

Greg

[P Morel]

A very expensive lesson indeed. Thanks for the pointers and I will follow your good advice.

[foxkit3]

Hello. Sorry to here about your exhaust port. I have a extra cylinder head I would sell for a good price

Chris

[mr bill]

There are two versions of the cylinder heads. As I recall cylinders 1 & 4 are the same and cylinders 2 & 3 are the same. If all else fails, send your cylinder head to LEAF airfoil and see what they say. They may be able to salvage it.

[Peteohms]

Call Ronnie at SOUTH MS LIGHT AIRCRAFT. Bet he has what you need and can also advise you.

[mtgsxr]

ohh im going to catch hell for saying this but here it goes... You could have a "qualified" welder heat the head, weld up the area and machine it back to specs.. hav seen it done a lot on motorcycle heads with no issues.

[kitfox5v]

Russ,
I think that's a good idea. What's the worst that could happen? Exhaust leak he already had. Sure saves a lot of $. Sorry I did'nt get to drop by while I was out your way. Maybe next time. Eddie;)

[mr bill]

Cracked cylinder heads on Lycoming and Continental engines have repaired by welding for many years and they operate at much higher cylinder head temperatures than the Rotax, Harrison in Indiana is one company that does it, there are others I'm sure.

[Av8r3400]

If done properly, this could be a valid method of repair.

Keep in mind the extremely tight tolerances of the Rotax engine compared to the old style engines. Proper preheating and welding filler material are critical to keep warping to a minimum. A warped cylinder to head mating surface will render the head junk.

Which is exactly where you are now, so nothing ventured, nothing gained.