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What have I done

whats wrong with my engine

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Martin Harris23/04/2019 23:25:32
8726 forum posts
214 photos

As long as there isn't too much wear on the seating areas.

Was there much damage to the piston or cylinder? You may get away with just replacing the valve and springs if not. Was it a broken spring or did the valve or retainers fail?

This is a link to the parts listing/diagram I found...

Check the bearings while it's apart - hopefully they are standard sizes which are cheap to replace if you buy them from a bearing specialist and any sign of rusting means they are likely to fail sooner rather than later. I use Simply Bearings who have always been extremely fast and reliable but other suppliers are available, as they say!  I order C3 clearance which I believe are better suited for model engine use although there are better qualified people on this forum who may advise.

Edited By Martin Harris on 23/04/2019 23:36:12

Engine Doctor24/04/2019 09:46:37
2267 forum posts
25 photos

When assembling Camshaft back into assembled engine you can hold the ball bearing in place in the camshaft with a small smear of vaseline or grease . Crank looks a bit corroded ? Are the bearings similarly rusty/ corroded? If they show any signs of corrosion replace them. Even if they feel smooth they will shortly fail and could do more damage to the engine . If you have a vernier gauge and can measure the bearings then Simply bearings are the people to order from or if you cant measure them the Model Fixings would be the people to talk to ..

If valve is bent then in all likelyhood the valve guide is also damaged , Do check before ordering any   bits or bearings as a new head may be required and this may make repair un-economical

The ball bearing used instead of twin ball-races must have been OS cost cutting exercise. From memory ( I may be wrong and will check an engine  later ) the much earlier 20FS had twin races .

Edited By Engine Doctor on 24/04/2019 10:02:12

Jon - Laser Engines24/04/2019 09:53:04
4765 forum posts
179 photos
Posted by Martin Harris on 23/04/2019 23:13:38:

I've found an exploded view of this engine as I've never stripped a 30 but incredibly, the camshaft IS carried by single ball bearings in the ends, not ball races!


Edited By Martin Harris on 23/04/2019 23:18:41

thats a new one on me as well. Very strange setup!

As the others have said, its worth checking the other bearings and replacing them. Usually os rear bearings are metric but front bearings imperial so watch out for that.

ken anderson.24/04/2019 12:51:49
8424 forum posts
772 photos

something is not right here, you say in your opening of this thread that you bought the engine as unused? I have the same engine in a model(JNR 60)and fired it up a couple of weeks ago(using an electric starter also) for the first time probably in 12 months..fired up and went like a goodin….methinks your engine might have been twiddled on with before you got it? taking the cam cover off,would cause the B/B to fall out,i cant think the problem would be there.i had a OS 91/FS exhaust spring snap during a flight,and the engine just stopped damage to it(apart from the broken valve spring)….be interesting when you do find out the damage....

ken anderson...… ne...1 OS 30 dept.

Paul Marsh24/04/2019 20:40:45
3664 forum posts
1038 photos

Seems the engine has had a lot of use for an unused engine. The marks on th crankshaft where the bearing shows it.

Martin Levy24/04/2019 22:53:09
56 forum posts
30 photos

Paul - the engine was unused but I have been using it for about 40 flights.

Ken- a valve spring had broken and the valve was bent and dropped into the cylinder. have ordered a new valve assembly and hope that fixes the problem.

Peter Miller25/04/2019 09:02:29
10062 forum posts
1189 photos
10 articles

I would guess that the valve dropped first and then got bent.

Geoff Sleath25/04/2019 10:38:18
3296 forum posts
251 photos
Posted by Peter Miller on 25/04/2019 09:02:29:

I would guess that the valve dropped first and then got bent.

If my experiences with the odd vintage motor cycle is anything to go by I'd certainly agree, though the broken valve spring may well have contributed by allowing the valve to hit the piston.


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