Martin Levy Posted April 22, 2019 Share Posted April 22, 2019 Just after posting in another thread about fixing engines I started my OS 30FS today and the rubber cone in my starter flew out, jolted the engine and now the prop turns either way half a turn and then jams solid. I bought it unused only 6 months ago What could I have done? Martin Quote Link to comment Share on other sites More sharing options...
Simon Chaddock Posted April 22, 2019 Share Posted April 22, 2019 I fear something is seriously amiss that will require some disassemble to identify the problem. Do not do this unless you really know what you are doing and most definitely do not try to force it to turn! Quote Link to comment Share on other sites More sharing options...
Martin Harris - Moderator Posted April 22, 2019 Share Posted April 22, 2019 I'm afraid your crankpin has probably sheared. It's a bit like bolting the door after the horse has bolted but did you turn the engine by hand before trying to start it? If the cylinder has flooded with fuel, a hydraulic lock can occur and the starter can then do serious damage. The cone coming out was probably due to the engine locking, not the cause of the problem. It's also possible that a manufacturing defect, normal wear and tear or corrosion during storage has started a tiny crack which has caused the failure - this can sometimes happen while an engine is in use. Starting small engines with a starter is something that must be done with particular care - the reverse flick technique is often the best way if the engine is well set up. The good news is that often the only damage is to the pin when this happens during a start and a replacement crankshaft may be the only part needed if you're lucky. Quote Link to comment Share on other sites More sharing options...
Steve Hargreaves - Moderator Posted April 22, 2019 Share Posted April 22, 2019 Yes indeed....I fear a sheared crank pin.....same thing happened to my ASP91 a while ago.... Removing the back plate is a fairly simple task & should confirm (or hopefully deny) my diagnosis... Quote Link to comment Share on other sites More sharing options...
Peter Miller Posted April 23, 2019 Share Posted April 23, 2019 If the crank pin has sheared I would expect the shaft to turn more than half way as there is no pin on the crank web to stop it. A broken big end is more likely but even that would allow the crank to turn more than half way A valve dropping into the cylinder could do it. A quick look under the rocker cover would confim confirm that. Quote Link to comment Share on other sites More sharing options...
Paul Marsh Posted April 23, 2019 Share Posted April 23, 2019 If you can get one, a Crankcase if £39 plus postage from JE Con Rod: £12 Quote Link to comment Share on other sites More sharing options...
ken anderson. Posted April 23, 2019 Share Posted April 23, 2019 hard lines there martin, probably a broken c/shaft or hopefully something a bit more minor.as has been mentioned take of the back plate and have a look, get ready to spend some dosh...... ken anderson...ne......1..... dosh dept. Quote Link to comment Share on other sites More sharing options...
Former Member Posted April 23, 2019 Share Posted April 23, 2019 [This posting has been removed] Quote Link to comment Share on other sites More sharing options...
Jon H Posted April 23, 2019 Share Posted April 23, 2019 a busted rod or dropped valve are the most likely candidates but i wouldnt rule out the crank pin as they are relatively easy to bust. Quote Link to comment Share on other sites More sharing options...
Martin Levy Posted April 23, 2019 Author Share Posted April 23, 2019 I took the engine apart and indeed the valve was bent and had dropped into the cylinder. However notice even after removing there was still a jam. I will check the crank pin as there was a loose ball bearing in there from the end of the pin. Crank shaft seems fine though t Quote Link to comment Share on other sites More sharing options...
Martin Levy Posted April 23, 2019 Author Share Posted April 23, 2019 And another question. why was there a ball bearing loose under the camshaft cover. Is this supposed to be attached to the end of the camshaft? there is one fixed in the other end and looks like a recess where it had fallen out of the other. Does this mean I need a new camshaft as well? Quote Link to comment Share on other sites More sharing options...
Jon H Posted April 23, 2019 Share Posted April 23, 2019 im not sure i follow. if the crank shaft is undamaged, ie it still has its crank pin, there should not be much to check. A loose ball bearing, and by that i mean one loose steel ball floating around, is usually pretty terminal so i assume its a different issue. For the valve, i would imagine the valve spring broke and this allowed the retention hardware to fall out and the valve to drop. if the spring is intact then it likely got stuck due to oil or rust....but then there would have been no compression from the get go. If in doubt, post some photos so we can see the situation Quote Link to comment Share on other sites More sharing options...
Martin Levy Posted April 23, 2019 Author Share Posted April 23, 2019 so to try and explain better. I opened the canshaft cover and there was a loose single bearing. On the innermost end there is a visible beaqring set into the end of the camshaft and on the outer end (the one you see when opeing and before removing there looks like a recess where that bearing came from. I cannot see how else a bearing got in there. I hope this makes sense but if not I could post some photos Quote Link to comment Share on other sites More sharing options...
Martin Harris - Moderator Posted April 23, 2019 Share Posted April 23, 2019 Is it a single ball? If its an 1/8 of an inch in diameter or larger it sounds like the main bearing has broken up. Have you removed the backplate yet? It's just a case of removing the carburettor and the backplate - in normal circumstances there's nothing loose under it so you can remove it without fear of things exploding outwards! Quote Link to comment Share on other sites More sharing options...
Martin Levy Posted April 23, 2019 Author Share Posted April 23, 2019 yes Martin. I have now stripped it right down with the exception of the main bearings Quote Link to comment Share on other sites More sharing options...
Jon H Posted April 23, 2019 Share Posted April 23, 2019 i think i understand. It sounds like the bearing (the whole thing, not just a ball) has come out of the cam chest cover and is stuck on the end of the camshaft. This is not the end of the world and not really any sort of problem as long as it isnt shot. If it is, its a stroke of luck as its one less bearing to remove! Quote Link to comment Share on other sites More sharing options...
Martin Levy Posted April 23, 2019 Author Share Posted April 23, 2019 Quote Link to comment Share on other sites More sharing options...
Martin Levy Posted April 23, 2019 Author Share Posted April 23, 2019 1st pic is the crankshaft - looks ok to me (I hope) 2nd pic - one nd of the cam shaft and next to it a bearinf that was loose under te4 cam shalft cover 3rd pic - the other end of the cam shaft with a bearing fixed in it and the pic below which is the cam shaft recess and that bearing was loose in there. New camshaft as well or drop that bearing back in? Quote Link to comment Share on other sites More sharing options...
Martin Harris - Moderator Posted April 23, 2019 Share Posted April 23, 2019 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 Quote Link to comment Share on other sites More sharing options...
Martin Levy Posted April 23, 2019 Author Share Posted April 23, 2019 thanks Martin. So I should be ok just placing that bearing back without having to buy a new camshaft? Quote Link to comment Share on other sites More sharing options...
Martin Harris - Moderator Posted April 23, 2019 Share Posted April 23, 2019 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 Quote Link to comment Share on other sites More sharing options...
Engine Doctor Posted April 24, 2019 Share Posted April 24, 2019 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 Quote Link to comment Share on other sites More sharing options...
Jon H Posted April 24, 2019 Share Posted April 24, 2019 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. Quote Link to comment Share on other sites More sharing options...
ken anderson. Posted April 24, 2019 Share Posted April 24, 2019 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 mid-air...no 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. Quote Link to comment Share on other sites More sharing options...
Paul Marsh Posted April 24, 2019 Share Posted April 24, 2019 Seems the engine has had a lot of use for an unused engine. The marks on th crankshaft where the bearing shows it. Quote Link to comment Share on other sites More sharing options...
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