Nigel R Posted May 2, 2022 Share Posted May 2, 2022 Frustrating to say the least. I have an os with a silencer, the old style, that insists on coming loose every flight. I'm sure at this point the aluminium thread on the can is probably fretted away too much to rescue and the thing will never stay tight. I'm about in the point of ordering one of the just engines replacements. Open to any suggestions on keeping the cans done up, anyone suffered the same issue and cured it? Epoxy in the thread? Thread locker? Quote Link to comment Share on other sites More sharing options...
john stones 1 - Moderator Posted May 2, 2022 Share Posted May 2, 2022 Blue thread lock. Quote Link to comment Share on other sites More sharing options...
J D 8 Posted May 2, 2022 Share Posted May 2, 2022 Blue thread lock and put some on the engine/exhaust mating surface as well as the bolts. Quote Link to comment Share on other sites More sharing options...
dave windymiller Posted May 2, 2022 Share Posted May 2, 2022 Dont use a gasket! Quote Link to comment Share on other sites More sharing options...
Martin Harris - Moderator Posted May 2, 2022 Share Posted May 2, 2022 Is this a 4 stroke or a 2 stroke? Which engine size/version? Quote Link to comment Share on other sites More sharing options...
Nigel R Posted May 3, 2022 Author Share Posted May 3, 2022 Oops! 81 four stroke, using a baffled can from JuSt engines. Quote Link to comment Share on other sites More sharing options...
Christopher Wolfe Posted May 3, 2022 Share Posted May 3, 2022 Also, check that the prop is balanced and that the engine mount screws are tight. Vibration causes things to loosen so it could be a case of 'prevention is better than the cure'. Quote Link to comment Share on other sites More sharing options...
Nigel R Posted May 3, 2022 Author Share Posted May 3, 2022 Good call, but checked already - Prop is balanced and mount is all tight at firewall and motor. Quote Link to comment Share on other sites More sharing options...
Engine Doctor Posted May 3, 2022 Share Posted May 3, 2022 (edited) Hi Nigel don't use a gasket etc . Apply a thin bead of epoxy around the edge of the mounting flange. I use the standard 24 hour epoxy for this. Make sure the screws threads are oiled and just them screw up. It will make an oil tight joint and secure the exhaust. When you want to remove it simply unscrew the two fixing screws and give the dilence a sharp tap. Also make sure that the prop is balanced as vibes fro unbalanced prop can shake exhausts loose besides causing other failures on engine and airframe. Edited May 3, 2022 by Engine Doctor Quote Link to comment Share on other sites More sharing options...
ken anderson. Posted May 3, 2022 Share Posted May 3, 2022 hello NR...i always use/used clear silicone on the bolts after the joint was made...cover them completely...it always worked and if needed to remove was easily done. ken anderson...ne..1...silicone dept. Quote Link to comment Share on other sites More sharing options...
Engine Doctor Posted May 3, 2022 Share Posted May 3, 2022 (edited) Hi Nigel ignore my previous post it was for a two stroke muffler. Had visitor and run out of time to edit post . If thread is damaged or worn in a four stroke head then it's very difficult to get a tight fitting that will remain done up. Also almost impossible to repair as very little material around the head fitting. Epoxy won't work as the fs exhaust gets too hot. Try fitting a bracket to the can that then fits to an engine bearing bolt . This will support the can and take some strain off of the exhaust fitting in the head. Only other remedy will be to find a head with a good thread . Edited May 3, 2022 by Engine Doctor Quote Link to comment Share on other sites More sharing options...
Nigel R Posted May 3, 2022 Author Share Posted May 3, 2022 Thanks ED Fortunately the thing coming loose is the can itself - not the threaded coupler at the motor end. That end of things has always been solid. Bracket for support sounds good, but would that still aply? When first fitted, I had a flexi pipe joining the standard coupler to the can, and the can was mounted on a bracket. The can came loose whilst on this arrangement (right before the flexi pipe cracked) Perhaps the thread has always been a bit loose or worn? Quote Link to comment Share on other sites More sharing options...
Engine Doctor Posted May 4, 2022 Share Posted May 4, 2022 (edited) OK if its just the can try the following . Tighten fully and run up to full temp and stop engine. While still hot snug up the lock nut again. Using two spanners , one on nut other on can. It's always worked for me. Of course if thread is very loose it may be time yo find a new can. When loose they wear very quickly when engine is running as shown by a lot of grey oil residue. E.D. Edited May 4, 2022 by Engine Doctor Quote Link to comment Share on other sites More sharing options...
David Ovenden Posted May 4, 2022 Share Posted May 4, 2022 I have found what ED suggests above to work well if tve thread in the cab is a little worn you could try wrapping some PTFE pipe tape round the manifold pipe before you screw the can on. Then follow the steps as outlined by ED above. Has worked in the past for me Quote Link to comment Share on other sites More sharing options...
Nigel R Posted May 4, 2022 Author Share Posted May 4, 2022 (edited) Hmm. Sadly it's been snugged when hot - first thing I tried. I haven't tried PTFE tape yet... I do have a roll of the stuff. Will try that before splashing out on a new can. The can itself was second hand, it came from a 91 that also boasted a warped crankcase and bent rod (advert read along lines of "runs great, excellent condition", hmm, I think not). Just noticed I made an error earlier in the thread, Quote 81 four stroke, using a baffled can from JuSt engines. actually should say I'm using a baffled can from OS 91, I'm thinking of buying a baffled can from JE, obviously one of my friday afternoon quality posts there Edited May 4, 2022 by Nigel R Quote Link to comment Share on other sites More sharing options...
Nick Somerville Posted May 5, 2022 Share Posted May 5, 2022 If you decide to change the muffler and want to reduce noise I highly recommend the Weston four stroke quiet pipes. I have one for my Wot4 XL OS 120 pumped combo and it is has a superb soft note that is often commented on. Quote Link to comment Share on other sites More sharing options...
Nigel R Posted May 5, 2022 Author Share Posted May 5, 2022 Thanks Nick, they look interesting. How do fix to the header, flexi + clamp? Don't suppose you have a photo of the 120? Quote Link to comment Share on other sites More sharing options...
David Davis Posted May 6, 2022 Share Posted May 6, 2022 22 hours ago, Nick Somerville said: If you decide to change the muffler and want to reduce noise I highly recommend the Weston four stroke quiet pipes. I have one for my Wot4 XL OS 120 pumped combo and it is has a superb soft note that is often commented on. That's interesting. I was thinking of adding one to the OS 52 in my Baron and flying it in La Coupe Des Barons next month, after all I've a title to defend now! ? Whispering Death indeed! 1 Quote Link to comment Share on other sites More sharing options...
Nick Somerville Posted May 6, 2022 Share Posted May 6, 2022 15 hours ago, Nigel R said: How do fix to the header, It screws directly into the cylinder head with a nut to nip it up. Photo to follow shortly. Quote Link to comment Share on other sites More sharing options...
Nigel R Posted May 6, 2022 Author Share Posted May 6, 2022 ah, ok - couldn't see a threaded portion on the weston site - interesting Quote Link to comment Share on other sites More sharing options...
Nick Somerville Posted May 6, 2022 Share Posted May 6, 2022 In my case the pressure nipple has been blocked off as the engine is the pumped version. As I bought the model and engine together 2nd hand I had assumed the pipe and header had come together but now thinking about it, probably a separate purchase by the original owner. BTW the engine is the Surpass MK2 pumped 120 and is one of the nicest engines I have ever owned. It needed new bearings when I first got it (thanks Jon) but since has run flawlessly. In particular it has such a responsive and smooth throttle curve. 1 Quote Link to comment Share on other sites More sharing options...
Nigel R Posted May 6, 2022 Author Share Posted May 6, 2022 nice one Nick - many thanks explains why I couldn't see the thread! are they particularly heavy units? now very interested, if I'm going to spring for a new can, it might as well be one that does the biz, as it were Quote Link to comment Share on other sites More sharing options...
Nick Somerville Posted May 6, 2022 Share Posted May 6, 2022 Seems very light to me. Quote Link to comment Share on other sites More sharing options...
Engine Doctor Posted May 7, 2022 Share Posted May 7, 2022 (edited) Alan of Weston UK made me Silencer for a Moki 50cc FS . It sounded very quiet and was light but strong. Far better and stronger than the original that fell to bits , even the importer said were a bit rubbish. Edited May 7, 2022 by Engine Doctor Quote Link to comment Share on other sites More sharing options...
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