John McClean 1 Posted January 4, 2022 Share Posted January 4, 2022 Hi. Recently I was given a model with an Irvine 53 engine. I ran the engine and a lot of black muck came out of the exhaust to silencer joint. Looking inside I found the bearings were rusty, it had been lying around for too long. I've cleaned it up and fitted new bearings. When I turn over the engine, without the backplate or the glow plug fitted, I can see and feel the big end 'click' as it goes over TDC. Do I need to change the big end bearing, or put an extra shim under the head, or would metal expansion when it's running alleviate the problem. Regards, John Quote Link to comment Share on other sites More sharing options...
Martin Harris - Moderator Posted January 4, 2022 Share Posted January 4, 2022 Sure it's not just tightness at the top of the piston/bore? There will always be a slight clearance at the big end which would be detectable by eye in these circumstances. An easy test for any ovality would be to see if there's detectable difference at different orientations. Black muck is usually due to aluminium fretting e.g. a loose exhaust flange. Quote Link to comment Share on other sites More sharing options...
Denis Watkins Posted January 4, 2022 Share Posted January 4, 2022 (edited) To add to Martins post, Even a new from the box ABC motor, can click over compression. As the motor reaches temperature, the click disappears. The black stuff does indicate rubbing aluminium surfaces and the test now is for clean oil from a hot run. Edited January 4, 2022 by Denis Watkins Quote Link to comment Share on other sites More sharing options...
John McClean 1 Posted January 4, 2022 Author Share Posted January 4, 2022 Hi Martin. I'll check it at different orientations tomorrow. I think the engine has had very little running time, the piston head is quite clean. The exhaust gasket burned out when I ran it, perhaps I didn't tighten the silencer enough. Have you any suggestions for a material to use for a gasket ? Thanks John Quote Link to comment Share on other sites More sharing options...
John McClean 1 Posted January 4, 2022 Author Share Posted January 4, 2022 Thanks Denis. I'll run it tomorrow. Regards John Quote Link to comment Share on other sites More sharing options...
Martin Harris - Moderator Posted January 4, 2022 Share Posted January 4, 2022 3 minutes ago, John McClean 1 said: Have you any suggestions for a material to use for a gasket ? Yes - nothing! The metal to metal joint should be sufficient and a gasket tends to settle and loosen. I don't recall gaskets being supplied with Irvines unless perhaps OS added one for the later versions? Quote Link to comment Share on other sites More sharing options...
Jon H Posted January 5, 2022 Share Posted January 5, 2022 within reason clicks over TDC are normal as the tolerances stack up. You need clearance around all the parts (big and little end, gudgeon pin in the piston) and all you are feeling is these 3 collapsing one way, and then expanding again the other way. Nothing to worry about 1 Quote Link to comment Share on other sites More sharing options...
Engine Doctor Posted January 5, 2022 Share Posted January 5, 2022 Don't bother with a gasket on the exhaust. They always compress and come loose and if your unlucky you loose the bolts and occasionally the muffler as well. Use a drop of epoxy on the mating exhaust surfaces making sure the bolts have plenty of oil on the thread before tightening. This epoxy will stop any leaks or black gunge . When you want to remove just undo the bolts and tap the exhaust sharply . Quote Link to comment Share on other sites More sharing options...
Nigel R Posted January 5, 2022 Share Posted January 5, 2022 ED, slow stuff or 5 minute? Quote Link to comment Share on other sites More sharing options...
Engine Doctor Posted January 5, 2022 Share Posted January 5, 2022 I have used both but I do prefer the slow stuff as it doesn't go rubbery. It won't glue parts together permanently as they are usually oily but don't clean them with any solvents before assembly. Just a wipe with tissue then apply epoxy and assemble. Quote Link to comment Share on other sites More sharing options...
John McClean 1 Posted January 12, 2022 Author Share Posted January 12, 2022 Hi. Sorry but I got waylaid for a few days. The Irvine 53 is running fine now, I used small bit of silicon gasket sealant at the exhaust flange. I'll have the model finished soon and try it in the air. On a another point, often the engine mounting set screws need to be longer than the space between the exhaust flange and the mounting lug, the head of the screw won't go past the exhaust flange. I've fitted the screws from underneath, i.e. with the nuts on top. Are there any other suggestions? I don't want to grind half the head off ! Regards John Quote Link to comment Share on other sites More sharing options...
Jonathan M Posted January 13, 2022 Share Posted January 13, 2022 (edited) Suggestion 1: If you bore out the two mounting holes on the exhaust side by an extra 0.5mm then you might be able to insert your bolts at just enough of an angle for their heads to clear the flange, and once the heads are clear then the bolts can drop plumb down onto the mount, etc. I wouldn't worry about sloppiness, as the other two holes will be a snug fit to align the engine correctly, and once all the nuts are fully nipped-up the engine won't be going anywhere. Suggestion 2: I haven't measured the difference myself, but perhaps a hex-headed bolt will have a smaller head diameter than a conventional one? Even if this isn't the case then filing just enough of a flat on the outside to clear the flange might do the trick, without compromising the strength of the rest of the head to hold an Allen-key while you nip up the nuts on the other side. Edited January 13, 2022 by Jonathan M Quote Link to comment Share on other sites More sharing options...
John McClean 1 Posted January 13, 2022 Author Share Posted January 13, 2022 Thanks Jonathan, I'll try those tips. Regards John Quote Link to comment Share on other sites More sharing options...
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