i12fly Posted February 25, 2011 Share Posted February 25, 2011 I've got an SC 91 FS with rusty bearings including the camshaft bearings. (I know I should have been more careful on ebay, but when I received it I didn't examine it properly!). Now I've come to check it the engine is very gummy inside as well. I've heated it in the oven at 175deg as I would for a 2 stroke, and removed the main bearings OK, but the camshaft bearings seem like they wont move..... Can anyone advise the best way to remove them? Quote Link to comment Share on other sites More sharing options...
Alan Cantwell Posted February 25, 2011 Share Posted February 25, 2011 its not easy, replace the crank, and the crancase backplate, heat the engine case up, get a block of wood, bring the crankase down onto the opposite mounting lug to the bearing, replacing the bits and bobs is to reinforce the engine, so it does not fracture, even then, its a dodgy one, replace the camshaft cover, and do the same, pref when its still hot, dont forget the oven gloves Quote Link to comment Share on other sites More sharing options...
Engine Doctor Posted February 26, 2011 Share Posted February 26, 2011 You really need access to an expanding puller/mandrell.easy to make and if you have a friend with a lathe its even easier This is inserted into the bearing then expanded and used to pull the bearing from its seating after heating. You can remove them with snug fitting piece of rod or screw gently tapped into the bearing before heating then used to pull the bearing out .I made an expanding puller for a stubborn OS 20 some years ago but generally use the screw or rod method unless I get a difficult one then the lathe gets switched on As Alan says tapping the case can cause distortion . Hope it helps . Quote Link to comment Share on other sites More sharing options...
Ralph Yeates Posted February 26, 2011 Share Posted February 26, 2011 Alan c is correct the engine needs about 25 mins @ 180 C in the oven. Sound like a chef Quote Link to comment Share on other sites More sharing options...
Alan Cantwell Posted February 26, 2011 Share Posted February 26, 2011 i only cook books expanding mandrels are the way to go, but i tried to give the man in the street method, such a mandrel is not easy to produce, and i do it for a living but i might just sit down, and design a universal one one day, i have several older 4 bangers that need work, might be a worthwhile tool Quote Link to comment Share on other sites More sharing options...
Martin Harris - Moderator Posted February 26, 2011 Share Posted February 26, 2011 The entire range of OS and clones up to the ASP/SC 180 use the same bearings for the camshaft so making a universal one should be straightforward! I knocked up an expanding mandrel a few years back ...dimensions aren't particularly critical - the lip needs to be small enough to go in the space behind the bearing and marginally larger than the bearing inner diameter. The expanding rod is simply a piece of 3mm studding heated to red hot and shaped into a blob with a small hammer - then turned as a reverse cone to expand the puller end. You can lock it in place with the nut if you feel the need... Hasn't let me down yet!Edited By Martin Harris on 26/02/2011 15:00:15 Quote Link to comment Share on other sites More sharing options...
i12fly Posted February 26, 2011 Author Share Posted February 26, 2011 Thanks very much for the help and advice, I'll have a go at an expanding mandrel. I got the main bearings today £8 for the pair from Derby Bearings and the counter staff were very helpful so I'm well pleased up to now. The engine could still work out to be a bargain? Quote Link to comment Share on other sites More sharing options...
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