nigelog Posted December 8, 2008 Report Share Posted December 8, 2008 I have had a disaster with an experimental bearing I had intended for use on a C15. I wanted to replace the timing bush with something more robust and opted to machine the inner and outer bearing components to fit a needle roller. It was with the assistance of this forum that I managed to get the bearing over from the US. Everything was fine until the machinist took about 8thou too much off of the outer bearing case (and for some reason shortened it to the same width as the bearing) making it unuseable. All the other components, inner sleeve, bearing and thrust washers are perfect. I can only find complete items with the sleeve bush in place at Quote Link to comment Share on other sites More sharing options...
charlie prescott Posted December 9, 2008 Report Share Posted December 9, 2008 Hi Guy's Hi Nige. Proably cheaper to keep an eye on e-Bay for one, or a compleat crankcase as I have seen these for as cheap as Quote Link to comment Share on other sites More sharing options...
nigelog Posted December 10, 2008 Author Report Share Posted December 10, 2008 (edited) Hi Guy's Hi Nige. Proably cheaper to keep an eye on e-Bay for one, or a compleat crankcase as I have seen these for as cheap as Edited December 10, 2008 by nigelog Quote Link to comment Share on other sites More sharing options...
charlie prescott Posted December 11, 2008 Report Share Posted December 11, 2008 H i Guy's. Hi Nige, Thanks for the information , I will try and get one of these bearings,, the one's that Alpha and C and D use and see if my machinist mate and me can't come up with the answer, or perhaps a cheaper finished product ,it should not be that much trouble should it? Yes keep me posted ,and I will you. Regard's Charlie. Quote Link to comment Share on other sites More sharing options...
nigelog Posted December 12, 2008 Author Report Share Posted December 12, 2008 Hi Charlie Alpha sell the bearing @ Quote Link to comment Share on other sites More sharing options...
charlie prescott Posted December 12, 2008 Report Share Posted December 12, 2008 Hi Guy's Hi Nige, Yes I found the bearing on Simply Bearings Last night. I have spoken with my Machinist mate today, and he said it would probably be better to grind the races, and use phospher bronze for the two washer/spacers. that hold the oil presure in. I will order a bearing along with the drivside main and gearbox etc , tomorrow. Another tip I have found out is to use double rubber sealed bearings, and just remove one for the drive side main, keep both in for the rest, and this stops most of the oil leaks. And for the amount of work that a trials bike does,they will be fine with there own lubrication. Will let you know how we get on mate. Good luck with yours in the mean time. Regard's Charlie. Quote Link to comment Share on other sites More sharing options...
b40rt Posted December 12, 2008 Report Share Posted December 12, 2008 Hi Guy's Hi Nige, Yes I found the bearing on Simply Bearings Last night. I have spoken with my Machinist mate today, and he said it would probably be better to grind the races, and use phospher bronze for the two washer/spacers. that hold the oil presure in. I will order a bearing along with the drivside main and gearbox etc , tomorrow. Another tip I have found out is to use double rubber sealed bearings, and just remove one for the drive side main, keep both in for the rest, and this stops most of the oil leaks. And for the amount of work that a trials bike does,they will be fine with there own lubrication. Will let you know how we get on mate. Good luck with yours in the mean time. Regard's Charlie. If you ever pick out the rubber seal on a new bearing you will be shocked at the tiny amount of grease in there, probably worth adding some. Quote Link to comment Share on other sites More sharing options...
nigelog Posted December 15, 2008 Author Report Share Posted December 15, 2008 If you ever pick out the rubber seal on a new bearing you will be shocked at the tiny amount of grease in there, probably worth adding some. I thought long and hard about that and decided against it for the drive side bearing and removed both to provide continuous oil feed. Could have left the outermost but was concerned about crankcase pressure. The sleeve gear bearing I did leave the outermost to help the oilseal keep the muck out. When I stripped engine there was 1/4 inch of what could only be described as MUD in the sump well. I have allowed for gearbox pressure by venting the filler cap with a .8mm hole drilled to vent at the side of the bolt and not the top. Quote Link to comment Share on other sites More sharing options...
b40rt Posted December 15, 2008 Report Share Posted December 15, 2008 I thought long and hard about that and decided against it for the drive side bearing and removed both to provide continuous oil feed. Could have left the outermost but was concerned about crankcase pressure.The sleeve gear bearing I did leave the outermost to help the oilseal keep the muck out. When I stripped engine there was 1/4 inch of what could only be described as MUD in the sump well. I have allowed for gearbox pressure by venting the filler cap with a .8mm hole drilled to vent at the side of the bolt and not the top. I drilled a hole in one of the tappet covers on my B40, it breathes pretty hard through that. Did this several years ago and without tempting fate, reduces oil leakes elsewhere. Quote Link to comment Share on other sites More sharing options...
charlie prescott Posted December 15, 2008 Report Share Posted December 15, 2008 Hi Guy's Seem's nowaday's I can't think of two thing's at once. Sorry Boy's I forgot to say that the breathing in the Scott Ellis Replica bike is simular to the system used in the Mead and Tompkinson, racer of yesteryear, with exeption of the chain case where an oil mist should be sufficiant? you work it out? There is a large tube out of the gearbox filler plug with a T piece. And also a bearing in the gearbox sprocket changing plate. Hope this clears up the confusion. Regard's Charlie. Quote Link to comment Share on other sites More sharing options...
nigelog Posted December 16, 2008 Author Report Share Posted December 16, 2008 Hi Lads on the subject of engine breathing - might as well think of that while I wait for the bearing - I have been toying with the idea mentioned in Ruperts book re:B50 breathing with 2 x 10mm holes drilled from the drive side into the lower crankase. These holes are supposed to be drilled at a height which will act as a weir and hold "engine oil" in the primary case. The primary gear and the engine would therefore share an oil supply. I like the idea of a single oil level to monitor but I have been unable to find out any more details or get sight of a B50 casing to have a look. I think it may provide "too much" breathing for the engine but I would be interested in anyones input. Rgds Nigel Quote Link to comment Share on other sites More sharing options...
b40rt Posted December 16, 2008 Report Share Posted December 16, 2008 Hi Ladson the subject of engine breathing - might as well think of that while I wait for the bearing - I have been toying with the idea mentioned in Ruperts book re:B50 breathing with 2 x 10mm holes drilled from the drive side into the lower crankase. These holes are supposed to be drilled at a height which will act as a weir and hold "engine oil" in the primary case. The primary gear and the engine would therefore share an oil supply. I like the idea of a single oil level to monitor but I have been unable to find out any more details or get sight of a B50 casing to have a look. I think it may provide "too much" breathing for the engine but I would be interested in anyones input. Rgds Nigel What is "to much" breathing ? Quote Link to comment Share on other sites More sharing options...
nigelog Posted December 19, 2008 Author Report Share Posted December 19, 2008 What is "too much" breathing ? I am not so familiar with 4 stroke crankcase compression but surely there is a limit to the amount of airflow provided. Why go to all the trouble of creating a timed/ported breather on the timing side whena hole drilled through the casing would have sufficed or even left the timing gear shaft hollow. The brain cells seem to remember crankcase pressure was required in piston ported 2 strokes to provide the transfer of fuel air. I would be interested to know what influence crankcase pressure or the lack of it has on a 4 stroke Quote Link to comment Share on other sites More sharing options...
charlie prescott Posted December 19, 2008 Report Share Posted December 19, 2008 Hi Guy's Hi Nige. As far as I understand it, it is all down to tolarances of moving parts that contribute to engine pressure buildup's. And to be honest British bikes were never as good at closeness of tolarances as say the bikes built in Japan, and they soon worked it out that if possible an engine gear unit to be kept simple was better with a common oil supply and big breather pipes. Timed breathers were only a comprimise. Only My Idea? Regard's Charlie. Quote Link to comment Share on other sites More sharing options...
nigelog Posted January 20, 2009 Author Report Share Posted January 20, 2009 Hi all, Charlie I finally got my bearing from Alpha and they machined it (ground) to my tolerance which was good of them and very reasonable. I am sticking with my 23mm US bearing so as it matches the shim I made. I also got the 20mm bearing from Alpha to compare it so if you havent bought yours yet I'll swap it for a C15 metal clutch plate (I'm missing 1) and an Amal carb fibre spacer(mine is too small vertically and does not cover the seal all around). Re-assembly starting tomorrow. I also went with the crankcase breathing by drilling 2 x 3/8 holes but I tapped them so that if it does not work out I can block them without separating the crankcases. I also replicated the oil catch (used for the inner timing cam bearing) on the other side of the case to feed extra oil into the primary case. I'll see how I get on. Can be viewed at Http://rebuildbsac15.blogspot.com Quote Link to comment Share on other sites More sharing options...
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