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Tech. Advice: Series 'B' / 'C' 500cc/1000cc Bikes
Burman 4th Gear Selector Meltdown
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<blockquote data-quote="Matty" data-source="post: 30271" data-attributes="member: 1339"><p>Hi</p><p></p><p>About 5 years ago I found that my clutch was loose on the mainshaft gearbox splines. The gearbox splines were fortunately perfectly OK, but the "clutch centre" (PR50 2x ?) splines/dogs were very worn due to a little slackness having developed in the big fixing nut holding the clutch to the mainshaft. So little was left of these dogs in fact, that they would probably have soon sheared off and all drive would have been lost</p><p></p><p>I had to buy a new clutch centre (from Conway Motors) for around £80 to fit properly onto the mainshaft and have since done the nut up as tight as I dare onto its tabwasher to prevent this happening again.</p><p></p><p>With all due respect to Burman, I feel that the design of this is not really very good, because the full torque of the engine power (or overrun) multiplied by the ratio of the primary drive is being applied to loosen the centre nut. However it can't be too bad because mine had given no real trouble for 60 years !!</p><p></p><p>If you look back through this long saga you will see that I have replaced my mainshaft bearings with sealed ones (have kept the seals in both sides) from <a href="mailto:barkers@engrs.wanadoo.co.uk">barkers@engrs.wanadoo.co.uk</a> because the large bearing at the drive end is a very unusual size (72mm outside and 1.500" inside diameter by 17mm wide)</p><p></p><p>I also used a modified spacer, oil seal and oil seal housing assembly from Draganfly -( BA 1948-52) behind the output bearing circlip and bearing which seems a much better arrangement than the original one.</p><p></p><p>Hope this may be of help to somebody.</p><p></p><p>Matty</p></blockquote><p></p>
[QUOTE="Matty, post: 30271, member: 1339"] Hi About 5 years ago I found that my clutch was loose on the mainshaft gearbox splines. The gearbox splines were fortunately perfectly OK, but the "clutch centre" (PR50 2x ?) splines/dogs were very worn due to a little slackness having developed in the big fixing nut holding the clutch to the mainshaft. So little was left of these dogs in fact, that they would probably have soon sheared off and all drive would have been lost I had to buy a new clutch centre (from Conway Motors) for around £80 to fit properly onto the mainshaft and have since done the nut up as tight as I dare onto its tabwasher to prevent this happening again. With all due respect to Burman, I feel that the design of this is not really very good, because the full torque of the engine power (or overrun) multiplied by the ratio of the primary drive is being applied to loosen the centre nut. However it can't be too bad because mine had given no real trouble for 60 years !! If you look back through this long saga you will see that I have replaced my mainshaft bearings with sealed ones (have kept the seals in both sides) from [EMAIL="barkers@engrs.wanadoo.co.uk"]barkers@engrs.wanadoo.co.uk[/EMAIL] because the large bearing at the drive end is a very unusual size (72mm outside and 1.500" inside diameter by 17mm wide) I also used a modified spacer, oil seal and oil seal housing assembly from Draganfly -( BA 1948-52) behind the output bearing circlip and bearing which seems a much better arrangement than the original one. Hope this may be of help to somebody. Matty [/QUOTE]
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Tech. Advice: Series 'B' / 'C' 500cc/1000cc Bikes
Burman 4th Gear Selector Meltdown
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