Lay shaft bearing failure - again!

davidjoyner

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After replacing a blown big end about 10,000 mls ago I put the lay shaft in the wrong way around with consequent lay shaft bearingfailure (non drive side) about 3000 mls later on a trip to Ireland. Used the "riders list" and was helped by Peter in Dublin - wonderful host - but I still had the lay shaft in backwards. I then stacked the bike into a roundabout on the way home- boy does it hurt as you get older! While the repair work was being done I had the gearbox looked over by Conways - sorted! 6000 mls later I've blown that bearing again! The sprocket came loose got a bit beaten up on the end face against the output gear,also the seal was quite deep in the casing, net result the oil was lost and back home on the RAC lorry --------and NZ are world champions------what a grinder of a game, anyway where was I?
The question finally - is there a good publication that will tell me where the mashed up shim went and how much end float etc. Also the sprocket has been rubbing against the casing, what caused that!
This time I'm going to put sealed bearings in - could this be my next disaster! I've got to avoid the sniggering from the family when the RAC truck rattles up outside..currently about every 18mnths!
 

clevtrev

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After replacing a blown big end about 10,000 mls ago I put the lay shaft in the wrong way around with consequent lay shaft bearingfailure (non drive side) about 3000 mls later on a trip to Ireland. Used the "riders list" and was helped by Peter in Dublin - wonderful host - but I still had the lay shaft in backwards. I then stacked the bike into a roundabout on the way home- boy does it hurt as you get older! While the repair work was being done I had the gearbox looked over by Conways - sorted! 6000 mls later I've blown that bearing again! The sprocket came loose got a bit beaten up on the end face against the output gear,also the seal was quite deep in the casing, net result the oil was lost and back home on the RAC lorry --------and NZ are world champions------what a grinder of a game, anyway where was I?
The question finally - is there a good publication that will tell me where the mashed up shim went and how much end float etc. Also the sprocket has been rubbing against the casing, what caused that!
This time I'm going to put sealed bearings in - could this be my next disaster! I've got to avoid the sniggering from the family when the RAC truck rattles up outside..currently about every 18mnths!
If the sprocket has been rubbing the case, that will tell you that the output bearing has moved inboard.
The shim that you have that is mashed up goes between the input bearing and the fixed gear on the mainshaft.
There should be no endfloat on the mainshaft, because the output shaft is pulled up to the drive side case, and the clutch shaft is pulled up to the G2 cover bearing. Your mashed up shim would have come from the clutch nut working loose, and allowing the shaft to float, what happens then , is that the shaft then hits the output shaft.
 

davidjoyner

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Thanks for that.. very helpful, would this shim, for re-ordering purposes be G20 and if so what is E76 in the spares list?
 

davidjoyner

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Rapide gearbox goil

Hi - not sure if I thanked you for all that - thanks. I've done about 300 mls with the sealed bearings and all feels well. Drained the oil (20/50) and it had traces off brass "smearing" in it but feel this will clear up soon. Annoyingly there is a gentle oil drip showing from somewhere in the gearchange housing. I am too busy riding this thing to take it apart again! Question is - now that I have gone for sealed bearings throughout the g/box could I use a thicker oil or even some sort of grease? I have read a thread from Peter Moy but that is largely Burman related - consenus seems to EP80.. any ideas on this.
Regards Dave
 
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John Cone

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I think that most use engine oil in a twins gearbox. The drip from the gearchange cover could one of two things, 1st Is there a cork seal in side the kickstart quadrant shafts hole inbound of the top hat bush or have you overfilled the gearbox so oil can track along the gear selector shaft and run down the inside of the cover and out of the bottom? 2nd There could be a slight leak of oil from the valve lifter assembly which drips and runs down between the engine steady plate and the crankcase and out of the bottom and hangs the the kickstart cover/engine plate. If it's engine oil it'll be black.
 

davidjoyner

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Its been standing o/night with no oil in the gearbox and still has an engine oil looking drip off the bottom the cover grr. Its not the cork as I gave that a shot of silicone during re-assembly. The oil is probably residue but I had the oil over the top level on the stick. I'll put thicker oil in and not so much, will report back. I have a successfull mod from Russell Kemp on the valve lifter but will keep an eye on this too. Thanks for the response. Yours Analy Dave.
 

clevtrev

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Its been standing o/night with no oil in the gearbox and still has an engine oil looking drip off the bottom the cover grr. Its not the cork as I gave that a shot of silicone during re-assembly. The oil is probably residue but I had the oil over the top level on the stick. I'll put thicker oil in and not so much, will report back. I have a successfull mod from Russell Kemp on the valve lifter but will keep an eye on this too. Thanks for the response. Yours Analy Dave.
Have you considered that the leak may be from the output shaft ?
EP90 in the gearbox.
 

davidjoyner

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I did, and put an O ring on it behind the kick start gear. I put EP 80 in today at half way up the stick. Should go for a couple of rides over the week end - keep my fingers crossed . Many thanks
 

davidjoyner

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Yes halfway up the flat.. still leaking - ha bloody ha, even when stationery. Next move will be the cleaning and then talc..but still not taking a single nut off! No way, it can leak till Xmas and beyond.
 
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