Bearing in mind...

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I need to take the mainshaft bearing out of my transmission case, but it doesn't seem inclined to move. The factory manual is rather vague about getting it out. It doesn't even say whether it exits through the inside of the case, or the outside.
 
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Like the others say, in future must read post properly. Heat case to 200 C, if when you spit on the cases it sizzles its hot enough.
 
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Captain Chaos said:
I need to take the mainshaft bearing out of my transmission case, but it doesn't seem inclined to move. The factory manual is rather vague about getting it out. It doesn't even say whether it exits through the inside of the case, or the outside.

The mainshaft bearing exits through the inside of the case. I got mine out by heating the case on my gas barbecue (no kidding). My wife won't let me use the oven in the house!! Of course this means removing the entire gearbox from the bike. After heating to 250F or so, my bearing could be easily removed by simply banging the case on a block of wood. Sometimes they just fall out. I just reversed the procedure to install a new one. For installation, you can also freeze the bearing to increase the difference in temperature between bearing and case. Removal and installation by heating the cases seems to be the preferred method rather than trying to bang them out and risk damage to the bearing or the case.

I also removed the layshaft bearing the same way. Heating is really the only way to remove this one (other than maybe with a puller of some sort) as you can't get behind it. If you upgrade to a new roller bearing for the layshaft, make sure you install it the right way around the FIRST time (ask me how I know this!!) because these new bearings (like SKG, FAG etc.) have polyamine?? cages and should not be heated to the temperatures needed to remove them. Makes the cages brittle. So you want to get it right the first time around!!
 
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tpeever said:
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I also removed the layshaft bearing the same way. Heating is really the only way to remove this one (other than maybe with a puller of some sort) as you can't get behind it. If you upgrade to a new roller bearing for the layshaft, make sure you install it the right way around the FIRST time (ask me how I know this!!) because these new bearings (like SKG, FAG etc.) have polyamine?? cages and should not be heated to the temperatures needed to remove them. Makes the cages brittle. So you want to get it right the first time around!!

This is the only way to remove them without causing damage. I would also suggest wearing gloves when replacing the bearings as you have to put your hand quite deep into the case and if your knuckle touches the hot alloy, you will drop the bearing which will probably fall crooked into its' housing and you'll have to drift it out ! (don't ask how I know this either)

p.s. If you're thinking of heating them in the domestic oven, this will be quite smelly as all the old EP sweats out of the casting. This can be reduced by giving them a go in the dishwasher first ! (I can't believe that I've owned up to that ! -" Yes dear, just coming ! ")
 
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I heated it with a heat gun, but to no avail. The heat gun worked well on the layshaft bearing.

I noticed a large chamfer on the inside of the mainshaft bearing, which would have led me to believe it had been pressed in from the outside. Shows what I know.

The case is having a crack welded right now, but I should have it back by thursday. I'll hit the industrial bearing place friday morning and hopefully reassemble this weekend.

Yay.
 
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You'll struggle to get the case evenly hot with an air gun I think. Best thing is an oven and heat it until a ball of spit bounces off ("No Dear, Of course I haven't been spitting in the oven !" :roll: )

Be careful sourcing the bearing. From memory, they are a modified item with the inner race ground oversize to fit the sleeve gear. A standard bearing with the same markings won't fit.

I think there is little option but to buy one with a little green globe.
 
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Its best to get this bearing from norton suppliers as replacement is an upgraded superblend just like the crank to allow for flex in the shaft. Heat in oven & sharp tap of case onto wood is the way I did it.
 
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Ron L

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I've not seen the Mick Hemmings gearbox video, but I have watched the John Hudson. Frankly, I was disappointed. Watching John chase a gearbox across a table with wooden mallet was not inspiring.

I suggest you go to Fred Eatons website (Old Britts) and follow his excellent pictorial descriptions.

While he doesn't address how to heat the gearbox to remove the bearing, I like his technique for crankcase bearings. Especially since we are in the winter season. He simple puts the case on his kerosene heater until the bearing drops out! Brilliant! It should also work for gearbox bearings.

I have done at least a dozen gearboxes, and the most overlooked bearing is the layshaft bushing in the kickstart shaft. I never replace the layshaft bearing in the case without replacing the bushing supporting the other end in the kickstart shaft. The easiest way I have found to do this is with a 3/4 inch tap and appropriate bolt.
 
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One of my contacts in Brit Bike cyberworld was also disappointed with the John Hudson video because John apparently used a torch to heat the case and was drifting the bearings out rather than using the oven heating method we have described. I have never seen the video so can't comment directly but my contact's review of that particular movie was not "two thumbs up". His response was "gentlemen should not bash their bearings"
 

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Both NOC John Hudson engine and gearbox rebuild videos do also make me cringe a little here and there, as his tools and methods would be considered rather basic by modern standards at least!

But he was the factory service manager for many years, and would regularly travel to a Norton owner's house to fix a major fault on their machine carrying no more than a bag of tools strapped to the pillion seat of his motorcycle. The repair being done wherever he was able to do it, even on the kitchen table if necessary. So for anyone to say that he didn't know what he was doing would be seriously wide of the mark, and in the videos he does heat casings with a torch, but if done correctly then there's nothing wrong with that! He certainly does remove the bearings by tapping the casings on blocks of wood although he does gently tease the odd bearing out with a punch if it appears to be a little tight to hurry things along a bit (after all the cameras are rolling!) and I'm sure he would have been able to strip an engine in the time most of us would spend thinking about it and be able to quote the part number, thread type and dimension of each part he handled as he did so.


John was also President of The Norton Owners Club for many years, unfortunately some while after making the videos he started to suffer badly from Alzheimer's disease, he eventually died in January 2003.
 
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