So You Just Bought a Near Mint Condition Commando?
- Thread starter Dan1950
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My Mk3 exhibited early symptoms at an alleged 20k miles, so was subjected to a complete overhaul kit. But will admit I didn't take a lot of notice of what came out....
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Although the 06-7710 roller bearing part number is listed in the Mk3 parts book as superseding the 040100 (ball bearing) all Mk3s seem to have had the Portuguese* 6203 brass cage ball bearing that has the highest rate of failure.
*(not all are marked 'Portugal')
The brass cage 6203 I removed from my Mk3.
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Not always.
Layshaft bearing question on 1970 750S
I have read all the dire warnngs about layshaft bearing failure to the point where i am starting to be paranoid about my rear wheel locking up and spelling the end of my short lived Norton ownership.There are no symptoms to date of it failing .i.e kickstart falling down . Ive read the gearbox...
www.accessnorton.com
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First sign is the kickstart lever moving back and hitting your leg on acceleration, at that point stop and get it trailered. Mine did that and 2 mins later I started to lose gears until left with only 4th. So very little warning and easily missed.
My MK3 had the same type factory Layshaft bearing as shown in L.A.B's post.
The kicker gave my leg a couple of bumps on acceleration so I changed the bearing to a roller.
The original bearing was still intact, lucky it gave a bit of warning before disintegrating.
That was with about 20,000 miles showing.
Glen
The kicker gave my leg a couple of bumps on acceleration so I changed the bearing to a roller.
The original bearing was still intact, lucky it gave a bit of warning before disintegrating.
That was with about 20,000 miles showing.
Glen
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Not all the Portuguese brass cages were FAG. Probably made in the same factory.
NickZ
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Of 5 gear boxes I have had apart, only the '73 850 had the Portuguese ball bearing, the exact one pictured above.. The others were 750s, and their layshaft ball bearings were British made. None had failed but all were replaced with roller bearings.
I did one while GB was in situ and the rest on the bench. I did not have an easy time refitting the new bearings in the shell while on the bike.
I did one while GB was in situ and the rest on the bench. I did not have an easy time refitting the new bearings in the shell while on the bike.
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Not always.
Layshaft bearing question on 1970 750S
I have read all the dire warnngs about layshaft bearing failure to the point where i am starting to be paranoid about my rear wheel locking up and spelling the end of my short lived Norton ownership.There are no symptoms to date of it failing .i.e kickstart falling down . Ive read the gearbox...
Other than some subdued noises while idling in neutral after kick starting earlier in the day (that stopped as soon as I played with the shift lever and never reoccurred) I had no warning.
Mine locked up as I shifted into 1st gear to make a left turn.
fiatfan
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Had a similar experience back in 78-79 or so, on my 1970 750 Roadster. Riding slowly in town, through a crossing, changed gear from 1:st to second and a light twist on the throttle - and a clonk and a rattle. No drive but the wheel didn´t lock up on me, so as I rolled on slowly I looked back and saw a long string of oil on the road..... The main shaft had snapped clean off, and the housing was split in two.
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Oui, c’était sur mon 750 de '72 neuf.
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C’est aussi mon point de vue. A ma connaissance, lorsqu’il y a une rupture dans ce roulement c’est souvent avec un pignon de sortie de boîte de vitesses de 22 dents, notamment sur le 850MK3, le remplacer par un 21 apportera plus de fiabilité aux roulements et à l’ensemble de la boîte de vitesses.
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A tic tic -tic -tic sound for a few hours , followed by the kicker lever moving up and down on it's own , followed by a catastrophic lockup of the rear wheel , followed by honkings of horns on my ass. 70 -750 . Go roller .
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If it was shifting good before the signs of failure, just buy a new bearing and replace it in the bike. Easy. Probably no need for full rebuild, but you could replace the 2 outer cover o-ring seals with x-rings if they leak.
baz
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You'd have to be really lucky if there were not other damage in that box
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Most of the reputable Norton dealers supply roller as replacement...
(and probably the disreputable ones, too!)
(and probably the disreputable ones, too!)
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