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Nightmare

Classic Norton Commando Motorcycles.

Nightmare

Postby gripper » Wed Feb 15, 2017 2:11 pm

Won’t need a helmet for a bit. I was starting the Norton on my rollers this afternoon and it wouldn’t start probably because one plug lead was off. Anyway after a prod of the kickstart there was no drive through the box and the clutch was all floppy. Going through the gears revealed a stoppage so I didn’t push it too far and thought that the kickstart pawl must have broken and was maybe jamming something. Took off the outer cover, nothing. took off the inner cover and forgot that you would normally have to undo the nut on the end of the mainshaft (which is under the clutch release mech.) Not necessary in my case because the mainshaft is now in two bits and second gear (mainshaft) has two teeth missing. (Well not missing because I found them in the bottom of the case.)
This is my theory that is all mine. starting on rollers in second gear has shock loaded the gears, breaking off one or two teeth, they had jammed the gearbox, deflecting the mainshaft far enough to snap it. BOLLOCKS Anybody want a set of start rollers? Cheap.

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Re: Nightmare

Postby auldblue » Wed Feb 15, 2017 2:24 pm

Is the gearbox shell damaged at all ,cos if it's not ,I think it's not as bad as it could have been. Still pretty shit though.

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Re: Nightmare

Postby gripper » Wed Feb 15, 2017 2:38 pm

Shell looks ok but totting up the cost of parts, it's going to be bread and dripping for a while :cry:

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Re: Nightmare

Postby grandpaul » Wed Feb 15, 2017 3:13 pm

There are ALWAYS people looking for starter rollers...
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Re: Nightmare

Postby auldblue » Wed Feb 15, 2017 3:38 pm

Has it not been started in a while, Was the clutch plates free or stuck together with gear oil ?

gripper wrote:Shell looks ok but totting up the cost of parts, it's going to be bread and dripping for a while :cry:


Good fortune on that one. It was porridge for me when my box popped.
And he sayeth The meek shall inherit the earth,
But it's roads belong to commando 750's
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Re: Nightmare

Postby ashman » Wed Feb 15, 2017 4:41 pm

The problem that caused that is starting it in 2nd gear, to much shock, when some low life theived my kick starter off my Norton back in late 1979 I couldn't get a new kicker at the time so had to clutch start it all the time, doing it in 2nd or 3rd gear all it did was to lock the back wheel, but clutch starting it in 4th was so easy but you had to be quick with the clutch lever when it fired up with out snuffing it, so if you fired it up in 4th gear on the rollers will put less strain on you gear box, a friend of mine starts his race Triton on rollers and he always does it in top gear, he learned a long time ago from a few breaks from starting in low gears, since doing it in top gear he hasn't broke nothing.

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Re: Nightmare

Postby kerinorton » Wed Feb 15, 2017 11:23 pm

Naughty. Naughty. The only way to crash start any engine is in the highest gear. Everyone now knows what happens when you disregard common sense. Shame.

Dereck
IF IT AINT BROKEN , DONT FIX IT.......71-750, 74-850

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Re: Nightmare

Postby splatt » Wed Feb 15, 2017 11:33 pm

Crap, hasn't been assembled with a mismatch of late and early second gears by any chance, mine was when I got it and the lay shaft snapped
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Re: Nightmare

Postby Rohan » Thu Feb 16, 2017 12:24 am

You don't say what year this is, but Nortons put out a bulletin at some point (early 850 ?), warning that the mainshaft should be checked for straightness.
The implication being that some weren't, and that they could snap.

Ain't old bikes fun....

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Re: Nightmare

Postby gripper » Thu Feb 16, 2017 3:49 am

Mainshaft second gear has an oil hole through it, the two teeth that went astray are either side of that hole. 1970 750 probably original shaft, I've only had it 42 years. I've always bump started in second gear but I suppose a higher gear would make sense

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Re: Nightmare

Postby gripper » Thu Feb 16, 2017 1:37 pm

The clutch was free before the start attempt and the gears are the correct 18:24 pairing. I notice that the break in the mainshaft is where there is an undercut, reducing the overall diameter. Mind you I wouldn't expect a full diameter to survive that sort of damage.
I'm wary of undercuts on shafts. In 1990 the tail rotor pitch change mechanism on my Puma chopper featured a splined shaft that was undercut where the splines ended. That reduced the diameter of the shaft wall and it let go at a most inopportune moment. (loss of tail rotor control is always inopportune) the resultant ditching in the English Channel was an experience to say the least. Still any landing you can walk away from, or in this case swim, is a good one.

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Re: Nightmare

Postby Matt Spencer » Fri Feb 17, 2017 6:08 am

They Do That ! ( dont ask how I know ) . Youve probably bent the layshaft , too .

Once people realised you waited untill the temperatures were up before standing on it .

BUt , if ' youve always ' bump started it in second gear ' , did you run / roll start it , in neutral AND shift into second . :twisted:

Cold Oil / baulkey shift . Forced ! .

Had someone ride mine with ex plod boots ( WW1 DR in NZ ! ) My delicate sensitivities were jarred on every graunched shift ,
whicxh was most of them .
The things these Triumph Riders do as a matter of course ! You can clutchless shift a Triumph , forcefully .

A Knorton , it is a matter of timing and dexterity , learnt by driving crash box tractors , Straight Cut truck boxes etc .

A toe on the shift , and itll go in when it wants to - delicately . Any More Force is force & forces it .
I recomend you equip yourself with winklepickers .
And check the Mainshaft output bearing housing .

:(

Dommie bits'll fit .
A new mainshaft in NZ was $ 80 in NZ about 81 , and they ( someone ) had one ' on the shelf ' . Wonder multiplication on price now . :(

Er , cool day And not using clutch , or even with the clutch , drag & cold oil may result in such uncalledfor consequences . As the large Boot forces gears out of kilter .
Check the Clutch Drum spins true on the bearing , too . :(
The Japanese response to ' styling ' , was to add more .
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Re: Nightmare

Postby gripper » Sat Feb 25, 2017 4:56 pm

Spot on Matt, bent layshaft 0.018" out

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Re: Nightmare

Postby acotrel » Mon Feb 27, 2017 1:33 pm

Matt
'Dommie bits'll fit .
A new mainshaft in NZ was $ 80 in NZ about 81 , and they ( someone ) had one ' on the shelf ' . Wonder multiplication on price now . :( '

The Commando mainshaft is about 6mm longer than the Dommie mainshaft.
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Re: Nightmare

Postby JimNH » Mon Feb 27, 2017 3:39 pm

gripper wrote: I'm wary of undercuts on shafts. In 1990 the tail rotor pitch change mechanism on my Puma chopper featured a splined shaft that was undercut where the splines ended. That reduced the diameter of the shaft wall and it let go at a most inopportune moment. (loss of tail rotor control is always inopportune) the resultant ditching in the English Channel was an experience to say the least. Still any landing you can walk away from, or in this case swim, is a good one.


Very low airspeed? Immediate AR?

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