AJS & Matchless Owners Club

Hey Experts,

With some help from the forum, I have managed to do everything by my self on my G12 and G3 and the last thing I would like to learn and accomplish is to disassemble and reassamble the crankshaft of my 350. I have a hydraulic press, lathe, and all other equipment that could possibly be needed.

Can somone explain to me how to do it and what to look out for ? I am specialy concerned about the alignment at the end, since I cant figure out how this is possibly done after the flywheel has been pressed on to the crankpin. I have seen people hammer them into alignment. But this was only on smaller cranks where the force of a hammer would be enough to twist one flywheel half on the crankpin. But I believe that our 350 are to tightly fitted for them to turn on the crank pin, am I right ?

So how does it work ? I have seen the description in the manual but it doesent give me enough confidence for such a sketchy task.

Thanks a lot.

Yves

This might help... not AMC but the principle is the same.

Just watched the video... I've never done it but it doesn't look too difficult at all, happen you have a fly press and a lathe with a big enough swing over the bed. I reckon that I could fabricate a fixture to do the alignment between centres but at the moment, all my crankshaft assemblies are running happily in motorbikes.
Could anyone tell me the diameter of the flywheels and the overall distance between the ends of the mainshafts, please?
Cheers, John

You'll need a min swing of 240mm or 9 3/4" dia over the bed and as for centres if it's a cush drive single I guess 400 mm or 16" to give a little adjustment, maybe less but not much.

ajscomboman wrote: ↑Fri Sep 17, 2021 11:14 am You'll need a min swing of 240mm or 9 3/4" dia over the bed and as for centres if it's a cush drive single I guess 400 mm or 16" to give a little adjustment, maybe less but not much.

Thank 'ee kindly, sir... Too big for my little Myford. I'll fabricate a fixture when I've finished the latest project. I think I can make it adjustable for length without too much trouble.
John

I recall assisting in doing this with an incredibly robust jig. A steel base in the region of 3" thick, with a pair of very large diameter (3" ?) posts set in it at right angles, a massive drawbar centred between the flywheels & the posts and nut with a crescent shaped slider to wind up against the flywheels.

No lathe, no measurement and it worked well enough for his racing AJS.

Johnny B

Hi All,
Thanks for your replies.
John, thanks for the video !
From all the videos which I have already seen about this topic, this is the most helping one. I must have missed this one.
I feel confident, enough to try it. Although I am still a bit insecure about my method of measurement, since i am not measuring between centers but on V-Blocks. Which makes it tougher to determine which side is high and which one is low. Between centers, the high side reads high on the gauge. On V-Blocks, I figured out, that I have to messure outside of the V-Blocks, meaning to the end of the spindles, with the V block further towards the midldle of the crankshaft. If I do so, the reading are the oposite. Which means the high sided flywheel will read low on the gauge. Which makes sense if you think about it, or make a drawing of it

So I guess Ill give it a go, and see where I end up…

Cheers Yves

The result:

It worked out just fine. I ended up measuring between centers. Although I am sure its also possible on V-Blocks. But with V-Blocks its not so obvious which side is the high side then.

It took about 5 hits with a 2,5kg copper hammer and I am now down to 2/100mm which has its low point on both sides vertically above the crankpin. Which means the flywheels are aligned but not parallel to each other. So tomorrow I will spread the flywheels away from each other on the opposite side of the crankpin, using two crowbars stuck in between the flywheels, pushing outwards and that will probably be it. I have seen that done in a nother video.

So to whom ever wants to try to assemble a crankshaft. Go ahead. I find it not that difficult.

Thanks for the help guys.

Yves