AJS 350 crankcase repair

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AJS 350 crankcase repair

Postby Mac01 » Fri Sep 14, 2018 8:02 pm

Hi all, my 1948 AJS 350 is about to be stripped for a repair to the upper oil pipe union on the right hand crankcase.

At some point in its history, someone has managed to strip the thread in the crankcase and split the case itself. The oil pipe union was held in place with solidified red hermatite ! Great !


Does anyone know of a suitable engineering firm, in Kent or East Sussex, who could carry out such a repair, properly ?

Personal recommendation is always welcome.


Failing that, does anyone have a spare right hand crankcase, in good condition, for sale ?

The engine number is, 4916M 10138B (the bike being registered on 31/12/1948)


Many thanks.


Mac.

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Re: AJS 350 crankcase repair

Postby Rob Harknett » Fri Sep 14, 2018 8:22 pm

Sadly a common fault of PO's is tightening too much. Is it just cracked and closes when the union is removed. If so give it a good clean, put the union back till it starts to open up fill with araldite remove union. Damaged union seats are usually cause of leaks here, so a PO probably tried to cure the leak by tightening the union. So watch those S/H pipes you pick up. I sort of grind them in the clean them up. No impressed ? See if you can see a leak or crack on my repair done 1987. Been ok now for 31 years. Did the similar repair to Rocker box and gearbox on my 1936 AJS 1986. Still OK. I though sooner or later I would have strip parts bare to get a proper job done. But as the years rolled by with no mishaps, that's how its gonna stay now. You may get a lot more probs and work swapping cases.

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Re: AJS 350 crankcase repair

Postby Mick D » Sat Sep 15, 2018 7:24 am

Hi

If you decide to give Rob's solution a go and want a bit more peace of mind I'd suggest you use Metalset A4, it's an aviation approved structural epoxy adhesive ideal for bonding aluminium. It's not cheap but over the years that I have used it I've never seen it fail.

Regards Mick

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Re: AJS 350 crankcase repair

Postby Andy51 » Sat Sep 15, 2018 8:28 am

Hi Mac, I had a similar problem with my 18S. I had badly chewed thread in the crankcase for the oil pipe union, and while I had a new crankpin put in by a brilliant engineer, the late Malcolm Saggers, he fixed the oil pipe union. He took the thread up a size and made a new union to screw in the crankcase which had a parallel outer end, and the rubber oil hose is a push fit over this outer end, with a hose clip for insurance. You could take a similar approach by having a new union made up, and fitting it in with Araldite/Metalset, etc, to secure and seal it. It will now be in there permanently, and you can detach the pipe without disturbing the joint or putting any strain on it. The new fitting is just a piece of hex bar with a length appropriately threaded (BSP thread, don't know size), a hex length for spannering, and a parallel length to fit the pipe (check bore) - any machine shop could do this. Make sure you thoroughly clean the thread in the crankcase, as oil will have seeped into every pore and crack over the years, to ensure adhesive sticks. Hope this helps, Andy

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Re: AJS 350 crankcase repair

Postby Rob Harknett » Sat Sep 15, 2018 12:14 pm

Mick D wrote:Hi

If you decide to give Rob's solution a go and want a bit more peace of mind I'd suggest you use Metalset A4, it's an aviation approved structural epoxy adhesive ideal for bonding aluminium. It's not cheap but over the years that I have used it I've never seen it fail.

Regards Mick

I did not consider Araldite until an engineer mate told me. " My 1928 Morris Bullnose car head has cracked between the valve seats. I am getting repaired using ??? company to repair it with aradite " I Thought if its good enough for a head repair, it would be a simple job to repair my cracked crank case. I cannot recall what type I used, but whatever it was 30+ years have passed and still OK. Also my 36 AJS gearbox and rocker box as previously mentioned. There is quite a blob on the gearbox repair, I sometimes touch up with silver paint. Although oily dirt hides it OK

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Re: AJS 350 crankcase repair

Postby Mac01 » Sat Sep 15, 2018 12:49 pm

Thank you all very much.
Some interesting suggestions there.
I was speaking with an old friend re the problem and he was suggesting a Time sert repair. I used to use these often, some years ago for thread repairs.


Thanks again.


Mac.

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Re: AJS 350 crankcase repair

Postby Dixter » Sat Sep 15, 2018 4:27 pm

Mac, the only benefit of inserting a Helicoil, or similar is to retain the original union nut. A very small benefit once the extremely high cost of a special thread insert is factored in. Threading to a larger size and turning up a new union is a good path. You might find the YouTube video in the link below helpful.

https://youtu.be/JAZe3Iznp90

Best wishes,
Dick Casey
Dick Casey
The RideNut

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Re: AJS 350 crankcase repair

Postby Mick D » Sat Sep 15, 2018 4:53 pm

Hi Dick

Nice workshop you have there, however for someone getting a third party to carry out the work I reckon your logic is flawed.

A helicoil insert is less than a pound and it's use would halve the time taken for the repair and also allow the original one piece tank to engine oil line to be retained.

Both solutions will, of course, require the crack in the casting to be addressed and getting a professional engineering works to repair with epoxy may also be an issue.

Regards Mick

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Re: AJS 350 crankcase repair

Postby GOLDSTAR » Tue Sep 18, 2018 8:05 am

gosh! what an excellent and informative video, if just for the engineering skills shown, if mine were half as good I would be ecstatic, in response to the metal oil pipe usage, all my pipes are hydraulic flexibles with home made connections to the tank via caravan gas fittings. kind regards

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Re: AJS 350 crankcase repair

Postby clanger9 » Tue Sep 18, 2018 11:01 am

It's well worth checking out Dick Casey's other YouTube videos. They're brilliant!
1966 AJS Model 14 250 CSR "cafe racer"
1993 Ducati 750SS

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