New Crankshaft

Information relating to the Matchless G12 or AJS Model 31 650cc twin
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New Crankshaft

Postby RogerJ » Thu Aug 02, 2012 8:49 am

There is a photo of the casting of the new 650cc crankshaft in the photos section under Post-War Twin Parts.

This and another will be machined for the dynamo and alternator variant to be road tested - so on schedule (more or less...)

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New Crankshaft

Postby rex.webb » Fri Aug 03, 2012 8:46 am

Now its " Full Steam ahead " as they say !
Ride with CARE and LIVE LONG to ENJOY your Bikes .
(With a NEW CRANKSHAFT).
r w webb

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New Crankshaft

Postby Rob Harknett » Fri Aug 03, 2012 11:18 am

We would like to think so Rex, now tell FIVA and fill in the survey else there may be nowhere to steam ahead.

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New Crankshaft

Postby mdt-son » Sat Oct 06, 2012 12:00 pm

Hello Roger and eveyone who has ordered a new crankshaft or fancy having one,

it may be of interest to you knowing the following. I visited the ABSAF premises in July to discuss the renovation of my recently acquired '64 G12CSR engine. The proprietor Jan de Jong is a very experienced engineer who has manufactured parts for the BSA B33 Goldstar engines for years (actually he produces complete engines) and a few years back he also started to reproduce the G80CS engine, albeit using his own ideas, thus improving on the old design. Recenbtly, his interest has turned towards the G45 and G12 engines, for which very nice barrels are available now and I believe G45 inspired heads will follow.
Working on most british marques (e.g. Triumph), Jan has broad insight into engine design and his views are well worth listening to.

Anyway, being a mechanical engineer myself, we had a vivid discussion on the new crankshafts now being made. Jan pointed out one design flaw in the original design and one area which should be improved upon. The design flaw relates to the oilway drilling, which leaves a sludge trap inside the crank - a potential source of disaster due to ingress of contamination or even blockage. Jan suggests to deviate from the factory design by making the drillings as Triumph made them, i.e. with a direct path to the rod bearings. If this is not possible, tuned plugs should be used to ensure that no sludge traps can evolve. I think this modification can be realized at the new cranks at hardly any cost or technical consequence - please consider this proposal ASAP.
His second idea was to revert to G45 /early G9 center bearing size, as he thinks the bearing support, oil transfer and lateral location of the crank is much better in the intial design. Of course this modification requires the center web to be exchanged on later engines. Maybe the project team can make this an option? I for one would prefer to have my cranks (I have ordered two off) machined to G45 center bearing specifications.

Apologies for not presenting these ideas last month. However, with the main batch still in the foundry, I look forward to reading your comments. If we can have a better design, I think we can wait a little longer for the cranks?

Knut Sonsteby

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New Crankshaft

Postby 242017 » Sat Oct 06, 2012 1:39 pm

The BSAF man has a lot of weird ideas...non of which in his G80/G85cs engine seem to be of any benifit to anything..Everything for example is made to his design in millimeters...which means if it goes wrong nothing is going to fit...except his stuff
His engine from a motocross/racing engine is a waste of time...in a design way
Plus its an expensive waste of time around 8000 Euro

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New Crankshaft

Postby zwarts » Sat Oct 06, 2012 2:27 pm

I too visited Jan de Jong at ABSAF, in June this year. Whether you think his ideas are 'weird' (and is this not just another way of saying that he thinks for himself?) or not, he is a very skilled and knowledgeable engineer and produces some exquisite racing stuff. If you doubt this have a look at his website. I spent a very interesting morning with him discussing the AMC twin engine in which we agreed there is a lot of potential for further development. He has a first class manufacturing set-up and many ideas as to how to realise this potential and I think we will hear more about these in the future. Jan's ideas are far from pipe dreams. They are already transformed into metal.
Is the ABSAF stuff expensive? Compared to what? We are dealing with top quality, small batch production parts here and they are very similar in price to what you would pay for similar items if you were running a Manx or G50 today.
The day after my visit (and the prime reason for our trip to the Netherlands) we were competing in the local road races (the amazing 'Z-Z Races') and were able to see some of Jan's products in action. They did not disappoint!
Bob.

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New Crankshaft

Postby 242017 » Sat Oct 06, 2012 4:34 pm

But you cant mix his parts with Matchless parts, and his go "how well ???"...as compared to what?
Stuart Tongues Matchless??
If you want to make a reliable single that goes well and is compatable with any other Matchless spares
get in touch with the man who makes the spares for our club and plenty others...
The ABSAF man is barking up the wrong tree
And Im talking about a G80 motor...Not a G50 which he doesnt make...His prices are too high for what he makes and his castings are not as good as the original Matchless ones

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New Crankshaft

Postby GSAX1 » Sat Oct 06, 2012 7:38 pm

Where is the sludge trap you are talking about? As far as I can see the design is very sound. My own crank did not have any blockage after 50 years.


[url="http://www.ajs-matchless.com/pic_display.asp?id=258"]Pic of crank passageways.[/url]

Edited by - GSAX1 on 06 Oct 2012 7:39:56 PM

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New Crankshaft

Postby zwarts » Sat Oct 06, 2012 10:29 pm


Yes the ABSAF G85CS parts are not interchangeable with the originals, this is clear from the spec. If you have an original, this is a problem. If you don't, it isn't!
G85CS parts may well be obtainable elsewhere, I don't have one, so I wouldn't know. But I don't see too many listed in the club spares scheme (or elsewhere for that matter).
I agree, this is a G85CS pushrod engine, not a G50 - that's why it is not as expensive as a G50 engine.
If you consider the price too high for the specification of the engine and identical (or better) quality parts/engines are obtainable elsewhere, then that is your choice to make.
'Barking up the wrong tree'- in what context?
'Castings not as good as the original Matchless ones'- are they porous/rough/badly finished, or what? The ones I have seen were fine.
Bob.

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New Crankshaft

Postby 242017 » Sat Oct 06, 2012 10:56 pm

Strange I have in the last three months had an original motor for sale..as towards spares they are no problem to find for a norton oil pump motor..Nothing strange in that...
Absaf engine looks not very well compared to an original one
His theory of the changes he has made doesnt make any sense...
I have known riders buying his engine parts then having to spend a lot of money to make them competitive for racing..and the owner was dutch
so no problem with not understanding anything...Why then did you compare his prices to a G50???
They have nothing to do with each other
Im at a loss to understand why he makes a G80 engine that no parts are interchangable and is only at 500cc
As I stated "weird thinking"
I wonder why he bothered???

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