350cc 16MS Crankshaft end float

Information relating to the Matchless G3 or AJS Model 16 350cc Heavyweight
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350cc 16MS Crankshaft end float

Postby velocette » Mon Jan 18, 2021 12:04 pm

Having had a new big end assembly fitted by Alpha for my 16ms, I find that on reassembly in the cases I have excessive end float on the crank. By drifting in the timing side bush slightly as recommended in the manual, I have managed to reduce this to approximately 1/8 inch. This seems very excessive as the manual quotes between 10 and 25 thou!

The original big end pin had snapped and may of exerted lateral forces on the main bearings during failure. The engine has not covered many miles since the main bearings were renewed and they appear to be in good condition. I would therefore ask whether anyone can provide guidance as follows.

1/ Given that once the shock absober drive shaft spring is fitted and tensioned, the shaft will be held against the drive side bearings thus eliminated any end float, so will this be a problem?

2/ I have read accounts of shims being fitted to eliminate excessive float, would this be the best method of resolving this problem situation.

3/ Any guidance on the cause of this problem and any remedial actions, would be much appreciated

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Re: 350cc 16MS Crankshaft end float

Postby SPRIDDLER » Mon Jan 18, 2021 1:56 pm

Neither your Profile nor post show the year. ;)
I've read a few manuals and I realise I'm old and the memory isn't great but I don't recall any ref to moving the t/s bush to adjust end float. I doubt that the bush would remain in that position as it relies on the flange to locate it laterally in the c/case and a dowel or peg to prevent it from turning. It's more usual to machine the bush to obtain clearance.
There should be two washers 'twixt the main bearings. The smaller is merely a spacer and the larger one as well as being a spacer also acts as an oil (mist) baffle.

See page 24 here ref end float:

http://archives.jampot.dk/book/Workshop ... dition.pdf

This is a '54 engine but I have a recollection :? that one of the washers wasn't needed/fitted in later engines. The Spares List for your year of engine will tell you.

Single spacer.JPG
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Re: 350cc 16MS Crankshaft end float

Postby velocette » Mon Jan 18, 2021 5:05 pm

Apologies Spriddler, mkissed off the obvious, the engine is 1956. The advice re. adjustment of end float by the timing side bush is contained in my copy of the original AMC workshop manual.

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Re: 350cc 16MS Crankshaft end float

Postby SPRIDDLER » Mon Jan 18, 2021 6:42 pm

Hmm, strange. The link I gave was for F Neill's manual - he was the AMC Service Manager.
His advice in the link is to adjust end float by machining the t/s bush or moving the outer race on later models.

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Re: 350cc 16MS Crankshaft end float

Postby velocette » Mon Jan 18, 2021 7:49 pm

Managed to find the image from the manual re. adjusting end float by moving timing side bush

AJS image.pdf
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Re: 350cc 16MS Crankshaft end float

Postby SPRIDDLER » Mon Jan 18, 2021 9:46 pm

velocette wrote:Managed to find the image from the manual re. adjusting end float by moving timing side bush


Well I never! I do now recall seeing that drawing showing how to measure end float but never paid attention to the bit showing the method of adjusting the end float by moving the bush. Every day's a school day, although I must be lucky as I've never had to reduce end float....or increase it.
I guess just knocking the t/s bush 'inwards' the small amount that you need will be fine if the manual says so just as long as it doesn't dislodge the bush locking peg/dowel inside the c/case.
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Re: 350cc 16MS Crankshaft end float

Postby velocette » Tue Jan 19, 2021 10:50 am

I have adjusted via the timing side bush, but movement of this is limited and I am still left with excessive end float and I am at a loss as to how to remedy this.

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Re: 350cc 16MS Crankshaft end float

Postby Greybeard » Tue Jan 19, 2021 11:30 am

I understood that moving the bush was for earlier engines only. The later ones with the flanged and pinned bushes should be shimmed with bronze washers (at least on the timing side - as the drive side shaft turns with the bearing a steel spacer could be ok there) according to the Ken Bryant's comprehensive and excellent article on rebuilding the H/W singles - the article is in the tech library.
I would also be checking that the conrod is still central having lost that much width of the crank. It may need to be shimmed both sides. Too much endfloat will increase the wear on the oil pump gear.
The shock absorber drive will help hold the crank tight against the drive side bearing but may still allow some 'bounce' against the spring pressure won't it? Not a problem with the later alternator ones as the crank is fixed by the rotor.

Steve

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Re: 350cc 16MS Crankshaft end float

Postby velocette » Tue Jan 19, 2021 11:55 am

Thanks Steve and your comments which are most helpful.
I have a copy of the Ken Bryant article which is the only document I have seen which mentions the use of shims to alleviate this problem.
With regard to moving the timing side bush this is referred to in the AMC workshop manual for the 56 models as show in my previous posting. However the movement available is minimal before the cut away fouls the oil pump, and not enough to resolve my problem.
I am coming to the conclusion that shims are perhaps the best way forward.

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Re: 350cc 16MS Crankshaft end float

Postby SPRIDDLER » Tue Jan 19, 2021 11:59 am

Greybeard wrote:I understood that moving the bush was for earlier engines only.


That's my understanding which is what prompted me to post the clip from the manual and ask the year of the engine.

End loading detailed.jpg


Unless the main ball race(s) can be adjusted I agree that shimming is the answer, keeping the conrod central, although I'm surprised that shimming is required.

It seems that there is some ambiguity/lack of clarity within the various manuals.
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Last edited by SPRIDDLER on Tue Jan 19, 2021 12:14 pm, edited 5 times in total.
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