crank case reassembly

Information relating to the Matchless G80 or AJS Model 18 500cc Heavyweight.
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crank case reassembly

Postby cfaber » Wed Sep 26, 2018 4:13 am

Does anyone have an assembly guide / tool descriptions for reassembly of the big end? Specifically pressing / pulling the crank back on the duel set of ball bearings?

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Re: crank case reassembly

Postby SPRIDDLER » Wed Sep 26, 2018 8:21 am

Not quite sure what you mean by pulling the crank back on the dual set of ball bearings? but some big end replacement info here:

http://archives.jampot.dk/technical/Gen ... ctions.pdf

and

Page 35 onward.......

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

There's more in the comprehensive F Neill Workshop Manuals in Christians Archive but it takes a bit of plodding through and the pages are rotated so you need to turn the computer screen 90 degrees :(
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Re: crank case reassembly

Postby Pharisee » Wed Sep 26, 2018 8:38 am

cfaber wrote:Does anyone have an assembly guide / tool descriptions for reassembly of the big end? Specifically pressing / pulling the crank back on the duel set of ball bearings?


Are you referring to assembling the two crankshaft main bearings rather than the 'big end'? This is the way I did it...
The two new ball races were placed on a baking tray and put into the oven at 200°C. The crankshaft was supported on wooden blocks on the table outside. The first hot ball race was dropped over the drive side axle and down to the locating shoulder. The washer and spacer that go between the two bearings were dropped on next, followed by the second hot bearing. No persuasion needed, they just dropped into position easily. The drive side half of the crankcase was heated in the oven to 200°C, the bearings on the crankshaft had cooled down so it was simply a case of dropping the crankcase half over the bearings. It dropped on with a satisfying 'ding' and that was that... drive side main bearings installed. No bashing, banging or pulling required.

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Re: crank case reassembly

Postby Big Pete » Wed Sep 26, 2018 9:43 am

Lovely job, loads of mechanical sympathy there :D :D
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Re: crank case reassembly

Postby clive » Wed Sep 26, 2018 12:23 pm

Should the bearings need to be heated to drop onto crankshaft? There are different grades of fit for bearings and I would have thought the bearings that need heating to fit to the crankshaft are too tight. The crankshaft should be a sliding fit in the bearings, at least all the bottom ends I have worked with are like that. If you have to heat the bearings to fit them presumably you are going to have to heat the the flywheels, conrod, crankshafts and one half of the crankcase to remove it.

In my experience you need to heat the crankcases to fit both bearings and before sliding the crankshaft into the bearings ensure that the washers between the bearings are properly lined up.
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Re: crank case reassembly

Postby SPRIDDLER » Wed Sep 26, 2018 1:39 pm

clive wrote:In my experience you need to heat the crankcases to fit both bearings and before sliding the crankshaft into the bearings ensure that the washers between the bearings are properly lined up.

That's how I've always done it too, also.


Heat the crankcase til it spits back when you spit on it.

And for afterwards, cook a rice pud on the top shelf.
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Re: crank case reassembly

Postby Pharisee » Wed Sep 26, 2018 7:07 pm

clive wrote:Should the bearings need to be heated to drop onto crankshaft? There are different grades of fit for bearings and I would have thought the bearings that need heating to fit to the crankshaft are too tight. The crankshaft should be a sliding fit in the bearings, at least all the bottom ends I have worked with are like that. If you have to heat the bearings to fit them presumably you are going to have to heat the the flywheels, conrod, crankshafts and one half of the crankcase to remove it.




It was a brand drive side axle (from Andrew Engineering) and brand new bearings (from the club spares). They were not a 'slide' fit. I could probably installed them by putting a length of pipe over the axle and tapping them on with a hammer, but I prefer to warm them up and install them without the need for brutality.


clive wrote:In my experience you need to heat the crankcases to fit both bearings and before sliding the crankshaft into the bearings ensure that the washers between the bearings are properly lined up.


That's exactly why I installed the bearings onto the drive side axle first. All the components are lined up correctly for installing into the crankcase half.

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Re: crank case reassembly

Postby SPRIDDLER » Wed Sep 26, 2018 7:19 pm

Each to his own, eh, John?
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Re: crank case reassembly

Postby spookefoote1956 » Wed Sep 26, 2018 7:27 pm

Crankcase in't th'oven, bearings in't freezer. Mind your fingers and always use oven gloves.
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Re: crank case reassembly

Postby clive » Wed Sep 26, 2018 7:38 pm

I think I might have tried polishing the new driveside axle to get a sliding fit. If you have to disassemble the crankcase how are you intending to get it apart except by heating the whole thing up?
clive
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