16M Engine - broken nearside crankshaft boss

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Tween69
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16M Engine - broken nearside crankshaft boss

Post by Tween69 »

I have a stand-alone 16M engine in good condition but have just noticed after years in my garage that the nearside crankcase boss around the end of the crankshaft has sheared off! Is this a common occurrence? Is there a ‘repair kit’ available or does one DIY? Is it just a flat disc with a hole for the shaft or does it have to seat an oil seal inside?
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clive
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Re: 16M Engine - broken nearside crankshaft boss

Post by clive »

It is not usual and I doubt there is a repair kit. I doubt that you will be able do a DIY repair as internally you should be seeing one of the two main bearings now. The boss is recessed to take this bearing. Externally it is stepped to take the inner primary chaincase and there are three bolt holes for securing it. I am inclined to think the rest of the motor is now spares unless you can get a matched pair of crankcases.
clive
if it ain't broke don't fix
Iron Head
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Re: 16M Engine - broken nearside crankshaft boss

Post by Iron Head »

Wonder if it was condensation that got behind the outer bearing race and froze in a hard winter and fractured the case through expansion?

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raffles
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Re: 16M Engine - broken nearside crankshaft boss

Post by raffles »

You wont need a pair of crankcases AMC sold them separately
. One of my own engines has a mismatched pair so for a stand
alone engine you could get away with just changing the drive
side crankcase and there are a lot around
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Triumph-Legend
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Re: 16M Engine - broken nearside crankshaft boss

Post by Triumph-Legend »

Tween69 wrote:I have a stand-alone 16M engine in good condition but have just noticed after years in my garage that the nearside crankcase boss around the end of the crankshaft has sheared off! Is this a common occurrence? Is there a ‘repair kit’ available or does one DIY? Is it just a flat disc with a hole for the shaft or does it have to seat an oil seal inside?
Very close but no cigar.
The raised boss that locates the inner primary chain case can become severely damaged by a wayward dynamo chain chewing away at the casting. another cause may be the fitting of incorrect length spacer behind the drive sprocket.

Can this be repaired? Of course it can. The method is to machine a new stepped disc and to machine the case section to accept the new part which is then located and welded in place, the case then machined to accept the outer crank bearing, and to drill and tap the three chain case securing fastners.

Don't waste an otherwise set of crank cases for a bit of repair work to bring them back to perfect working order. Send them along to T&L Emgineering. I'm sure they will be able to help. Probably a lot easier than putting together a pair of miss matched case halves.
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Plum
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Re: 16M Engine - broken nearside crankshaft boss

Post by Plum »

24BE939D-23B1-4AE8-A413-CEF963F9E2E4.jpeg
This happened to me but mine broke out when removing bearings.it was cracked before I started.now fully welded as can been seen in picture in oven if you you know the man for the job sorry about image size
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Triumph-Legend
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Re: 16M Engine - broken nearside crankshaft boss

Post by Triumph-Legend »

Nice pictures and repair.

Try that with your kwakersukihonda mate.

It's a sod when the Araldite melts init. :rofl:

I bet you cried when it fell to bits.

Not a problem sir. Lots of older machines do this.

Easy fix with JP weld.

Just file the case smooth, the bit that fell orf was probably not needed anyway.

Just use a dab of Bearing lock on the main bearing, jobs a good un.

The loose bit only locates the chain case anyway.

Now you know why there are so many old brit bikes around. The bloody things just won't die.

Can't think of any more just now. But feel free to offer your comments.
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Old Thumper
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Re: 16M Engine - broken nearside crankshaft boss

Post by Old Thumper »

I had something similar on mine when I set about restoring it. Having cleaned all the gunk and grime off, i found the bearing housing cracked.
I just got the workshops at work to weld it up for me and then spent a good couple of hours afterwards with a hand file and some wet & dry to shape it back to its original profile and it has been fine ever since. :)

Some before and after photos...
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