Mk 3 Crankcase front casting

trident sam · Oct 27, 2012

I've got 2 Mk 3 Commandos , just recently buying my second, and there is a sort of diamond shaped "protrusion" at the front of the case below the iso mounting. What is it for ? my other earlier bike doesn't have it.
sam

L.A.B. · Oct 27, 2012

It's one of those odd Commando conundrums. Some 850 Mk.3 castings have it, most apparently do not. There has been a certain amount of speculation about what its original purpose was intended to be.

trident sam · Oct 27, 2012

Thanks,
Any idea what that speculation is ? I nearly didn't buy the bike when I noticed it, but it looked like it was original to the bike.
sam

Rohan · Oct 27, 2012

Any pics anywhere to see what this looks like ?

Hobot · Oct 27, 2012

Maybe is was damage to the casting mold, maybe by sabotage?

bwolfie · Oct 27, 2012

Maybe it was preparation for adding the balance piston.

Torontonian · Oct 27, 2012

We need a picture. Never seen it , mine does not have it. A diamond in the rough ?

trident sam · Oct 28, 2012

I will try and get my mate to post a picture this week , I'm crap with computers
sam

L.A.B. · Oct 28, 2012

Photos courtesy of 'Bigbossmonty', who sent me these pictures of a Commando engine he'd bought.

This particular crankcase protrusion appears to have what looks like a blanking plate attached by two bolts, other protrusions seem to be just a plain casting.

trident sam · Oct 28, 2012

Mine is just a plain casting.

850cmndo · Oct 28, 2012

Up here we might slip a block heater in there.

Hobot · Oct 28, 2012

Sure looks like the rear Combat breather boss was put on wrong side of that case half, but its not a fully formed version of the Combat so mystery deepens.

lcrken · Oct 28, 2012

Thanks for posting the picture. I've never seen one like it, and I've had several MK3 engines. It's clearly a factory feature, and I'd love to know what it's for.

Ken

slimslowslider · Oct 28, 2012

looks a bit like the timing plug feature as on BSA A50/A65 models, where I think it is used to fix the crank (slotted to this purpose) at TDC:

Chris · Oct 28, 2012

Hi Lab

I remember reading about this but cant remember where. In Roadholder?
Article was about extra blobs cast in cases & what they were for.

Chris

Mk 3 Crankcase front casting

trident sam

L.A.B.

Moderator

trident sam

Rohan

Hobot

bwolfie

Torontonian

trident sam

L.A.B.

Moderator

trident sam

850cmndo

Hobot

lcrken

slimslowslider

Chris

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