Welded crankcase

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Aug 7, 2004
In two weeks time I’m going on a trip to England (From Denmark that is) to have a closer look at a “matching numbers” Mk3 Commando (with the intention to buy). From pictures I have received, it looks like the crankcase has been welded at some point. Should I be concerned about this, or will it be as good as new (if repair is carried out correctly)? Will this weld decrease the value of the bike, and will it be possible to re-do the repair, so it won’t be visible as it is now?
Please see photo on this link: http://groups.msn.com/Brit-Fe-Pics/weld ... hotoID=189
Any suggestions will be appreciated. :)

You have a tough decision here. My concern would not be so much about the weld quality as it would be about the crankcase itself. No doubt this engine threw a rod a some point, damaging the crankcase - thus the weld repair.

The extent of crankcase damage may have been severe, requiring more welding than you can see in the picture. And more welding means more heat, which could possibly distort the crankcase.

However, if the crankcase vertical seam and the cylinder base gasket joint appear well sealed and there are no visible gaps or misalignment, chances are the cases are ok.

I personally think the '75 Commando is great bike, with its left-hand shift and steel gas tank.

If the price is right buy it - they're not making anymore of these great classics!


Hi Niels,

The welded case is a great concern. Find out the details of what happenned and what was done to fix all the damage. If abuse is suspected there could well be damage to other components such as the gearbox, primary and swingarm. If the price is good and you know what you're in for this could still be an acceptable deal. There is no real shortage of Commandos yet, so weigh the cost of repairs against the cost of a perfect machine.
I bought a Combat from e-bay about a year ago. It too had a welded case but at the top of the cradle on the left side. It being a Comat, I assumed it let loose and then was repaired. The local wrench told me this was a common crack due to loose cradle bolts, common to ALL Commandos, not to worry.
This crack is in the arc around the front motor mount and may be caused by the same problem, loose bolts. If this is the owner who had it welded, he may not know why it cracked, it just cracked. If the motor hadn't let loose, I would accept his answer. HOWEVER, I am no expert.
Overall condition and price would determine the purchase for me.
Good Luck.

Excellent point!

A cracked case does not necessarily mean that a piston rod has been thrown.


case crack


By cradle do you mean the rear engine mounting plate?
Yes. My weld is at the left upper gusset where it blends with the casing.
I also want to clarify the conversation I had was only with the rear mounts.
We did not discuss the front mounts. I was just thinking it was a possibility.
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