Compound fracture of the Crankcase. Pt.3.

Well guys and gals I've finally got her apart... Nasty business.! I think there may have been drink or drugs or both involved in the recent rebuild of this engine. Here's what I found....
Both inner timing cover seals (camshaft and crank) were sitting at an angle. The spring inside each seal had come adrift. There was no cir clip.
Camshaft sprocket nut was loose.
When we split the cases we saw damage to the Camshaft lobe and the Cam Key was sheared off.
We found many pieces of metal that was once a Crankshaft Stud Nut.! Yes a nut had obviously been left loose.
It flew around inside and pitted most things in general, then after splitting the front of the Crankcase, found its way between the Flywheel and the bottom of the bore liners which squased that section of liner, leaving a protrusion which then scored one piston then on to the Camshaft and I think this is when it got broken up between the Cam and the Cam well, and a piece went between the Cam and the Follower which broke the Follower and in turn bent the corresponding valve.
All repairable, that's the best I can come up with. Other than Buyer beware.!! Smooth talking sales persons don't make the best Mechanics.
Anyhow, she goes back together with.. The crankcase oil scavenge mod, GP 's Reedvalve breather,new pistons etc etc... Keep on keeping on. Bye for now.. AC. P.S. Photos coming.

That's the spirit ! It's always nice to be able to reconstruct a cause and to find that it wasn't a design defect but poor assembly.

There's a fair case for saying that any secondhand Commando ought to be immediately dismantled for inspection, simply for peace of mind.

+1 on "that's the spirit ! Are you repairing and using those cases ? I've got a lot better set of 850 cases I'll be listing on fleabay soon. Just curious, cheers.

Thanks for the support. I intend to bolt the cases together for welding, and hopefully all goes well. How many $$$ for a set of cases ? I may be looking for a 2S cam as well but haven't got that far yet. Perhaps a new one might be the go. Decisions, decisions... AC.

After you have had them welded, lap the two halves together with fine valve lapping paste. This will ensure they are mated up properly & won't leak.

Thats looks a very easy repair.............you dont need to bother with bolting cases together, or lapping paste! But it would be a good plan to take them to a welder who knows what they are doing, and has some sort of oven to put some heat into the case before welding, and then to let it cool slowly.

I'd want $200 for a set of 1974 850 cases, plus whatever the shipping costs. (They're already cleaned too ) I'll be listing them on ebay this week with a starting bid of $200, no reserve. Would rather sell them to someone here on the forum though ... and avoid the ebay fees.

Thanks NTB... My motor is 72. 750, Slitely different I believe...AC.

Oh my my, its cases like that than can make one feel like a real mechanic, with tool boxes full of new words and combo's, for increased self respect, after wards.

Cases can take a lot of punching and welding and fit and seal pretty good. Its welds near the seams that require brutal beating back in shape. Pretty hard to lap the cases with the dowel in and the lip in the way. I take a hammer to it to mostly punch back then file- grind basic contour. The welder will have to melt real deep and over lots more area that the visible damage, so be prepared for lasting scar. It helps to have the barrel mounted pretty tight and also a big ass heat source. I prefer a tank top pancake heater I can dismount to keep most of the case oil vaporizing hot while welder does his thing, Welder will appreciated the fast high heat if ya lug you own heat in there instead of his wimpy torch to try to big to even temp in half and hour or so, sheeze.