1974 Commando 850 Barn Find

Starting a thread to keep track of my most recent build and put some questions to the site.

I accidentally purchased this 1974 Commando last Thanksgiving after throwing out a lowball offer to a Facebook marketplace seller based on some blurry photos and a video of the bike running. When I came to take a look, it was much worse than expected and I halved my initial offer fully expecting him to tell me to eat shit. However, he'd already had a few buyers balk at the condition so I ended up being the lucky one who finally had the lowball accepted. All in the bike cost me 2k.

As you can see the bike was very literally found in a barn. The odometer says ~5k miles and as I get into it I think that accurate. The plate shows it was last registered in 82'. While the seller had a video of it running and riding, he said something about the transmission was off and that it would no longer fire.

Since picking it up, I've essentially stripped it down to the frame to take inventory and begin cleaning everything up. Because of the condition, I'm trying to get this into riding condition with replacing as little as possible and only cleaning/derusting parts. This will not be a restoration and the finished product will be cosmetically rough, but clean and running well. Probably going to throw in an electronic ignition and a reg/rec I have laying around from a previous project, but otherwise leaving it the way it is.

So, first question, what are folks opinions on reringing/hosing/boring/ignoring cylinders? I pulled the barrels today and found them mostly in good conditions, with some discoloration but nothing you can feel with a fingernail except for this one vertical scratch. The pistons also look great and are original B range.

My thought was to have it honed and drop in new rings, but is that discouraged on these engines?


Photo of good side


And the bad side showing the scratch that can catch a nail.

looks like a good deal. I paid a grand for a1970 commando in much worse condition. not sure about the scratches but I would like a perfect bore if it were mine.

A light hone won’t do any harm if it makes you feel better, but even that is not really ‘needed’.

If the mileage is genuine I would not replace the rings personally… they’re just nicely bedded in.

Hammerski said:

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Was this bike in VT?

Hammerski said:

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Nice. The engine no is less than 150 off my bike. It will have been built late August 1974. See the roll on the bottom edge of the front guard. Genuine but you won't see it on any modern reproduction.

It's a valuable original example because for example while it's clearly a Mk2 not a Mk2 A it displays some of the features that some insist define an A variety. For example the notch in the rear chain guard for the inspection hole in the rear brake plate. It will also have the frost plugs on the end of the swinging arm spindle.

NPeteN said:

Was this bike in VT?

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Yes, still is too

I spoke with the seller as well, pretty sure I was next in line behind you. I'd say you did well for 2k.

ABSOLUTE GOOD DEAL, PERIOD! 50-year-old diamond in the rough.

Do the full refurbishing after a thorough clean & de-grease. Replace any knackered bits, leave the rest alone!

Very nice, will be a very sturdy regular ride if maintained per the service section, in the order it's presented.

How long has it been sitting exposed as pictured?

Lineslinger said:

How long has it been sitting exposed as pictured?

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No clue, but probably less than a year. Its in a dry storage unit now. There's a fair bit of rust but nothing crazy. Most of the Chrome seems intact except for the right size footrest and the exhaust crossover tube. I suspect the bottom of the oil tank sprung a leak because the rear of the engine back is coated in oil, which seems to have protected most of those parts from any rust. I haven't pulled the tires yet but I'm optimistic about the rims.

johnm said:

Nice. The engine no is less than 150 off my bike. It will have been built late August 1974. See the roll on the bottom edge of the front guard. Genuine but you won't see it on any modern reproduction.

It's a valuable original example because for example while it's clearly a Mk2 not a Mk2 A it displaces some of the features that some insist define an A variety. For example the notch in the rear chain guard for the inspection hole in the rear brake plate. It will also have the frost plugs on the end of the swinging arm spindle.

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Interesting, I noticed the frost plugs were different but didn't know about the rest. The other difference I've noted is the tank mounts seem similar to the Mk3 rather than the part book section on the mk2.

I would have just cleaned the carbs, change oil, check static time and try to get running. That bike is highly original and looks like it would have run with very little work. Original green spark plug wires too. Resist the urge to tear it all apart.

johnm said:

Nice. The engine no is less than 150 off my bike. It will have been built late August 1974. See the roll on the bottom edge of the front guard. Genuine but you won't see it on any modern reproduction.

It's a valuable original example because for example while it's clearly a Mk2 not a Mk2 A it displays some of the features that some insist define an A variety. For example the notch in the rear chain guard for the inspection hole in the rear brake plate. It will also have the frost plugs on the end of the swinging arm spindle.

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Mine is 319416. 25 before this one.

elefantrider said:

I would have just cleaned the carbs, change oil, check static time and try to get running. That bike is highly original and looks like it would have run with very little work. Original green spark plug wires too. Resist the urge to tear it all apart.

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Yeah, the previous owner had it running so I'm sure it wouldn't take much, but then what's the point? The front brake was full of rust, cables fraying apart, speedo cable broken, isolastics sagging, valve seats speckled with carbon or rust, trans full of what appears to be chocolate milkeshake, oil everywhere from an unidentified leak(s), and a dozen other problems. To actually have a bike capable and trustworthy enough to ride serious miles, I think its easier to just tear it down to the frame, clean everything, and put it back together. My opinion is that its better to have something that functions as good as possible, rather than keeping it as original as possible.

Interesting point on the green wires, I didn't give them a second look when I saw replacements were only a few dollars. I dug them out of a box today and they cleaned up well, I'll keep them on if they still work.

elefantrider said:

I would have just cleaned the carbs, change oil, check static time and try to get running. That bike is highly original and looks like it would have run with very little work. Original green spark plug wires too. Resist the urge to tear it all apart.

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I too see a survivor. Due diligence inspection prior to getting it running. Then repair as needed. Brakes. Obviously.
Tires. Clearly want to be able ride it like a MOTORCYCLE.

I did exactly this on my H2 barn find thread.
I rode it HARD for a couple thousand miles.
The transmission succombed to what I now know is a pattern failure. So, split the cases to repair the transmission... and on down the rabbit hole.

But, some people can't bear to even LOOK at, never mind enjoy an old war horse with some rust pits, or burned oil stains.

Personal preference.

Enjoy the trip, whatever you choose.

Pulled the pistons and found time to properly measure the bores today. Everything is currently within a half thou of the listed spec for the B grade bore. I think I'll leave the piston and bores as is, but try to clean up the carbon deposits on the tops.

Question, in the decarbonizing section of the manual is the passage below. What specifically does the emphasized part mean? Are they referring to the top or side of the piston?
"DO NOT remove the thin ring of carbon round the top of each cylinder bore and leave also a ring of carbon around the edge of each piston crown"

2nd question, the below photo is the exact orientation and sequence of the cam followers as they came out. The two on the drive side appear to be the same, while the timing side are a mirror image. I'm assuming someone has been in here before me, but maybe a factory error? Is this a concern? wear pattern looks fine.



3rd Question
Any recommendations for protecting crazed paint? So far I've just cleaned it with soap/water and lightly applied a light cleaner wax. I'm avoiding buffing so that I don't remove anything or damage the stripes. The sides seem fine, but the top is rough enough that I'm worried it will start to flake off with use.

Hammerski said:

2nd question, the below photo is the exact orientation and sequence of the cam followers as they came out. The two on the drive side appear to be the same, while the timing side are a mirror image. I'm assuming someone has been in here before me, but maybe a factory error? Is this a concern? wear pattern looks fine.

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The ones you've marked drive have a "V" (bevel) showing. That "V" goes forward. I'm assuming you mean that you're looking from the perspective of behind the cylinders. If so, the drive side was in backwards and the timing side was in correct. In any case, the "V" goes forward on both sides.

marshg246 said:

The ones you've marked drive have a "V" (bevel) showing. That "V" goes forward. I'm assuming you mean that you're looking from the perspective of behind the cylinders. If so, the drive side was in backwards and the timing side was in correct. In any case, the "V" goes forward on both sides.

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If your moving them about then may be a good idea to reface the surface rather than running them against a different cam partially worth.