Commando Frame Serial Number

Hello, I have recently purchased a 1970 Commando fastback. The engine has the 20M3S/ prefix, but the frame begins with QINVAAA

I was wondering whether anyone can tell me the significance of the QINVAAA frames. I realize that this is probably not the original frame, however I am more interested in the history of the frame and whether it would be a 750 or 850 frame since I've read that 750 top and bottom yokes should not be fitted to an 850 frame for fear of high speed handling issues.

Thanks everyone for your time.

TL

70FASTBACK said:

I was wondering whether anyone can tell me the significance of the QINVAAA frames.

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Welcome TL,

I've never heard of that "QINVAAA" prefix? Does the actual number match the engine and gearbox numbers, and where exactly is it stamped?

70FASTBACK said:

I realize that this is probably not the original frame, however I am more interested in the history of the frame and whether it would be a 750 or 850 frame since I've read that 750 top and bottom yokes should not be fitted to an 850 frame for fear of high speed handling issues.

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Frame identification

The very earliest 750 Commando frames didn't have the 1" bracing tube running below the main spine tube to the headstock, and the fuel tank brackets are fixed to the front down tubes instead of the 1" tube. If you have that sort of frame, then you should seriously consider replacing it with one that has the bracing tube?
For 1971, the frame lower cross member was moved forward from its original position under the gearbox and it lost its main stand mounting lugs, the main stand from then-on was bolted to the engine cradle.

850 model (from '73) frames had their part numbers stamped on the front face of the left-hand fuel tank mounting bracket, so check if there's a number there? The number can easily be obscured by paint or corrosion as the stamps are small faint digits, so are easily missed? I'm not sure if the '73 750 frames had their part numbers stamped in that location or not? However the '73 750 frame part number was 063709, the '73 850 frame part was 064140.

850 MkII frames had extended inner shock mounting plates, the part number is 065404, and the 850 MkIII frame is 065632. The 850 MkIII frame is easily identifiable as it has a mounting plate on the left hand side of the seat loop for the MkIII hinged seat and different shock plates to the earier frames. Some late 850 MkIIAs also had MkIII frames, but not the hinged seat, apparently. The majority of 850 frames also had an additional frame number stamped alongside the ID plate, many 850 frames were made from metric tubing so have a 60mm O/D spine tube diameter instead of 2-1/4" (approx. 57mm). If yours is a '71-'73 750 or early '73 850 frame and there are no visible part numbers etc. apart from checking the headstock angle it could be difficult to distinguish between the two frame types, unless anybody else knows of another way to identify them?

LAB,

If a guy had one of the rare non braced Commando frames that's going to become a collector's item. That would be a struggle for me whether to weld in a brace which could be removed later or to run a late frame and keep the old one.

Cookie said:

If a guy had one of the rare non braced Commando frames that's going to become a collector's item. That would be a struggle for me whether to weld in a brace which could be removed later or to run a late frame and keep the old one.

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Hi Cookie,

If a guy had one of the early frames, he should replace. That frame wasn't safe due to potential cracking and Norton recalled them replacing with the braced version. I already found I'm not a collector - dropped a '63 Electra in a dumpster once (where they belong) and sold a '74 JPN because it's the most uncomfortable motorcycle I've ridden and they belong in someone's collection.

To the original question of QINVAAA frame - not a clue. If stamped on the frame...interesting relic. As asked already are there numbers in the frame ID that match the engine number?

David

I guess you're not up all night over matching numbers then?

illf8ed said:

and sold a '74 JPN because it's the most uncomfortable motorcycle I've ridden and they belong in someone's collection.

David

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My fastback was born a JPN until fire turned all the plastic, rubber and fibeglass to dust and everything that could melt at low enough temperature like the carbs to metal drops, the previous owner also said it was horrendous to ride and I thought I was committing a crime to get it on the road with another dress :lol: :lol: :lol:

Jean

But that does come under the banner of saving it. The JPN stuff is all cosmetic isn't it?

JPN (Arctic Snow Frog) is not only all cometic, it rattles. Had to keep stuffing pieces of foam rubber between the fiberglass and metal parts.

Commando frame numbers are easily changed with a new number plate and some number punches...and four new rivets. So changing that recalled frame to a safer one shouldn't stop anyone.

Cookie,

Noticed you're in the bay area. Are you going on the Mt Hamilton ride with the NCNOC tomorrow? www.nortonclub.com

David

Unfortunately I'm on duty with Caltrain tomorrow. I can't go very far from the tracks, especially with Bay to Breakers. Work gets in the way of many a good time, but I'm happy to still have a job.
I won't even get a phone call usually unless there is an accident.

Hello TL,
I have a Ducati that had a frame replaced due to cracking around the steering head. When I went to register the bike all hell broke loose because the new frame didn't have a frame number. Anyway to cut a long story short, my frame had to have a surroget number stamped into it. The number they use has QINV------- , Q for Queensland, INV for investigation, then other numbers following.
Maybe this is what your QINVAAA is all about?
Regards Graeme.

Thanks Graeme. It is a Queensland bike, so that explains it. Best regards, TL

Though will a serial "number" like that you may have been "framed" >

My frame (1968) was one of the infamous widow makers. I wanted to keep the original number on the frame so modified it with the 1" lower tube welded in.

When I stripped it I found the right down tube almost cracked right through. Only 17000 MLS on it. And looks to be about right.

Don't know if I have destroyed a piece of Norton history..... But at least now I can ride it without worry if my frame is going to stay together.

D