750 Commando Question (Serial #s)

Looking to buy a 750 Commando with the following numbers:

The frame and transmission numbers are 203807
The engine number is 209058

The bike looks exactly like a Roadster, but the Norvil site says that the frame corresponds to a 1972 Interstate. Is this correct or am I misreading something. Also, am I correct in concluding that the engine is not original to the frame (or is there some obscure Norton lore associated with this). Can't wait to join the Norton club!!!

By the way, if any owners are looking to sell a 1972-1974 750/850 in SoCal, let me know (pypgb AT mindspring.com). I am looking for a solid runner, need not be a garage queen, that I can ride to work. Moving to Cali on July 10th. Thanks!

Keith

You cannot tell the original model from the serial number. The engine in your bike was apparently replaced at some time. Interestingly it was replaced with one of the same model year. Your serial number is within the series of the Combat builds. If the breather comes off the back of the crankcase rather than the end of the cam and the cylinder head is stamped with a "C" on the top of the head, you have Combat motor.

Hmmm.. here's a close-up photo of the motor. Looks to me like the breather (that black hose?) comes off the back of the motor, no?

Link to Photo of Motor

It's hard to tell from that side, but I don't see the hose running down the primary case, so it does indicate it is a Combat series motor. Visible modifications are the single Mikuni carburetor and late style Roadster seat.

After buying the bike ( it looks good) you will may need to add a few things. A few ha. We always add a breather to these models. you just drill and tap a hole in the spot were the old mag use to mount. Add a 90 degree fitting for a 3/8 hose and pipe it up to the oil tank. Also do this to the older cam breather models as well. Many add a one way valve to the hose on the way up to the tank as well. This mod helps with many problems.

Here is the view from the other side -- any help ID'ing the bike is appreciated:

View 2

If it is a Combat, should I steer clear? I would like to have a decent daily rider. Not averse to tearing into the motor down the road, but I want to ride a little first! Thanks!

ID the bike

Looks like a late '72 combat engine. Probably had superblend main bearings installed at Andover from new. The "magneto position" is cast closed, typical for late '72 and later crankcases. The seat and gas tank look to be from a '74 850 - good modification. The rear reflector is from pre '71. It's something of a bitsa, but not bad.

Don't stear clear just because it's a combat. The weaknesses are likely already taken care if it's still running. It depends on what you want to do with your Commando. If performance the combat is a good choice. If touring, get an 850 Interstate.

Thanks for the observations -- I definitely would not have picked up on the bitsa "conversions." Any idea what would be a fair price for this bike, with 28K showing on the odometer?

Again, if anybody in SoCal has a lead on a known quantity Commando, please drop me a line.

Thx!

As far as I know, all Combat and later detuned 750 models had the rear crankcase breather, even the 1973 models. The '73 850 models had a pipe from the back of the timing case (photo 2 shows this bike doesn't have that), the '73 750's did not use that 850 breather arrangement. So the presence of the rear c/case breather doesn't really indicate that it is a Combat model.

The Norvil info could be incomplete (surprisingly!), as some US Combat models were, I am sure, made as Roadsters (perhaps whoever wrote the info was thinking more of the UK Combats which were generally built as Interstate models?).

The 'C' stamped on the head is the best guide, but in 72 you normally specified the Combat to get the disc brake as it was a fixed pairing in the options. The other giveaway is a smaller fin gap between the top barrel fin and the bottom head fin as to get the higer compression Norton planed 60 thou off the head, yours looks like the gap is smaller but can't be 100% certain.

comat ID

Since the machine in question has the "combat breather" and is from the '72 model year, it is a combat engine. The '73 model year had the combat crankcases, but is diferentiated from the '72 combat by serial numbers that started at 220xxx. Most Commandos sold in the US during the '72 year had combat engines, we demanded the performance.

Regarding "some sold in the US were roadster"? Most of them were roadsters. The Interstate with combat engine didn't come out until several months into the '72 calendar year, while roadsters commenced production in Sept '71. One of the early combat roadsters, 201123, was my first Norton. I bought it in May '73 with 300 miles on the odometer.

Re: comat ID

illf8ed said:

Since the machine in question has the "combat breather" and is from the '72 model year, it is a combat engine.

Click to expand...

But not all '72 models were built as Combat versions?

And probably not all US models either, as far as I am aware the '72 Hi-Rider was not built in Combat form?
Neither were the majority of '72 Fastbacks (OK, so you probably didn't get many of them in the US) but these still had as far as I know what you describe as the "Combat breather".
As you say "*Most* Commandos sold in the US during the '72 year had Combat engines.."

So on the evidence of it having a rear crankcase breather and being from the '72 model year production doesn't necessarily 100% identify it as Combat.

As this particular bike seems to have some non-original parts fitted then even the presence of the disc brake does not positively identify it as a Combat?

I've put in a request to the owner to look for a "C" stamped on the front of the head -- this should resolve the question, but since it is very difficult to prove a negative, can somebody with a Combat motor tell me precisely where on the head this mark should be?

The crankcases without the blanking plate behind the timing cover are what I have always known as MkV 750 cases and were fitted to the 1973 750s which had long black clock-holders and the square tail light. 1971 20M3S motors had camshaft breathers. All the 200000 series 750 motors than had them down at the back, regardless of engine type and the 850 had them behind the timing cover. I don't believe that there is such a thing as a "Combat breather"

The bike looks like a normal 1972 machine which has later crankcases stamped with a 1972 number. This is perhaps not surprising because I don't believe that the earlier cases continued in production once the modified version was available. My early 1972 750 (200530 - front drum and low comp) also has MkV cases. I think that it just indicates a period blow-up. Nowadays, most would look for cases from the same year but at the time, I think the best option was a new set .

The MkV cases are stronger but lost the sump strainer which was not such a good idea.

The rear light looks OK to me and has indicator lugs although the nice thick rimmed side reflectors look earlier. 1970 bikes had silver light unit.

The 1972 brochure states that Combat and Front Disc were available on Roadster and Interstate so presumably just the good old Fastback was left out. I have read somewhere that the first Combats were Interstates but I can't find the source at the moment.

Bearing in mind that this motor has been apart, it probably has Superblends but there's only one way to be sure.

nomadwarmachine said:

I've put in a request to the owner to look for a "C" stamped on the front of the head -- this should resolve the question,

Click to expand...

All that would actually *prove* is that the bike has a Combat cylinder head! And tells nothing about the engine internals, and if the engine has been rebuilt (with Superblends etc.?)

Cylinder head info: http://atlanticgreen.com/nhth.htm

79x100 said:

The MkV cases are stronger but lost the sump strainer which was not such a good idea.

Click to expand...

'72 model cases didn't have it either (as far as I know) although possibly your early (pre-Combat) cases did?

Sounds like the only way to know is to have the bike blow up, or to take the motor apart. Not sure that I really want to risk it, since I need to this bike to get to work in LA for 7 weeks.

'72 model cases didn't have it either (as far as I know) although possibly your early (pre-Combat) cases did?[/quote]

You're quite right of course, I should have checked in the parts book. To be honest, I didn't know my 750 when she had her original cases. She had been violated by others before I met her :shock:

I just had an idea that the one disadvantage with my MkV cases was that lack of a strainer. I think that Tim Steven's words about the steel cam bush lugs going through the oil pump made a big impression on me all those years ago.

You are a Noccer with a copy of the "Service Notes" aren't you L.A.B. ?

I have just noticed the new post by nomadwarmachine - I really wouldn't worry too much. If the mains are not noisy now, they are most unlikely to fail over a period of seven weeks. What sort of mileage are you talking about? You probably have a safer option than for instance a late Mk111 850 which might still have it's factory-fitted soft cam.

If you're thinking of buying and the price seems OK, take someone along who knows Commando engines for a good listen and ideally a test-ride. If it runs well, it's probably a good one that has been cared for.

You should be aware though that if you intend to do a reasonable mileage, at some point you're going to have to have a look inside. Am I the only person who ever takes things apart to see why they're going so well ? :roll:

The chances are that it was a Combat spec bike but the 'blow-up' happaned many years ago, and that the engine may have been rebuilt with replacement cases, Supeblends etc. and stamped (although maybe not stamped to match the frame that it is now fitted to?) so it may be OK?

79x100 said:

You are a Noccer with a copy of the "Service Notes" aren't you L.A.B. ?

Click to expand...

Yes! And a few other things! But still happy to learn more.

Okay, cards on the table.

My plan is to fly into Los Angeles, where I will be working for 7 weeks, on July 7th. I hope to have a bike sorted out IN ADVANCE, so that I only have to rent the cage for a few days. Once I have the Commando in my possession, I intend to ride it to work for those weeks and do any necessary maintenance/upgrades over the weekends.

Now get ready for the fun part....

When the summer is over, I intend to ride the Norton 3,000 miles to Boston, MA, where I attend school. I have a running bet with my best friend that I will not need to UHaul it a single mile, and I have done this trip on a 30-year old machine before, so I am physically/mentally/emotionally prepared to do it again. Just need to be sure I am mechanically prepared.

So basically, I am relying on the kindness of forum strangers and my own research abilities to help identify a likely bike BEFORE I fly out to California. I found this bike and spoke to the owner -- he seems like a decent fellow, and is asking $3800 for this machine, at the moment. He tells me that it runs well and, rubber notwithstanding, doesn't see a problem with riding it over the summer. What say ye? Deal or no deal?

Thats a California price alright or maybe evilbay price. I would think a simular bike in the midwest would run 2500 to maybe three grand. It is not a mark three you know.