850 barrels on a 750 motor case? Does it work?

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As I recall, the cases must be machined to take the larger cylinder. It's not an easy swap, but do-able. More interesting is the crankcases on this bike are at least from a '72 (no timed camshaft breather) model, so I wonder how they have a 1971 series engine number!!
That was my question, not that I plan on buying or such, but something isn't quite correct about the bike, or....he's not being accurate about the info he is giving....that could be too. Hard to figure how the numbers could match.

Guess it will be the problem of the fellow who buys it...... :wink:
This bike was at the Perth Scotland Autojumble on sunday and the Lanark Scotland autojumble in Jan so its been doing the rounds. The engine number is in the 150000 range so is a 71 allegedly, the barrel and head is 850 and the primary is Electic start. The frame engine numbers match but its a bitsa in my eyes, nicely done but a bitsa none the less.
This brings up an interesting point....I've had time now to reconsider. Here we are, and I started this discussion......zeroing in on the fact that this bike has been kind of "fiddled" with, and, in reality...bet not a one of us has a bike that in some way or form hasn't also had in essence, the same thing done to it.

Take at a minimum, the tail lights, fenders, exhausts and seats into account, and there won't be too many machines that are all from the same year and model that they started out to be. Fact of life when it comes to cycles, maybe not with the newer Jap machines, but when our British machines were newer, the fad of the cafe racer changed almost every machine England ever built. Just read through the threads in our forum, and you will see that this fad hasn't died, but that it maybe has gotten even stronger amongst us. Not too many of us are trying to put our machines back to original specs.....God....that would mean the old crappy isolastics, and the head steady from hell, to mention a few of the original parts that have gone the way of the dustbin. Just consider the list of those who have put new front Jap/Italien brake kits on thier bikes.....

So....I guess we might be doing the fellow an injustice here in getting all picky about whether it is original or not. Maybe if the machine is legal and the work has been well done.....we should just try and see it for what it may indeed be..a souped up 71... :wink:

My first post on the forum. I hope you don't mind me barging in on a controversial one.

What this chap has is something different from a machine with a few earlier or later bits on.

The instrument panel looks ex-Interplod to me and that may be a clue to the bike's origins. Apart from the front drum and the "S" type side panel, I can't see many bits that shout out 750

I have a set of Mk111 crank-cases which have been used with earlier chaincases and it was necessary to re-drill the cases for the earlier inner chaincase fixing bolts which do not line up with the Mk111 alternator mounting studs and fit a substantial adaptor plate. The whole system is completely different. Mk111 cranks have more widely spaced mains and the chaincase therefore sits "deeper" on the cases in order to retain the chain line. Mk111 cranks are longer as well because of the starter sprag which means that the alternator rotor sits further out.

I really doubt if conversion in the other direction is practicable and suspect a complete Mk111 engine unit. Unfortunately, I haven't got enough loose bits handy to check if it looks possible. Primary chain adjustment is also impossible with the later cases. Has he got a Mk111 tensioner system? I can just understand someone using the Mk111 set up if they wanted left-hand shift but this bike doesn't have that.

My vote is very definitely for a "Bitsa"
I have to agree with 79X100 (7,900 for short!) Given that Commandos have a data plate on the frame (unstamped replacements readily available) instead of stamped numbers and that you occasionally see unstamped cases for sale, our bikes are particularly easy to 'counterfeit'. My observation is that Commandos also have the number stamped on the top of the gearbox along the top mounting boss. This may be another way of assessing originality.
Actually Dave it's 79x100 = 490 but it could just as easily have been 73x89 x2 or 77x89 x2

For the sake of honesty, I probably should also mention that my early 1972 pre-combat 750 now has a Norvil disc instead of a drum, unstamped 750 MkV crankcases and un unstamped 850 Mk111 type gearbox shell.

My 850 Mk111 now has a replacement Andover frame following severe accident damage. It currently has it's original crankcases back in but has a second hand gearbox shell (it is Mk 111 though) oh, and a 750 airfilter and battery tray just to confuse casual observers along with the ground-off and re-welded starter boss on the primary chaincase.

I am a great fan of "pick 'n mix" Commandos and am always open about what I've modified
Gosh.....we got that one started, didn't we.

The machine seemed a bit strange to me , and that is why I started the thread in the first place, but I wouldn't suggest that something was for certain not on the up and up with it.... We all know the machines can be fiddled with, one of my commandos has numbers stamped in, from the dealer, and the other didn't have any until the German inspection got a hold of it. Nice long non-Norton number in the steering head now, right next to the data plate with the "real" number in it. Data plate alone wasn't enough to satisfy them that it wasn't stolen, even with me having the original title and all documentation for 30 years...
But...if we are honest...we all know a couple pop rivets will make a bike be what it never was. All this doesn't mean htough, that the machine in question isn't just what he says it is....a porked up 71....

PS...gearbox numbers are on mine, at least, matching the motor and frame...unless someone steals your motor.....I will get into that story sometime in my blog.... :wink:
Sorry if I've overstepped the mark but it is not so much the bike itself that puzzled me but the tone of the seller's answers.

Someone took the time to very diplomatically suggest that it would be sensible to be certain of his facts and his response seems to me at least to indicate that he wasn't prepared to check his information.

I seem to remember that as long ago as 1977, "Motorcycle Mechanics" ran an article suggesting that the phrase caveat emptor only came about because "someone in the used chariot bazzar was selling second-hand Commandos" I wouldn't disagree with that but I do feel that sellers have a certain responsibility to answer direct questions.

Less cynical minds than myself might also wonder why German ebay was used.

I must admit, I have a habit of winding up sellers at Autojumbles as well. Maybe I'm just twisted :evil:
Not trying to change your mind about this fine piece of British workmanship....but rather just pointing out that there are more than one ways to look at this and I decided not to call the kettle black if you get my drift.
The fact that the seller doesn't seem to be really interested in the "facts" about the bike, and the way he answered guess who's inquiry as to his decription....were to be expected. The man is afer all, trying to sell the machine, and who wants to be reminded that there might be a question or two about it...he would just see this inquiry as a threat and actually, I'm surprised he didn't pull the question off the ebay page.
Incidently, the bike was listed in the UK and I just found it because I have "norton" set up as an ebay automatic search and e-mail option. The German on the page is simply the translation of the original english the seller filled in when he entered the info into the page.
This all might just be immaterial anyway, in the long run, as, if the action continues in the manner it is now going, other bidders will be scared off by the questions and he will never get the minimum price he has set on it...so it won't sell......this time. We will see.
Still question if all his info is accurate though, and the old saying still has it's place in our vocabulary...."let the buyer beware".... :wink:
Maybe he is just naive. He certainly hasn't done himself any favours by adding the Q&As to his auction.

My apologies as well for thinking he had listed overseas. I also saw it first on ebay.de but I think that is because I just look at parts on ebay.uk Do you know why the ebay search system is so poor even if the search should be Worldwide ? For Norton parts I regularly look at .de, .com and .aus and usually find items which didn't appear earlier.

The strange thing is that if he made a virtue of the mods, he could make it sound quite attractive. All the plusses of the strongest bottom end fitted in the quick steering 750 frame with the classic - looking drum brake plus zero road tax in the UK.

I reckon it's up to about the value of it's parts now. If he wants more, he's going to have to engage in some salesmanship.

Commandos on ebay quite often fail to reach their reserves. Are they falling out of fashion ?
It was a dealer that had it for sale on his stall at both autojumbles, he hass had it for at least 5 months so well knows what it is. Didn't look at the frame plate but the engine number looked factory stamped is same as on mine.
As you may have noticed..I have gone a bit through my entries and cleaned them up.
Those of us that have commented on this subject might be wise to also re-check and if appropriate, edit what we have written here, with the thought that we might not like to see any of it used against us in some way that might prove expensive. This is after all, an open forum and how do we know if the person involved isn't chalking up points.....think what you may....but I figure it might be smart. We all know what we were talking about, and we have expressed ourselves, but now I just see no further reason to leave myself open to possible retaliation...

That little voice inside my head doesn't work often...but it did this time.... Lets call it quits on this.....:wink:
Point taken,

As a newcomer, I should have judged the style of the forum a little more subtly before jumping in. I too have gone through my posts and, I hope corrected anything that drifts away from pure technical comment.

I have tried not to affect the sense of any subsequent posts; My apologies if this is the case.
kommando said:
Didn't look at the frame plate but the engine number looked factory stamped is same as on mine.

Did you happen to notice the area around the tacho drive ? The Mk111 850 is machined flat there rather than having the cast "well" which always collects oil and water :)
Dear Chaps, I see no reason for undue circumspection, nothing anybody has said on this thread has been specifically accusatory and we have merely been making factual observations based on our collective knowledge and experience. All of us are at least theoretically potential 'consumers' of this product and have a right to question the veracity of the vendor's claims, given that we have identified discrepancies between what we observe in the pictures and what we (probably as anoraks) know about our subject. I have only been a contributor to (and beneficiary of) this forum for a short while and have found the content to be informative, useful and amusing and hope that we don't sanitise it or succumb to the 'political correctness disease' that seems to be sweeping some parts of the world. Having said that good luck to anybody trying to nail me in Hong Kong for expressing my opinion on this site!
I actually think the fellow we trashed a short while ago for trying to sell that abomination of a Commando chopper on e-bay USA has a better case against us for psychological damage, mental cruelty and a newly developed case of 'anoraknophobia'. However I think we are safe as I am confident that I can run faster carrying my various basket-cases than he can ride on that disgraceful machine.
By the way for the record I wish to state that I use the word 'chaps' in a non-judgemental, non-gender-specific, caring sort of a way.
Well he lives in Scotland, we don't dive for the lawyers as easy as you do :lol: , well not yet anyway :evil:

I just see this as a debate as to whether this bit is a nicely modded bike or a mismash of parts eg bitsa.

In the UK 72 and earlier bikes can run on the roads with no road tax, 73 and later pay £80 a year, so the only way to get an 850 norton roadtax free is to have a 72 or earlier frame and add or modify the engine to 850. That may be the reason for the initial conversion.

I didn't look at the tacho drive area, I quickly realised it was a bitsa and moved on to his much more normal and nicer looking T140E.
Ron & co....
There is a rather simple fact that caused me to edit my post on this subject.....as the wife tells me; "you can think what you want, but you better not say it if you can't prove it".

I've had a long life of opening my mouth and saying the first thing that came to my head and I've had too often to retract it. I was often wrong. Saying just what you think, rarely has the result of proving anything to anybody else other than how stupid you were to actually say it. The old saying still goes. "Better to be quiet and have everyone think you are an idiot, than to open your mouth, and confirm it."
This thread was hovering just above the point when either myself or one of the other contributors would have let loose with just exactly the statement that would have clarified and spelled out what we were perhaps all thinking might actually be the case in this. And that....would have given some guy with a white wig...just enough to put a cramp in someone's style.

This has nothing to do with political correctness, but rather with the fact that all of us would like to have the same right to be judged by "facts" and not by "presumption". I doubt the fellow involved would have wasted too much time, if one of us had let slip the "S" word. My intuition still tells me what it did, but as I can't prove it, so it just isn't worth the risk to say it. As pointed out...what we all did to that fellow with the chopper....you hit the nail on the head...but that stayed with opinions as to the persons' taste. It didn't, as I recollect, drift in the potentially dangerous direction that this thread was heading towards. Better stick to facts...there are enough factual discrepancies about the item, to keep us busy for awhile yet.
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