850 MkI identification?

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Tigernut

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I'm looking at an 850 MkI tomorrow. It has silver barrels (is this right?). It has been fitted with a single Mikuni carb with N&N filter - is this a good upgrade or is it a better idea to fit Premier concentrics (I've heard that the Mikunis can be troublesome to get right throughout the rev range).

To check that it is a MkI rather than a MkIA, is there a list of engine / frame numbers by year?

Finally, is there anything I ought to be looking at especially closely on a MkI 850? I've had a couple of 750s and a MkIII 850, but no experience with pre-MkIII 850s. Thanks in advance for any info and tips.
 
Tigernut said:
I'm looking at an 850 MkI tomorrow. It has silver barrels (is this right?).
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Yes.
Tigernut said:
To check that it is a MkI rather than a MkIA, is there a list of engine / frame numbers by year?
Click to expand...

If it's a Mk1 then it would have a serial number up to 307311 although Mk1A were produced from 306591 and I don't know if any Mk1s were also produced within the 306591-307311 range of serial numbers but a Mk1A model has a number of distinguishing features such as the black plastic airbox, black cap silencers (probably long-gone), 'across-the-frame' battery tray and Dzus fastening at the lower rear of the side cover, plus a few other minor details.
 
Tigernut said:
I'm looking at an 850 MkI tomorrow. It has silver barrels (is this right?). It has been fitted with a single Mikuni carb with N&N filter - is this a good upgrade or is it a better idea to fit Premier concentrics (I've heard that the Mikunis can be troublesome to get right throughout the rev range).

To check that it is a MkI rather than a MkIA, is there a list of engine / frame numbers by year?

Finally, is there anything I ought to be looking at especially closely on a MkI 850? I've had a couple of 750s and a MkIII 850, but no experience with pre-MkIII 850s. Thanks in advance for any info and tips.
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Silver barrels are correct.
 
Honest question, why do you care if it's a Mk1 or 1A? The differences are minimal and usually jettisoned (silencers and airbox) or just there to accommodate the air filter (battery tray as mentioned) and have no bearing on its performance or value either way?
On the single Mik, no problem with jetting, well documented and a good carb, but it does kill the top end performance. Both my recent 850s came with a single Mik, I converted the keeper back to twin amals because I like something left after 80 mph ish.
 
wavey_davey said:
Honest question, why do you care if it's a Mk1 or 1A? The differences are minimal and usually jettisoned (silencers and airbox) or just there to accommodate the air filter (battery tray as mentioned) and have no bearing on its performance or value either way?
On the single Mik, no problem with jetting, well documented and a good carb, but it does kill the top end performance. Both my recent 850s came with a single Mik, I converted the keeper back to twin amals because I like something left after 80 mph ish.
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Honest answer - I'm not really sure! I just had the idea that as it was advertised as a MkI, if I could be sure it is (or find that it isn't), it might give a clue to the sellers level of knowledge.

There seems no point in the Mikuni conversion if it has such a drastic effect on performance. One of the main reasons for liking Commandos is their superb performance. So, that makes maybe £500 worth of difference to the price, to cover a pair of standard adapters, a pair of Premier carbs and an air filter (though I suppose someone might buy the Mikuni kit, if they're as ignorant as I was about them until I read your reply)
 
L.A.B. said:
Yes.


If it's a Mk1 then it would have a serial number up to 307311 although Mk1A were produced from 306591 and I don't know if any Mk1s were also produced within the 306591-307311 range of serial numbers but a Mk1A model has a number of distinguishing features such as the black plastic airbox, black cap silencers (probably long-gone), 'across-the-frame' battery tray and Dzus fastening at the lower rear of the side cover, plus a few other minor details.
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Thanks LAB. The number is within the right range, so it is a MkI.
 
Tigernut said:
Honest answer - I'm not really sure! I just had the idea that as it was advertised as a MkI, if I could be sure it is (or find that it isn't), it might give a clue to the sellers level of knowledge.

There seems no point in the Mikuni conversion if it has such a drastic effect on performance. One of the main reasons for liking Commandos is their superb performance. So, that makes maybe £500 worth of difference to the price, to cover a pair of standard adapters, a pair of Premier carbs and an air filter (though I suppose someone might buy the Mikuni kit, if they're as ignorant as I was about them until I read your reply)
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The Mikuni is a nice carb, high quality and well made. They flow very well too.

The issue with the single Mik on a Commando has more to do with lack of space for a well designed manifold. Even the 36mm Mik I had just ran out of steam at around 5,000rpm.

If most of your riding is going to be below that, then it’s actually a good mod (high quality carb, light throttle action, no carb balancing to do, etc). But if you enjoy using the upper rev range when accelerating through the gears, it probably isn’t really what you’re looking for.
 
I have a single Mikuni on a 750. Did some work to manifold to improve flow. It runs Very well, better bottom end, and is very streetable.. I would not run out and buy Amals until other possible quirks are worked out. Not all Nortons are race bikes.
 
mean gene said:
I have a single Mikuni on a 750. Did some work to manifold to improve flow. It runs Very well, better bottom end, and is very streetable.. I would not run out and buy Amals until other possible quirks are worked out. Not all Nortons are race bikes.
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Strange to mention race bikes when no one else has !
 
Sorry Eddie they do call me mean Gene, Everyone rides differently, some have to have 'race' engines and never race. Some have stock bike and race to work! I enjoy riding my Norton's I'm not afraid to 'blow the carbon out' but I don't shift at 9000 every time. If I'm going to race I'll borrow my son's 1290 KTM!!!
 
Quite right.

But no one was talking about racing… or doing 9,000rpm…

I thought my final paragraph was very fair. If most riding is below 5,000 the Mik is a fine modification. But if you enjoy accelerating through the gears using the upper rev range then it won’t be what you‘re looking for.

You certainly do not need to be any kind of racer to enjoy taking Commando above 5,000…
 
Thanks for the info everyone. Unfortunately, my van's cambelt slipped and I need to spend what would have been Norton money on that (or another vehicle). It looked like a very nice one too...
 
Fast Eddie said:
Quite right.

But no one was talking about racing… or doing 9,000rpm…

I thought my final paragraph was very fair. If most riding is below 5,000 the Mik is a fine modification. But if you enjoy accelerating through the gears using the upper rev range then it won’t be what you‘re looking for.

You certainly do not need to be any kind of racer to enjoy taking Commando above 5,000…
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6,000rpm is a nice round figure on a commando
 
Fast Eddie said:
Between 4,000 and 6,000 is the FUN ZONE for me at least !
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I'm often above 5 grand but don't usually stray above 6500
There's not any more power up there anyway
And the most I have revved it is 7500 when I was setting the carburettor up
 
For those into this tangent,

Since this is a way out there tangent to the initial thread question, thankfully not caused by me, I'll widen it a little (then you can call it my fault :) ).

Considering all stock with a valve train in good shape, what do you consider the redline and max rpm to be for a 750? For an 850? And, what you do consider to be the best shift point for max acceleration on each?
 
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