What is it?

Hi,
I've just acquired a '74 850 Commando. It's a bit of a project, but looks complete albeit with a Mikuni carb instead of the Amals. I'd like to know if it's a Mk1, Mk2 or Mk2A, what are the distinguishing features that will help me identify which it is. The engine No is 308884 and the date on the plate shows 10/73. It has a RH10 head.

My plan is to build a JPN replica with Mag wheels and three disks. I need to source clip-on's and rear-sets but already have all the JPN bodywork.

I'd appreciate any input.

Ian
SoCal

Commando 850 Apr 1973 300000 First 850
" Sept 1973 306591 MK IA 850
" Jan 1974 307311 Mk II and IIA 850
" Feb 1975 F12001 Frame number MK III

See this post for II/IIa - mk2a-commando-t18847.html. There was another post too, but i lost it...

Siver barrels is the sign of a Mk1 850 - but could have been painted black since.

The plastic airbox is a sign of a Mk1A or Mk2A.
Would have also have the black cap mufflers.

At that date and number, its almost on the changeover between all of them.
They made some of them at the same time too, so its not a simple date or number changeover.

Think the yankee ones got the triple pass mufflers , for the dreaded REGULATIONS .

Hi,
It does have steel side panels, black cylinder, replacement silencers.

Any other distinguishing features?

Ian

ianashdown said:

Any other distinguishing features?

Click to expand...

The black plastic airbox makes it a 1A or a 2A.
The LHS sidecover mounting is different with the plastic airbox too.

It is of course possible to change the whole (cosmetic) lot, the basic bikes underneath are all about the same.

There are a couple of other differences to look out for which aren't so easy for the PO to remove - the MkIIA got a different kickstart lever - I think it's longer, and with more clearance for the silencer, and they changed the 2nd gear ratio - no way to tell without counting teeth or measuring the ratios some other way. The battery tray is also different - Dzus fastener lug on LHS and the battery fits across the frame, not fore-aft.

I believe that the original JPNs were essentially Mk11As with black exhausts underneath the swoopy bodywork.

Let's see some photos!

I have a build date 1973 850. It's pretty typical commando and seems to still have the original exhausts. They have the welded tip and are very quite. They are pea shooters and not the black caps and has the normal ham can air cleaner. I've just never seen exhausts like it has. The bike only had 4k miles on it and appeared 100% original when I got it.

Did original pea shooters back in late 73 have a welded outlet tip and would they be very quiet? I've been thinking of shelving them and putting a proper set on so it just sounds better.

Rohan said:

ianashdown said:

Any other distinguishing features?

Click to expand...

The black plastic airbox makes it a 1A or a 2A.
The LHS sidecover mounting is different with the plastic airbox too.

It is of course possible to change the whole (cosmetic) lot, the basic bikes underneath are all about the same.

Click to expand...

The three MkIIIs I have owned or worked on ALL had the plastic airbox.

Probably the battery carrier is the hardest to change and best indication of a Mk2a. The dzus fastener bracket is at the top right of the carrier. Note the original gear lever for the JPN was a special reverse mounted deal that sticks out away from the gearbox more than normal. You end up with an inverted gear shift pattern.
Funny you mention replica of a JPN, which was a "replica" in itself of the real racer. Use lots of foam rubber insulation to get rid of the fiberglass rattles

http://i707.photobucket.com/albums/ww77 ... erJPN3.jpg

There are a lot of little differences between the 850 Mark I, Mark II/IIA's. Visually the Mark II/IIA's have a dust cover on the bottom of the instrument cups. They also have a black tail extension on the chain guard. The cylinder barrel is black on the Mark II/IIA's while the Mark I's are silver. However all of these things and more can be added or removed on the motorcycle which could make identifying the Mark series difficult. The one thing that is hard to change on these motorcycles is the frame. The Mark I's and the Mark II/IIA's each have a different frame part number. The only difference I know of between the frames is that the inboard shock mount bracket is longer than the outboard ones on the Mark II/IIA's while both shock mount brackets on the Mark I's are the same length. They extended the shock mount bracket on the later bikes to help support the rear frame loop.

The John Player Norton replica is basically a converted Mark IIA so to make an accurate replica of the replica you would need a Mark IIA. However, a Mark II can be converted to a Mark IIA. Among many other things, you will also need an 850 Mark III Z-Plate to mount the extra zener diode.

Hi,
I guess I should have said I'm thinking of building a John Player Norton Replica Replica!

I'm not trying to build something that claims to be a JPN at all. I'd original thought about building it on a Mk3, it's still a possibility, and then a acquired this recent one whatever it is. I plan to use Mag wheels, double discs at the front and a single disc at the rear, so no one will ever think it could be a real JPN . .

Ian