first choice 74 or 75 gearbox

first short intro: i bought a new 1974 norton 850 in 1975, rode it eventually converted to dunstall, sold it, am now back looking to scratch the itch, and want some advice:

search for the perfect 1974 or 1975,

i am comfortable with the rh shift, but were there any improvements from 74 MkII to Mk III in 75 to make it a standout better gearbox. from all the searching i have done i haven't found anything to show an improvement. would it be easy to convert a LH shift gearbox back to RH shift by just deleting a few bits?

I love my RH gear change, so smooth, most moden bikes don't shift so sweet as my Norton.

Ashley

ashman said:

I love my RH gear change, so smooth, most moden bikes don't shift so sweet as my Norton.

Ashley

Click to expand...

Same here. As one magazine article succinctly put it "It's like shifting a box full of warm butter". To the best of my knowledge, they have the same internals. Before taking that at face value, search http://www.oldbritts.com/ob_main.html for different tranny part numbers (kickstart shaft, for starters) and this site for much conversation about MkII versus MkIII. Where's Phil when you need him?

Nathan

Other than the second gear set all Commando gearboxes are the same. The exception is the '75 shell is a one year only part. That alone leads me to go with '74 gearbox over '75 - more numbers of parts available.

Converting the LH shift box to RH shift is easy and can be done using standard parts - You'd need inner and outer covers plus parts of the selector mechanism therein.

Most of the work, if you're converting a Mk3 (with disc brake on the right hand side of the bike) will be creating a brake operating system that you're happy with in terms of looks and performance.

I've had both. My Mark 111 did not shift as nice as the RH shift.
My feeling is it has to do with the extended linkage running through the back side.
It wasn't bad, I would buy another one.
It's just not the same 'buttery' smooth shift.

Also, the Mark 111 has a more complex primary.
The only real advantage to a Mark 111, is the E start.
And that needs to be fettled.

Most 73 and 74 850 use the same casting as the MKIII. All are better than the earlier 750 ones. More beef around the bearing pockets.
The MKIII has 2 machining processes that make it unique for LH shift and neutral switch. But yes, the extra MKIII linkage is prone to being more mechanically sloppy. Especially if the bike has been "tipped" on it's side and the shifter boss in the outer primary often cracks internally. It's more common than most people are aware of.
The last AN case I bought (many years ago from Ole Britts) was a newer improved version...with even MORE beef around the bearing pockets than the original 73, 74, 75 version.

MichaelB said:

I've had both. My Mark 111 did not shift as nice as the RH shift.
My feeling is it has to do with the extended linkage running through the back side.
It wasn't bad, I would buy another one.
It's just not the same 'buttery' smooth shift.

Also, the Mark 111 has a more complex primary.
The only real advantage to a Mark 111, is the E start.
And that needs to be fettled.

Click to expand...

And possibly the strengthened MK111 crank
Or the stronger MK111 cases
And improved head steady
Or the vernier isos, sealed swing arm pivot , beefed up frame and so on.
The rear disc is quite nice as well, I consider it an improvement on the earlier drum brake.
Changing to a primary cover held in place by 12 machine screws around the perimeter rather than attempting to hold the oil in with one central fastening was also a good step.
The 180 watt alternator was another.
The built in MK111 anti drain valve added to the oil pump seems to work well to prevent wet sumping, at least for a couple of months or more of storage.
The design of the rear wheel with it's sturdy cush hub and quick detachability is quite clever.
Unlike earlier models, you can slide a 530 sealed chain onto the MK3, if you do a lot of miles.
This might not have been a planned advantage, however Jim Comstock pointed this out to me, and sure enough, they drop right on.




Quite a few important improvements really, a lot more than just the Estart.
They do shift OK, I have both RH and LH amc trans bikes, never miss a shift with either. I can't say that one is better than the other.

Glen

Yeh, right after I posted it i was thinking of the stronger lower end and other differences.
I'd see were it went. it went......
Didn't know about the 530 chain, that's pretty cool.
This can go on for awhile, from the dash mounted ignition, different controls, through the hinged seat to the larger battery, on to the oil separator. to the slightly more rearward foot position, and there's more.
All of them add up to a different feeling machine, not a bad one, but different than what he had.
I personally don't care for the front mounted caliper, I'd turn it around.
It still won't shift like the RH.

All that said, I'd buy another.....

By the way 850dunstall, I really like that picture back in the day, very 8) 8)

according to the press release at the time , theyd improved the gear profile & material .

though this wasnt the first time theyd said that .

Think your first priority would be LOW MILES . Personally Id get one of the ( seemingly ) rusty wrecks ,
with FIVE THOUSAND on the Speedo . ( GENUINE ) at start from there , as Id assume Id be back to there
before long with most things , anyway .

If your into 750s the Pre villiers & the 73 Mk V are perhaps prefered , as a base . ( as in Fastback or
post combat ) with all the bad mouthing , Combats seem to be devalued , and theyre pretending theyre not Combats . Was a original derilect Combat on the bay recently , advertised as definately not combat ,
and was low intrest / price . ( Itd had the frame mildly buthered )

loking at your previous devise , seems your not a part No 357892 A , except for November , where its . . . TYPE .

So A Mk III with The Primary tossed , and a tooth belt , if the rubber bands dont brake -
and bung a cork in and Right Shift covers on and give it a Good Whack , would get you
somewhere sooner . If your trying uphold the prestege of the marque ,
by not letting those cheap jap. upstarts take advantage of you .



youd get a extra brake & a bit of bracing thrown in , and a nice interstate tank .
Always thought a Dingined steel interstate tak'd be good to knock some knee grips in with clip on
recesses to match . . With a 1 7/8 dia. S typeish ExHaust .
Id tend to make the accesories , as I dont think the computer assisted laser cut bolt ons match the image , of primevall force . :mrgreen:

When you add up all the changes incorporated in the MK111, and there were many more than those Michael and I have listed, it is a lot. The preceding bike, the 850 MK11a, was already a good bike with many changes/improvements over the older Commandos, which were none too shabby once the initial frame problem was solved .
I've heard it said that the British Motorcycle Industry became "complacent" and stopped trying to improve, however it is clear that Norton was all about improving and updating the Commando as production went along.


Micheal wrote " I personally don't care for the forward mounted caliper, I'd turn it around"

Maybe the best thing to do with the front disc is to remove it entirely, store it in a drawer for the next owner should he want everything stock, then slap on one of these Madass brakes or the CNW Brembo.



Re the shifting. With the LH shift there is naturally a little bit of working slack in the extra linkage. Jumping from the RH shift bike to the LH MK111 it takes only a minute or two to adjust to the difference in operation. When I first got the MK111 I used to occasionally powershift it at the red line thru the gears. It sounded just like an automatic transmission type vehicle going down the road. I stopped doing that after looking inside the gearbox and realizing how skimpy the internals are. But the shifting mechanism on the MK3 (this one at least) works smoothly enough to do this, can't ask for much more.

Glen

I recall reading the reason Norton switched the front brake to the left side was to prevent a tendency of the bearing lock ring on the hub from coming loose from braking pressures.