Plastic Airbox

Worse still, the motorcycle must be assembled STARTING with the plastic airbox.

You think I'm kidding? Wait till you try to install it.

grandpaul said:

Worse still, the motorcycle must be assembled STARTING with the plastic airbox.

You think I'm kidding? Wait till you try to install it.

Click to expand...

I'd like to contend with that statement. I'd REALLY like to contend with that statement!
I just had the 'pleasure' :roll:
Despite the warnings, I'd already fitted the barrels and head before I realised, and by Chr!st it was a pantomine getting the filter box in. It can be done, but I can't remember how...I think top in backwards from the left hand side then rotated into position, but I had so many attempts... :evil:
Next time...no, there won't be a next time.

Edit...Thinking about it, the MkI/IIA box doesn't have the brackets riveted on like the MkIII version - if it had I would have had no chance!

A google search came to this thread.
I just put the air box (Mk2a) back in and it took perhaps 15 seconds to get in place. ?
What is this dzus fastener,mine has a Mk3 type battery tray with a bolt from the bottom of it passing through the side cover with a nut ?
I guess that is not stock ?

The airbox is pretty awful alright mine is under the house
Must be a knack getting to get it in in 15 seconds. If I tried that there would be paint off everywhere and a distorted airbox
I removed the bracket that holds the side cover and mounted it on a home made one and fitted a K&N RC8090 pod filter which accomdated the breather and oil feed
Sidecover fittings vary between interstate and roadster
I used the Deuz clip but will be working on improving that piece of genius design that belongs in the "What the?" basket

http://i1267.photobucket.com/albums/jj5 ... G_0798.jpg

Jed

Time Warp said:

What is this dzus fastener,mine has a Mk3 type battery tray with a bolt from the bottom of it passing through the side cover with a nut ?
I guess that is not stock ?

Click to expand...

No, it isn't stock if there's a bolt securing the side panel instead of a plastic Dzus fastener [15 & 16] (and Dzus receptacle [24]).





The 850 MkIII battery tray and Dzus side cover fastening arrangement is also different again to the 850 1A/2A battery tray.

From what I can tell, the main difference between a Mark IA/IIA battery tray and the Mark III battery tray is that the Mark IA/IIA has a bracket for attaching the left-hand side panel. If you have a Mark IIA battery tray you can easily convert it to a Mark III by simply cutting off the side panel mounting bracket. I noticed another minor difference between the two battery trays. The Mark IA/IIA stiffening bead that runs lengthwise rubs on the gearbox cradle's top tube while in the Mark III battery tray Norton flattened that part of the stiffening so that it won't rub on the gearbox top tube. So if you have a Mark IIA battery tray in hand, I would recommend hammering the stiffening bead down where it rubs.

I found that the Mark IIA's side panel is rather easy to remove and replace, maybe a little too easy. Maybe that is why Norton moved the DZUS fastener up under the seat area. I would recommend having replacement Dzus parts on hand. They do break from time to time.


This is a picture of the Mark IIA zeus anchor attached to the battery tray. It snaps into the rectangular hole that is in the battery tray.



This is the Dzus fastener assembly that is used on the Mark IIA.The Dzus anchor part number is found in the Mark II/IIA supplementary parts list page (group) 31 while the fastener stud and retainer are found in page (group) 25.



This arrow shows where the gearbox cradle rubs on the stiffening bead. It is very hard to see in the photograph that I had already flattened the stiffening bead at the rub point to gain clearance.

Thanks for the excellent replies.
I had just got a email from Phil at Andover Norton and have replied with those part numbers to add to the current order (2 sets).
I guess my 850 is a Mk2a but has a early build date of 12/73,I thought wrongly the Mk2a was the last right hand shift model before the MkIII and after the Mk2.
It has the plastic air box with the ignition switch bracket with side cover pin bolted to it,a battery tray similar to that posted.
The chain guard does not have the cut out for brake adjustment ?
The fuel tank I can not quite figure out,I thought they had the rubber discs like my fastback but it seems to have four mounts similar to exhaust / head steady items screwed into the tank,the right hand front frame mount has been hacked a little to get the stud to fit and and plate at the rear Interstate style.
The kill switch button is red like later Triumphs,both have the long wing flipper.

311032
Although a nice (looking) bike it needs a lot of work to get it to a usable stage.

Time Warp said:

I guess my 850 is a Mk2a but has a early build date of 12/73,I thought wrongly the Mk2a was the last right hand shift model before the MkIII and after the Mk2.

Click to expand...

Mk2 and 2MkA models (307311+) were both produced during the same period from mid-late '73 (until MkIII).

Time Warp said:

The chain guard does not have the cut out for brake adjustment ?

Click to expand...

The cutaway chain guard (and rear brake plate with the two brake lining inspection plugs) wasn't fitted until January '74 according to the 2/2A parts supplement.

Time Warp said:

The fuel tank I can not quite figure out,I thought they had the rubber discs like my fastback but it seems to have four mounts similar to exhaust / head steady items screwed into the tank,the right hand front frame mount has been hacked a little to get the stud to fit and and plate at the rear Interstate style.

Click to expand...

Possibly a PO mod.?

Time Warp said:

The kill switch button is red like later Triumphs,both have the long wing flipper.

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'73 and '74 "850" brochures show a red kill button.
http://www.classicbike.biz/Norton/Broch ... chures.htm

Switches with extended flippers were also fitted 1973-on:
1973 "750" brochure.
http://www.etmoteur.fr/images/norton_co ... erieur.jpg

Time Warp said:

I guess my 850 is a Mk2a but has a early build date of 12/73,I thought wrongly the Mk2a was the last right hand shift model before the MkIII and after the Mk2.

Click to expand...

You are not the only one that thought wrongly about the Mark II and IIA's. It seems as though most book writers and magazine journalists alike don't know what an 850 Mark II is, or even that it exists. I have seen a number of magazine articles on the 850 'Mark IIA' when in fact the featured bike is a Mark II. Then they go on to state the differences between the earlier 850's and the later Mark IIA's. The differences that they point out have nothing to do with the 'A' portion of the motorcycle. These book and magazine writers actually made model identification more complicated than it needed to be.

Basically the 850 Mark IA and IIA are the special noise reduction model of the standard Mark I and II 850's. Think of the 'A' in Mark IA and Mark IIA means 'Absence of noise' and basically what that entails:

1. Quieter annular discharge mufflers
2. A large silenced plastic airbox
3. Higher overall gearbox gearing

Of course to make all of these 3 items work, there are a number of detailed changes to the motorcycle. For the overall gear ratios, it was a simple change. They changed the countershaft sprocket from a 19 or 21 tooth to a 22 tooth sprocket which of course meant using a longer drive chain. For the muffler, they used different header pipe part numbers, different muffler mount brackets and a different kickstart lever. The plastic airbox had quite a lot of changes that needed to be done. If you have an Interstate model, you need a different right hand side cover to gain clearance around the airbox. For all IIA models, they needed a different battery tray so that the battery fits sideways. To do this they needed a different left hand side cover, which of course meant they omitted the tool tray in the left hand side panel and placed a plastic tray under the seat. This required relocating the turn signal flasher and the rectifier (a special bracket was required to mount). There is an oil separator and related parts and pieces added for some reason. The inlet and outlet oil pipes that are mounted to the engine needed to be reconfigured to clear the airbox assembly. And also they used different part number carburetors (this change was not only because of the airbox but also because of the mufflers). There are some other minor detail differences - hose length, etc.

The other changes for the 1974 year model Norton are the same for both the Mark II and IIA's. For instance the seat, the instrument cup covers, swing arm spindle change, the chain guard, alternator rotor, etc.

The picture of your Norton looks to be a Mark IIA with standard Roadster peashooter mufflers installed. It sure looks nice in red. I can see why Norton sold so many red ones! I have a black 1974 Interstate Mark IIA that I am collecting the parts and pieces to make into a Roadster. After looking at your picture, I just might go with red. My Norton started life out as a Mark IIA but in fact it has just a few pieces remaining that make it a Mark IIA. All that is left is the side panels , kickstarter and header pipes.

G'day!
Pete

PeterJoe said:

Basically the 850 Mark IA and IIA are the special noise reduction model of the standard Mark I and II 850's. Think of the 'A' in Mark IA and Mark IIA means 'Absence of noise' and basically what that entails:

1. Quieter annular discharge mufflers
2. A large silenced plastic airbox
3. Higher overall gearbox gearing

For the overall gear ratios, it was a simple change. They changed the countershaft sprocket from a 19 or 21 tooth to a 22 tooth sprocket which of course meant using a longer drive chain.

Click to expand...

Not just higher overall gearing, as the Mk1A also had a higher ratio second gear.

The higher 2nd gear was subequently used for both Mk2A and Mk2 models and only the higher ratio 2nd gear pair (064639 & 064630) appear in the Mk2/Mk2A parts book.