Britbike forum Forums British Motorcycle specific Brands Norton bulletin board Norton MKIII Air Filter

I've spent several hours searching the Norton manual, the "Access Norton" archives back as far as they go, and this forum's archives back to 2006 (177 posts containing the words "air filter") and can't find any information on this question. Maybe it's just too simple.

MKIII with the stock airbox. Took the front plate off, and the filter was installed on the "floor" of the airbox.



So (probably as long as I've had the bike), outside air has been coming straight through the intake horns under the airbox and into the carbs, bypassing the filter element (hence the ring job I'm doing now).

There appear to be three positions, three slots, that the filter can be slid into. One is where it was when I opened it, on the floor of the airbox, useless. There are two more slots above it; when I remove the filter and slide it into the top slot, it appears to be in the right place - air that comes in through the intake horns has to go through the filter to get to the carb mouths.

Am I the only one who ever noticed that there are apparently three ways the filter can go in? I swear there's nothing in the manual or on any of the forums about it ..... ?

The present filter is not in that great a shape, so I'll see if CBS can get me one in their usual two days. The carbs and head are off now so it's easy to get the filter in and out; is it still possible to change that filter element with the two Amals in place, which they will be tomorrow afternoon I hope?

Thanks!

Lannis

It is the same as my Mk2a.
The filter with its internal frame goes in the middle slot/recess.
There should be another foam rectangle that seals the access door at that front location. 06.4174

Somewhere in that location the filter will slide in, a light smear of grease optional on the perimeter .

Thanks much! I don't know if the filter element will come with the foam seal for the front access, but if it doesn't, it doesn't seem like it would be hard to make one ....

Lannis

It is a separate item at around $9. To rich for my Moto Guzzi ness.

I'm sorry to keep asking what should be simple questions, addressed in 100 different places on the Internet or on this forum, but I can't find it anywhere. Not one word about the flat foam MkIII air filter in the Norton 69 - 75 manual, just the big automotive type.

The pics I showed above, where the air filter simply slides in and out of the airbox, was taken with no cylinder head or carbs on the bike.

The cylinder head and carbs are on the bike now. I'd like to slide the air filter back into the airbox, but there doesn't appear to be any way to do it with the carbs and cylinder head in the way. I've been treating it like a Chinese puzzle, turning it every whichaway. But it's a rigid item, doesn't bend, and it just looks like it absolutely will not go in.

This can't be as hard as it seems. Although I'm not a patient guy, I have a very patient helper, and she will calm me down and say "let's look at this logically" when I'm ready to take a hacksaw or a stick of dynamite to something that's not working, and we STILL can't get it. How come I've never heard about this issue before .... ? I've read everything I can get my hands on and it's still not helping .....

Lannis

The Mk3 manual is for Mk3 only.
Air filter, Section E10.
https://nortonmotorcycles.org/media/manuals/850_man.pdf

Thanks for that. I didn't have that manual, didn't know there was a separate one since the one I was using referred to the MkIII '75 models when telling me about torque values, and differences in the heads, and everything else.

Lannis

But it's a rigid item, doesn't bend, and it just looks like it absolutely will not go in.

Goes in from the right side.
The narrow front tab goes toward the center but hangs low.
Pull the head oiler line toward the extreme right edge of the opening and the rounded edge of the filter rotates about the oil line while the tab enters the filter houseingt opening.the front filter edge is running at the very bottom edge of the barrel/crank case junction even entering the little curved filter section at the middle ....as the filter rotates and enters the housingyou you can raise the front of the filter element and guide it inwarrd ( keeping the oil line out of the way ) and putting the element in the groove pointed out by Les P.

I just did mine a second ago.
Tough to describe but once you see exact process it is relatively easy.

Dave -

No, you described it perfectly. I read what you posted, walked out to the shop, and in one motion, about 2 seconds, I had the filter in after fighting it for what seemed like hours.

All I can say is that I'm learning a lot about this bike, and I won't have to ask these questions again.

Thanks, Les P., Dave, L.A.B .... couldn't do it without you and the others that have helped in this process.

Lannis

oh lannis do you peruse the accessnorton site? i got my Commando education (still learning) there

If you ignore all the 'opinions' there that don't have a clue !

Yes, I'm on over there. I've posted about things like the anti-wet-sumping modifications to the timing cover and so forth.

But since I'm here on this site anyway, AND some of the smart guys from other there are here too, I just use (hopefully not abuse) the expertise here.

Lannis