Tach drive question

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My '72 parts book shows the part numbers as 06-1089 for the gear and 06-1090 for the housing. The part numbers seem to have changed at some point, to 06-5201 for the gear and 06-5200 for the housing.

Does anyone know what the difference is? Can the new parts be interchanged with the old?

thanks,
Debby
 
Debby

The new numbers are probably for the MK 3 type which has a small "O" ring for a seal. They probably interchange with older bikes but I assume need to be used as a set since the numbers for both parts changed. One of the parts purveyors could tell you for sure.

Half the fun of owning a Norton is figuring out these little discrepancies.

Scooter
 
Tach drive

Hi Debby,

Are you missing the tach drive completely? I would think all the drives would fit from '70 750 to "75 850 MkIII.

Phil Radford - Fair Spares America can machine the housing and add a "proper" oil seal replacing the o-ring that eventually goes bad then leaks.
 
I think Phil answered my question! It's the groove for the second o-ring. Old part number, as shown in my parts book, doesn't have it. New part number, as stocked by all the suppliers now, does have it.

So with the oil seal I don't need either o-ring?

David: I do have a functional tach drive but it leaks in a big way. It's currently wearing a little red rag to absorb the oil. I want the oil seal mod but don't want to be without the tach for a long period of time. Guess I should call Phil Radford and see how long it takes.

Debby
 
tach drive

I hate to say it, but there's a tach drive on "evil-bay" with a buy it now price that's cheap. Throw that one on then get Phil to machine yours. Afterward just sell it again if you don't want to keep it.
 
I made a jig to machine a cavity for a seal in the housing. I don't use it because I found a more effective way to stop the leak. It's so simple, three O-rings a certain size stacked up into a tapered tower. This set up out does the seal by far. Mike @ Walridge Motors turnned me on to this. norbsa
 
I was just looking at a tach drive and was wondering why an o ring or rubber bushing similar to the oil pump bush wasn't engineered in the taper.
Regarding your o rings, are they all the same size, or do they decrease?
 
norbsa48503 said:
I made a jig to machine a cavity for a seal in the housing. I don't use it because I found a more effective way to stop the leak. It's so simple, three O-rings a certain size stacked up into a tapered tower. This set up out does the seal by far. Mike @ Walridge Motors turnned me on to this. norbsa

Would you care to elaborate on that?

debby
 
Well when I got them from Mike I didn't think they would work so I installed them without measure. Yes Michael B they got smaller at the top. Guess you guys will have to email Mike at Walridge Cycle to get your sets. Hey don't do what I did, get two sets one for install one for measure. norbsa http://www.walridge.com/default.htm
 
Ok, I'll try to contact walridge and see if they can help me with that.

Another question: I need to replace the mounting screws too. DPO installed some phillips-head screws then thoroughly butchered the heads. Does anyone know what size those screws are? Are they something I can buy at the local hw store (UNF) or do I need to buy them from walridge etc?

Debby
 
Debby,
Those are 1/4-20 X half-inch long SAE. A couple nice polished stainless allens or button-heads would look good there! :wink:
 
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