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
 
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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
 

ILLF8ED

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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.
 
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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
 

ILLF8ED

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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.
 
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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
 

MichaelB

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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?
 
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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
 
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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
 
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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
 

Ron L

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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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