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Discussion Starter #1
OK, I am confused.

I have an early 5 speed 1972 Bonneville. I was told that the 5 speed Bonnies do not have an oil seal in the circular cover plate behind the clutch basket. Well, when I pulled the basket and center hub off the shaft there was an oil seal there.

I would like to replace this seal with a new one as I believe this was the source of my primary leak. The chain is always very oily and there's a constant film of oil (that collects dirt) on my rear wheel. This is neither clean nor safe.

However, the parts manual says this seal is four four speed boxes only. If I buy this seal will it fit my plate bore and shaft??? Maybe I have one of those very early production 5 speeds and they used this seal then???

Does any one have an idea?

Thanks!
 

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bikeman 71,
The Sprocket Cover Seal for Triumph Twins/5 Speed, 1971 on, is #60-3500. But, you need to go one step further by replacing the Gearbox Sprocket Seal which is #60-3512. You remove the front sprocket and replace this seal pressed in the gearbox. For insurance you can coat the the edge of the seal with some hi-temp silicon, don't over do it with the silicon. Make sure to put the seals on with the inner seal spring pointed in the right direction by notating how they were on before removing.
By doing both seals now, you will insure you've got the leak covered as it's hard to discern which seal is actually leaking. So replace them both.

roadduster2
 

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"I was told that the 5 speed Bonnies do not have an oil seal in the circular cover plate"

You were misinformed.
In addition to roadduster, its an idea to seal the blind layshaft needle roller bearing.


Also the 5-speed has an O-ring which fits over the splines on the 5th gear, behind the tab washer.



This can also be sealed:

 

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Discussion Starter #4
Thanks Roadduster and Caulky.


How hard is it to replace the gearbox layshaft seal with the shaft installed? Do I need a special tool to install the seal or might I make do with a large socket as a press-in tool? Not sure how much of an interference fit at the OD to expect.

I haven't removed the primary sprocket cover seal yet but it looks "ok" as installed. I don't see any tears or inverted lips. Interestingly (and a bit a gross I might add), I did find a long piece of human hair wrapped around the shaft going past the seal lip. This wonderful little piece of DNA must have belonged to the PO. Anyway, I suspect it may have been enough to prevent the seal lip from laying down properly on the shaft and possibly causing a leak path. I plan to replace the seal anyway since I've gone this far.

Also, how can I best remove the woodruff key without damaging it? Seems to be tightly fitted into the key slot. I wasn't able to dislodge it using a punch and lightly tapping with a mallet.

Thanks again!
 

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The `blind` layshaft seal was only a suggestion, as it sometimes weeps oil.
I think I mixed up some araldite to seal mine.
Make sure its clean, if you want to seal it.
There is no special part/number for it.
The reason why I replaced my needle roller bearing was because the P/O had fitted an open one.
This was sealed with some kind of mastik and leaked.

The woodruff keys are curved in their slots.
A small srewdriver or chisel tapped underneath the key should lift it.
 

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Discussion Starter #6
Thanks again for your feedback, Caulky. I appreciate your advice. :)

Hopefully, replacing the o-ring and cover plate seal, and sealing around the splines will make the leak go away. I'm tired of adding to Valvoline's fortunes.
 
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