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79 Bonneville Front seals

2K views 12 replies 9 participants last post by  htown16 
#1 ·
I am replacing the front seals. I have removed the allen bolt in the fork leg. From what I see in the manual and read in this forum the bottom part should now separate from the tube. Is this correct? I dont see any clip or anything else aroud the seal. It looks like just a protective plate on top of the seal.

How much if any force is necessary to separaate the bottom from the tubes? Does any one know of any fastners I have missed to separate them?

Thanks for the help.
 
#2 ·
There should be a circlip on top of the fork seal unless the seals were previously replaced with older ones that fit 650's. I think the earlier ones are too thick to allow room for the circlip so it's just left off.
Once you've removed the circlip you should be able to seperate the fork slider from stanchion. I think it's the inner bushing that actually pops the seal out as it passes by so think of the force as if you're using a slide hammer.
Did you remove that protective plate?
 
#4 ·
A couple of points

1) the earlier, thicker seals work better and are less likely to leak. They are just a push fit.

2) there is a Dowty seal in the bottom of the fork leg. The allen screw fits through it and it forms the lower seal. It should be replaced with a new one. Note:- it sits in a recess in the bottom of the leg and care must be taken to ensure that it is properly located before you put the allen screw back in. Once located, put the stanchion back into the lower leg and push down to the bottom of the leg. Only then insert the allen screw and tighten.
 
#5 ·
The earlier '79 T140's didn't have the circlips. Instead they had a thicker interferance fit washer holding the seals in place. The later '79 T140's did have the circlips holding thinner washers in place. Lots of people will tell you that the older seals are better, but I don't think that there is anything wrong with the later style seals. I've got 5 T140's in the garage, all with the later seals and none of them leak.
 
#6 ·
I don't think that there is anything wrong with the later style seals. I've got 5 T140's in the garage, all with the later seals and none of them leak.
I understand that the thinner seals used by Triumph were fine. I have been advised by a couple of the main spares suppliers inc Reg Allen that unfortunately the replacements for the thinner seals now available do not work as well. I have had to go back to thicker seals on both my T140 and my TR65.
 
#7 ·
Interesting re seal comparisons. But back to the question - surely, whether fitted with newer type seals or the older type, once the allen screws are removed from the bottom ends, the sliders should just slide off without the need for any particular force?

As for the 'bushings' - maybe I've missed something re. the post-1980 models, but as far as I know Triumph OIF forks never had any bushes?
 
#9 ·
The Plewsy video posted by Dave M shows how to do it. There are no bushes, nothing 'pushes' or 'pops' the seals out, and there's no need for any slide-hammer action! Getting the sliders off is easy but getting the old seals out is not so easy - you're never using them again so be generous with the heat.
 
#11 ·
Rather than start a new thread, I figured I would pose my query on the tail end of this one...the last time I replaced my seals, I was told that they are the same size as a yamaha (insert solution here) My query is, a yamaha what? The reason being, is so that I can buy some off the shelf, rather than mail order from a dedicated old trumpy part dealer. Doesnt need to be Yammy, any ones will do... I am not so much of a puritan that I need genuine Triumph parts for things such as this...
 
#12 ·
I seem to recall the outside diameter of the seal is an Imperial size.It's not likely for Yamaha to use Imperial seals.
They would be the same seals as BSA OIF forks
I think Norton use the same size stanchion,so they could be the same too.
1.361" is the stanchion size.
 
#13 ·
An inexpensive seal puller that levers the seal out makes taking the metal retainer out a lot easier without damaging the top of the fork leg like a screwdriver will do. Any auto parts store has them.
 
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