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Late T140 primary adjuster
#776113 06/11/19 12:22 pm
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How does the adjuster work on the post-1979 models? The earlier ones had a hard to reach sleeve nut which you had to screw in on the threaded rod, drawing it towards the nut and bowing the tensioner blade upward. But the late sort has (going by the parts book) a steel screwed-in boss into which a long hex-headed screw fit, with a locknut. It looks as if the screw must somehow push the tensioner blade, but the threaded rod is still shown in the parts book illustration - which would get in the way of the push-bolt, surely?

I've had a belt primary so haven;t had any of this, hence not knowing or being able to look at it. But I now think the new-ish belt could do with a tad of tension - that's why I need to understand the system, if anyone can kindly explain it?


If anything other than a blank space is visible here, something's wrong.
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Re: Late T140 primary adjuster
Tigernuts #776117 06/11/19 1:45 pm
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Originally Posted by Tigernuts
But the late sort has (going by the parts book) a steel screwed-in boss into which a long hex-headed screw fit, with a locknut. It looks as if the screw must somehow push the tensioner blade, but the threaded rod is still shown in the parts book illustration - which would get in the way of the push-bolt, surely?


Firstly, the later 71-7255 tensioner rod isn't threaded.......

[Linked Image]

....and the parts diagrams show it facing in the wrong direction, so the larger diameter section of the rod goes between the tensioner blade (and trunnion) and the adjuster bolt, in the space the earlier adjuster sleeve would have occupied.


Re: Late T140 primary adjuster
L.A.B. #776123 06/11/19 3:16 pm
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That's very helpful LAB - it explains why, when feeling inside the hole in which the steel boss is fitted, all I can feel is a blank surface - it is clearly as it should be, and when the long screw is screwed in, it pushes the larger diameter part in your photo and causes the blade to arc. This forum is great for almost instant advice - thanks.


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Re: Late T140 primary adjuster
Tigernuts #776188 06/12/19 2:22 am
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If you do use a tensioner with your belt drive, make sure that the slipper is polished right up. Remove any friction material that the chain runs on and polish away.

I did this on my previous belt for the Trident [it was a looser fit and needed tension], my newest belt didn't need it.

Re: Late T140 primary adjuster
Tigernuts #776212 06/12/19 7:25 am
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Originally Posted by Tigernuts
That's very helpful LAB - it explains why, when feeling inside the hole in which the steel boss is fitted, all I can feel is a blank surface - it is clearly as it should be, and when the long screw is screwed in, it pushes the larger diameter part in your photo and causes the blade to arc. This forum is great for almost instant advice - thanks.

Very useful info, in case a later bike comes my way. However, long time ago I owned and overhauled a Harris made Bonnie, a 1986 model. I can't recall this set-up on that bike.
Did Harris revert to the earlier system, or is it brain-fade on my part? That wouldn't surprise me to be honest.

Re: Late T140 primary adjuster
Stein Roger #776214 06/12/19 8:12 am
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Originally Posted by Stein Roger
Very useful info, in case a later bike comes my way. However, long time ago I owned and overhauled a Harris made Bonnie, a 1986 model. I can't recall this set-up on that bike.
Did Harris revert to the earlier system, or is it brain-fade on my part? That wouldn't surprise me to be honest.


According to the Harris parts book, yes, it seems they did revert to the earlier system!



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