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by Mal Marsden - 06/16/22 7:00 pm
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Hi all,
Yes, this is a strange question, apologies.

A friend sent me a shot of his recent acquisition and I noticed the rear sprocket had the smooth side out. I was about to suggest to him that the sprocket was installed backwards, based on my own T140 rear sprocket... I went to the tech manual and sure enough, mine seems to be on the wrong way according to the illustration.

Is there a correct and incorrect way to bolt the sprocket on...?

Seen below is the (now) clean sprocket off my '78 and the way it had been mounted. Was it on the wrong way...?

[Linked Image from imagizer.imageshack.com]


[Linked Image from imagizer.imageshack.com]

[Linked Image from imagizer.imageshack.com]

My friend's Bonneville that started this whole conversation...

[Linked Image from imagizer.imageshack.com]

Thanks,
Rob


"They told me I was gonna have to work for a livin' but all I wanna do is Ride" - Jackson Browne

Current:
'75 T-160 Trident, '78 T-140 V Bonneville, '72, T120R Bonneville, '71 T100R Daytona, '13 Electra Glide, a garage Full of Guzzis, '88 Honda Hawk GT, '84 RZ350 KR, '78 Yamaha XS650, 1969 Dalesman Trials etc. and a '73 MGB for good measure... smile
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Hi Robert, Your bike is correct. Workshop manual doesn't seem to address this. However many period photos show your bike is how factory did it.

Scroll down to bike with blue tank. Expand photo. You clearly see yours is correct.

http://classicbike.biz/Triumph/Brochures/1970/78BonnevilleUSA.pdf

Here's '77, scroll to red tank.

http://classicbike.biz/Triumph/Brochures/1970/77ModelsCanadaTri.pdf

But.... It depends upon sprocket maker.... 37-7016 subs to 37-7064. Seems 37-7064 sold now, is hollowed on outside, no raised center. All flat side to hub. Friend of mine got new sprocket 47t. Was flat both sides, no hollow at all. So it looked like your friends on both sides. In any case there should be small chamfer on side you put against hub so sprocket sets flat. If sprocket doesn't fit flat & tight to hub file chamfer in sprocket center as needed.
Don


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Originally Posted by Robert Dentico
I went to the tech manual and sure enough, mine seems to be on the wrong way according to the illustration.

There's an explanation for that, as the T140 disc rear wheel parts diagram is a revision of the T160 diagram. The T160 had a dished sprocket so a T140 owner looking at the diagram could get the impression the recess goes on the inside. The raised inner is the same height as the sprocket teeth so it wouldn't seem to matter which way the 37-7016 sprocket is fitted for chain alignment.

The later 37-7064 sprocket (from '79) can be supplied as a replacement for 37-7016, however, that sprocket does not have the raised centre so needs to be fitted with the completely flat side against the hub.

https://www.classicbritishspares.co...ar-sprocket-47t-37-7064-1976-82-tr7-t140


[Linked Image from i.postimg.cc]
(Note the T160 LH chain adjuster, item 16, with the boss that the T140 item doesn't have that wasn't redrawn.)

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My early 1978 T140V has the dish side out. Low mileage, two owners.

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The pic of the T140 37-7016 sprocket shows that it is a recess (rather than a 'dish' that the T160 sprocket in the background has that is resting flat on the same surface).

[Linked Image from i.postimg.cc]



Edit: The oversized holes in the friend's sprocket suggests it could be flat on both sides.

Are they a type of USD shock in the pic like the original Gas Girlings or at least Shocks that can be fitted either way up bacause not all standard Shocks work when inverted as the factory manual warns against for standard 'oil' Girlings.

[Linked Image from i.postimg.cc]

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Thanks guys,
Don, the brochure photos are a good reference, glad to see that the one on my '78 was at least on correctly. I can only locate flat on both sides for replacement.

L.A.B.
Indeed that is the impression I came away with, until you point out the illusion and T160 adjuster, I had not noticed and now I can Only see that.

As always, I appreciate you all.

Best,
Rob


"They told me I was gonna have to work for a livin' but all I wanna do is Ride" - Jackson Browne

Current:
'75 T-160 Trident, '78 T-140 V Bonneville, '72, T120R Bonneville, '71 T100R Daytona, '13 Electra Glide, a garage Full of Guzzis, '88 Honda Hawk GT, '84 RZ350 KR, '78 Yamaha XS650, 1969 Dalesman Trials etc. and a '73 MGB for good measure... smile
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Never rely on photos or drawings or how the sprocket was previously installed.…If you want the best alignment do run a straight edge between the gearbox and rear drive sprockets…


61 hot rod A10, 89 Honda 650NT .On a bike you can out run the demons
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But a V8 engine is a good start for me
Think I'll drive to find a place, to be surly"

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