Fitting a Bob Newby belt drive

robs ss said:
I guess you're talking about the cable lever inside the cover of the gearbox?
I seem to recall someone (@dynodave ?) talking about the different "cam" profiles on this lever across the different models of Dominator and Commando.
This profile gives different effective leverage at different amounts the handlebar lever pull.
Cheers
Click to expand...
I'm talking about the distance from the lever's pivot on the perch to the barrel, or nipple, on the end of the cable. Triumph used 7/8" I believe. The 'box is a Pre Unit Triumph four speed, but I think the same distance lever was spec'd for a great deal of Triumphs over the many years.

Don't know what Bob spec'd for lift, but my lever's 1-1/6" pivot-to-nipple distance gives about .060" (with very little slack in the cable), which seems to barely get the job done of no drag. But... the lever's pull is pretty stiff.
 
Onder said:
Instructions? I got no instructions! But if you ping him he does respond and you can get spares from him as well.
Have two of his belt clutches and I found it impossible to adjust the belt free play to what most say is correct. In other words
the belt will rub on the alternator tower castings. Yes, I "relieved" them but until I took a lot of the free play out it would eat the belt. Having a TTI box there is likely less worry about too much load on the shaft and bearings or that is what I tell myself.
As for the belt mine is low miles yet, 8K, but I think Kenny at NYC NW uses a stronger one and I think he posted this on this list
some time back. If not at some point Ill see if I can dig out my extra belt and get the numbers off it.
One other thing: the back of the basket tends to get eaten by the gearbox shaft and Kenny made me a hardened washer to
fit in between. This was for the Norton and the TTI.
Click to expand...
Hi Onder: new to the site, just joined after seeing your thread. I am looking at the TTI AMC 5 speed box for my 58 pre unit Thunderbird tracker build.
I have reached out to Bob regarding his clutch but any feedback and tips you could give me on fitting issues would be greatly appreciated.
I have a Tony Hayward belt clutch that I now can’t use because of the Norton spline on the TTI box. I haven’t ordered anything yet but any advice would be gold.
Oh the joys of building!!
 
Last edited:
Jrodd said:
Hi Onder: new to the site, just joined after seeing your thread. I am looking at the TTI AMC 5 speed box for my 58 pre unit Thunderbird tracker build.
I have reached out to Bob regarding his clutch but any feedback and tips you could give me on fitting issues would be greatly appreciated.
I have a Tony Hayward belt clutch that I now can’t use because of the Norton spline on the TTI box. I haven’t ordered anything yet but any advice would be gold.
Oh the joys of building!!
Click to expand...
My TTI is on the 74 Commando so no idea about fitment on early bikes.
However it is a bullet proof and shifts very easily. Very happy with it and worth the cost for me.
BNR clutch and belt have been, overall, good. Pointers: you might ask Bob about clearance on the front pulley I never have and should. A slightly smaller pulley would be a good idea. Failing that, I also have never gotten around to modifying the inner primary cover to achieve
more clearance beyond removing material on the bosses.
Next thing is the plate that runs under the pressure plate. I had a lot of wear on the cover surface even with a softer plate Bob recommended. Instead I use another steel plate. Seems that you get a lot of dust build up so I remove the plates every 2k or so and clean. Easy on my bike with rear sets, primary cover comes off with one nut, remove plate you are there. Push in a small amount of grease for the little ball bearings too. Lever pressure is low, way more travel on the lever than you need so for me a big success. Have BNR on three of my bikes.
Only wish I could put one on my Trident, which has been done but it is expensive. Oh well....
Contact me directly if you want more info.
 
Last edited:
Let me add a comment on lever pressure. No slip problems on my pretty much stock engine but I do run it up to near 6k now and then
no sign of slippage. I weigh less than most people though.
Now as for the 1 1/16 " lever, that was stock on later Tridents. It is barely adequate on my T150v unfortunately the only one I know
that has more travel is my old Enfield Interceptor that doesn't need it.
On the Commando it has the stock lever but the later Commando may
have a perch that gives slightly more travel than earlier ones, ie, the
71-73 alloy type. On mine it is a black alloy perch at 1 1/16" centres.
 
Onder said:
My TTI is on the 74 Commando so no idea about fitment on early bikes.
However it is a bullet proof and shifts very easily. Very happy with it and worth the cost for me.
BNR clutch and belt have been, overall, good. Pointers: you might ask Bob about clearance on the front pulley I never have and should. A slightly smaller pulley would be a good idea. Failing that, I also have never gotten around to modifying the inner primary cover to achieve
more clearance beyond removing material on the bosses.
Next thing is the plate that runs under the pressure plate. I had a lot of wear on the cover surface even with a softer plate Bob recommended. Instead I use another steel plate. Seems that you get a lot of dust build up so I remove the plates every 2k or so and clean. Easy on my bike with rear sets, primary cover comes off with on nut, remove plate you are there. Push in a small amount of grease for the little ball bearings too. Lever pressure is low, way more travel on the lever than you need so for me a big success. Have BNR on three of my bikes.
Only wish I could put one on my Trident, which has been done but it is expensive. Oh well....
Contact me directly if you want more info.
Click to expand...
Thanks for the info Onder, I’ve pm,d you more details.
 
Jrodd said:
I have a Tony Hayward belt clutch that I now can’t use because of the Norton spline on the TTI box.
Click to expand...
Isn't a Norton clutch center available for a Hayward belt?

Onder said:
You might ask Bob about clearance on the front pulley I never have and should. A slightly smaller pulley would be a good idea. Failing that, I also have never gotten around to modifying the inner primary cover to achieve
more clearance beyond removing material on the bosses.
Click to expand...
Not sure about the Commando, but on the alternator pre unit Triumph kit, the Newby front pulley just nests the outer guide over the rotor, and it already puts the rotor outboard enough to necessitate pushing the primary cover out 3/16" to clear, so a smaller pulley would push the rotor out another 3/8-ish" out. Relieving some material off the stator mount will be needed. Ignore, of course, the above if you're not running an alternator.

If you do end up with a Newby, you might get the belt kit first so you can let TTI what length mainshaft you'd need, as they have several.

Top shelf build! Build threads with lots of pics are not frowned upon. Even if they're Triumph builds! 😆
 

Similar threads

B
BOB NEWBY CLUTCH (BELT DRIVE)
Replies
4
Views
162
t ingermanson
t ingermanson
mean gene
  • Locked
Bob Newby
Replies
1
Views
912
Son of Siredward
Son of Siredward
Matchless
  • Locked
Norton vs Bob Newby clutch (2016)
2
Replies
33
Views
7,022
worntorn
W
Back
Top