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45 Tooth Rear Sprocket

10K views 11 replies 4 participants last post by  banditz 
#1 ·
Hi to you all.

I have just got my T140V 1978 back on the road after a 10 mth rebuild.

I have a standard front sprocket and a 45 tooth rear sprocket, after a ride out of about 2 miles it feels like i am under geared and riding a trail bike, i am going through the box that quick,has anyone got any thoughts about sprocket set up's.

Any help would be good and thanks for reading.

Simon.
 
#2 ·
Hey Simon,

I was talking to someone else here on the pages about sprockets.
I forget who. Anyway that lead me into looking at the types of
sprockets one could get to go a little faster. I would take that
you have the 20 tooth in the front.

I had found in the past a 21 tooth for the front but the teeth are
shorter to fit into the inspection cover. Also a 22 tooth front
sprocket can be had as well. As for the rear I was able to get a
43 tooth unit I am hoping to get this on my machine this weekend.
I do have the 20 tooth on the gearbox. This would get me
from 60 to 65 mph and still at only 3500 rpm. So with a four
teeth removed I gain 5 mph at the same rpm.

Also remember that adding one tooth on the front will have a greater
effect than subtracting one from the rear.


What I really want is a costume fifth gear (or at least what we all
call fifth gear). Note fifth gear is not fifth gear as fifth is just locking
the input to the out shaft. In truth fifth gear in the transmission
is just at transfer gear that first through fourth use to complete
their total reduction. I would love to lower this transfer gear to
say a 22 14 count for the gears. This would lower the first to fourth
gears and make the split at fifth so the largest sprockets can be
used, that would be 22 front and 43 rear.

I wonder if anyone out there can make gears?

Pookybear
 
#3 ·
Hi Pookybear,

Thanks for comming back to me, i would rather not change the front sprocket as i have only just finished my rebuild and as i understand i would need to pull the clutch and all out to do the job, i have been on to a sprocket maker by phone and they will make me one with 40, 41 or 42 teeth anodised for the rear at £50 delivered to my door, what would your advise be on these teeth options.

Simon.
 
#4 ·
hey Simon,

no problem with the answer, we are all looking for them. As for
what to advise.. hummm. Do not know right now. I am planning
to install the 43 tooth unit in this weekend. So if you are not in
a big rush, as in can wait untill next week, I can give you some
feedback on the 43 tooth setup. Or if someone else has this
setup already please chime with your thoughts.

However, in the end if you decide that you wish to go beyond
a 43 tooth setup I would have to say the next would be the 41
tooth.

I picked the 43 and would say the 41 next because these are
both prime numbers. As you have stated you just finished your
rebuild and yes the front sprocket is a pain. Besides, any of the
go fast sprockets are not prime numbers 20,21,22.

As for the why of prime, it gives a little better wear on both the
chain and the sprockets.

I shall let you know what I think of the 43 and 20 setup early
next week if no one else chimes in on this matter.

Pookybear
 
#6 ·
Ok Simon,

I got busy today, because I could not wait so when I got home
spanners started to fly. Anyway the 20 43 setup is great. It
worked out from the 20 47 setup that it is like I moved up a
gear. I would not have thought that from just a 8.5% overdrive
effect. Still easy to get off the line as well so I am pretty
happy. Bike does not come off the line like a shark anymore,
but after the first 10mph starts to run like a freight train.
Also notice it seemed to smooth out the bike as well, feels much
more fluid. And then there is the lack of the vibration from the
extra rpm, less noise, and wear and tear on the engine and me.

In the end the driving in my normal way, I had to be down one
more gear in traffic. As in if I used to use fourth I am now in
third to keep the same rpm. The gain is really anything about 45
mph for benfits listed above at the end of the last paragraph.

So for the facts, I am now using a 105 link chain. Here is the
problem for going to a higher geared sprocket. The chain guard
has a small tube welded to the swing arm. If I do not keep on
the adjustments on the chain on the 43 sprocket; it will get hit
by the chain. Now a 41 sprocket could be used but you will have
to do something about that chain guard mounting point first to
make room. Still it can be done with a custom 41 unit but it will
take that little change.

So I hate to say it but I would go for the 43 sprocket first and
then if you need less gear still, do a 21 on the front. I may
ponder that one latter. I guess I am going have to find on of
those 21 units to see just how much shorter the teeth are as
compaired to the 20 tooth units. The last thing I want is a chain
that can skip a tooth in that small area, you know.

Let me know what you decide on for your ride.


Pookybear
 
#8 ·
Snakepit,

In the USA Give Mitch Klempf a call (507)374 2222.
It was listed in his online catalog as part # 37-7072/3
Four bolt t140 43 tooth sprocket.

For the UK, I got mine from Triumphtwinspares.co.uk . They
had a listing on the Ebay UK site and I got lucky they were
willing to ship to the US. I would think that they would have
more on the shelf as well.

Pookybear
 
#9 ·
Well everyone,

I have driven my new setup the 20 43 all weekend. It was
very hard to get off of the bike. Everything from in town
driving to on the highway is much better. On the highway
it no longer fells like I am trying to lauch the space shuttle into
orbit. It ends up being just a nice steady, and smooth
acceleration up to speed. In town, I do have to shift the
transmission now, instead of the geting to 35mph and shift to
fifth and leave it there.

All in all very pleased,

Pookybear
 
#10 ·
Hi Pookybear,

Thanks for getting back to me, i am now going to go with 43 teeth on the rear, i think this will be in a few weeks, i have now got another issue with an oil leak from my front pushrod tube at the bottom, so i will be stripping the topend and replacing the tappet block seals as well as the tubes and tube seals, the previous owner put some none standard tubes on and they look good but don't do the job, so i will do the sprocket as i do the topend.

The joy's of a Triumph, we love it realy, my thoughts are "if i wasn't doing this i would only be doing something else!!"

Once again thank you and i will keep you posted on my thoughts once i am back on the road.

All the best Simon.
 
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