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Changing rear sprocket / gearing (Read 3633 times)
John(Guest)
Ex Member



Changing rear sprocket / gearing
02.08.04 at 16:09:00
 

Ok, only had the TR1 a few weeks, first one I have ever owned or ridden,  did a 200 mile ride back from the guy I bought it from to my place.
Having ridden most things over the years (last bike was an '81 xs11 special) I wasn't new to v twins, just new to japanese ones mebbe, anyway, the motor felt way too revvy for my tastes, so time to mess with the gearing.. (the xs11 was too low geared too but being a shafie there was no cheap or easy solution to that one)
So, standard gearing is a 16t on the front and a 35t on the rear in 630 chain. mine has long since had the chainguard removes and so was running an O ring chain, it wasn't worn that much but it was dirty and sticky, so might as well do that too...
I opted for a 29t rear sprocket, only way to do this was have a custom one made up which was dead easy to arrange, just ask for a 29t in 630 chain and from memory 844 pattern mounting bolts, cost me 30 Uk pounds.
A good quality new heavy duty o ring chain in 630 set me back a painful 85 uk pounds, I was starting to miss shaft drive....
On the road this completely transforms the bike (it is set up with a solo saddle only and I don't weigh much myself) it takes a little more clutch on take away, a gentler throttle on low rpm town driving so the rear wheel cush drive can absorb the pulses, and pretty much forget using top gear around town except for the odd straight bit, but she is still extremely manageable and docile.
on the open road however a total transformation of the bikes character, from a revvy little thing that sounded and felt unhappy, it now feels like it has long legs and enjoys running, much much much more like a moto guzzi 1100 sport or a nicely set up vincent, there is still all the acceleration any reasonable rider could need on the road, and a significant boost to fuel economy.
If you don't always ride two up, if you weigh less than 85 kilos, if you don't spend all day doing less than 40 km/h in town, seriously consider this mod, the only way I can really describe it is by saying it's like the standard yamaha gearing was set up for riding with a sidecar bolted on, and now it is back to a sporting solo with long legs, the way a v twin ought to be.
cheers

 
 
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Larry Polistina(Guest)
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Changing rear sprocket / gearing
Reply #1 - 10.08.04 at 16:35:00
 
John....Do you know if the 29T rear sprocket will fit inside the "chain enclosure"?
Larry

 
 
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John(Guest)
Ex Member



Changing rear sprocket / gearing
Reply #2 - 10.08.04 at 18:28:00
 


 
 
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John(Guest)
Ex Member



Changing rear sprocket / gearing
Reply #3 - 10.08.04 at 18:45:00
 
While I'm at it, don't forget to make sure your sprockets do NOT divide equally into the number of chain links....
I'm guessing I'm running either 98 or 100 links of 630 chain with my 16t front and 29t rear.
98 links
98 / 16 = 6.125 so every 8 chain revolutions the same front sprocket tooth meets the same chain link.
98 / 29 = 3.3793103448275862068965517241379 so that's perfect
100 links
100 / 16 = 6.25 so every 4 chain revolutions, not so good
100 / 29 = 3.4482758620689655172413793103448 so again perfect
standard is what ? 104 or 106?
104 / 16 = 6.5 so every 2 chain revolutions, not good at all
104 / 35 = 2.9714285714285714285714285714286 so perfect
106 / 16 = 6.625 so every 8 again, not too bad
106 / 35 = 3.0285714285714285714285714285714 so again perfect
so mr yamaha didn't use any brain cells when specifying a even tooth primary sprocket, because when .....
a = no teeth in sprocket
b =  no links in chain
c = b/a
c = a low fraction, eg 1/2 or 1/4 or 1/8 etc that's not too good because it means UNEVEN chain wear, eg not all rollers wear at the same rate, which is bad and can easily cut chain life by 75% in an extreme case.
my current 29t rear and standard 16t front gives a ratio of 1.8125 so if we want to maintain that ratio and go for a custom front sprocket with a proper odd number of teeth, eg 15 or 17...
15 x 1.8125 = 27.1875 so a 27t rear
17 x 1.8125 = 30.8125 so a 31t rear
please remember changing sprocket sizes = changing overall chain length so you have to factor / guesstimate this in when doing your sums.
HTh etc

 
 
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Lars Sandström(Guest)
Ex Member



Changing rear sprocket / gearing
Reply #4 - 25.09.04 at 14:23:00
 
The temperature aspect seems a bit exaggerated. From an old TR1-test I read that the temperature newer exeeded 70 degrees Celsius even during hard and long riding. By the way, the TR1 has 2 cuschdrives, one in the gearbox and one in the rear hub.
The ideal would bee if someone manufactured a cain-enclosure that was a bit smaller...

 
 
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