Skorpion Rear Sprocket

[Old Dog]

Hi all,
I am interested in what rear sprocket size/tyre combination people are running. My Tour is off the road with wiring difficulties and I am changing the sprocket carrier's bearings, anyone tried this?

I plan to fit a 43t but I am interested in feedback as to how much off the top you lose etc

Many thanks

[Skorpion]

Hi all,
I am interested in what rear sprocket size/tyre combination people are running. My Tour is off the road with wiring difficulties and I am changing the sprocket carrier's bearings, anyone tried this?

I plan to fit a 43t but I am interested in feedback as to how much off the top you lose etc

Many thanks

If my experiance with a Traveller is anything to go by you will increase top speed by about 10mph, using the 43t & 150/60 rear tyre.

The engine is not strong enough to pull max rev's in top gear with the original 39t rear sprocket, also the 43t makes city riding much more comfortable.

A WIN WIN situation

[DAVID THOMPSON]

mine is a 45 and works great as i do a lot of very slow town riding
i also use a non oring chain as the x ring o ring ones seem to snatch and vibrate a lot
and speed limits here are only 55 mph on most roads
so a monster top speed is useless
dave

[pod35]

My Tour came to me with 14/39, but I've not had any other gearing (have a 15 to try). It seems to be all over by 85mph. Then again my bike now has 99,500 km on the clock and I think it needs a rebore plus valve guide seals and possibly valve guides I met up with Tigcraft and his sport a few days ago and we swapped bikes for a run down and up Holme Moss (google it - awesome road) and I noticed a puff of oily smoke when he opened the old dear up on a short straight. I only saw it once because I couldn't keep up

Justin

[pod35]

I've just changed the front sprocket to a 15 and solved a mystery at the same time. Ever since I had the bike it has had a rattle when going over bumps etc. I've investigated the radiator ( rubber mounts stiff and loose), the sidestand and centre stand , the rectifier (which had one bolt missing) but not been able to cure it. Whilst changing the sprocket I noticed that the chain was hitting the swingarm protector right next to the swingarm pivot and though it hadn't worn through it was still making the swingarm ring like a bell. The 15 is just big enough to stop the chain from doing this. I've read things on the net which claim that you shouldn't use sprockets with even numbers of teeth and that small sprockets wear faster and take the chain with them. So in answer to the question that no one asked - don't fit a 14 tooth front sprocket.

Justin

[Bill Jurgenson]

So in answer to the question that no one asked - don't fit a 14 tooth front sprocket.

I don;t know how many times I've cautioned about fitting a 14t cog, certainly not because of the swingarm (tho that is also a reason).
First of all, one should never fit a cog with an even number of teeth; that is simple engineering. Then the stress of the bearing is unduly high and for no reason at all. Then, the smaller cog results in a calculable loss of performance due to its smaller diameter. Thus 15t is not a random choice by the Yamaha engineers.

In my experience, the best all-round setup is 15/43 and I prefer that with a 140/70 rear tire. I have been using this generally for years now, having tried 15/41 and 15/42 as well. A little top speed may be lost but that is of no importance since you cannot legally go that fast anyway outside of Germany. As it is, a stock Sport with the stock 15/39 and 150/60 tire runs almost as fast in 4th as it does in 5th because the engine cannot pull that tall gear. The shorter final ratio makes the otherwise stock bike much more lively.

[DAVID THOMPSON]

15x 45 works for me on the traveller as speed limits where i live are very low
most everything 55 mph or less (88.5 kph)
thats the reason i ride the rt125 most of the time
dave

[pod35]

I will go for 15/43 next time I change chain and sprockets. It will be just a bit lower than the 14/39 which sounds about right.
Justin