Triumphrat

Vince C

How often should a T140's chain and sprockets be replaced? It looks easy enough to change the sprocket at the rear wheel, but what about the smaller one at the gearbox end? What's involved in changing that? It doesn't look easy!

What is a good way to minimise chain / sproket wear? I know from bicycle experience that frequent chain replacement preserves sprocket life, but how often on a Bonnie should 'frequent' be?

pookybear

Hello Vince,

Easy to tell when the sprockets need changing, when damage
occurs or when the teeth become hooked shaped. As for the
chain itself, when you clean the chain and relube see how much
it has streached in lenght.

The original unit on my ride was done in 14,000 miles and needed
to be replaced badly.

And the front sprocket requires you to remove the primary, clutch,
and stator parts from the engine to gain acess to the sprocket.

Pookybear

coloradobob

The number one thing for non-o-ring chains is oil them immediately if they get wet and clean the grit out. WD-40 will drive moisture out but doesn't last because it's volatile. I oil the chain every-other ride and before any big ride. I don't live in a rainy climate, but that's my suggestion because it's possible to oil after every rain. I currently run a Tsubaki 530HSL-NP x 108 chain nickel plate that's holding up well. I've always run Renolds chains for longevity. Bob

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daveforty

For many years my T140 was my everyday bike, and I kept notes in my Haynes manual of servicing etc.

Generally I would get 6/7000 miles out of a chain and change both sprockets approx 18000m or three chains. I have sprocket set changes noted at 18000, 36000, 54000 and 72000 approx.

I did tend to use cheap chains and not be over fussy about lubing them, usually a boil in grease every 1500 when I did an oil change.

Changing the gearbox sprocket does require a fair bit of stripping down but its fairly easy. You will need to take the primary drive completely out to get to a cover plate behind the clutch, then undo a large nut and pull the gearbox sprocket off the shaft and out through the primary case. You will need the special tool to pull the clutch centre off the end of the gearbox mainshaft, a 1 7/8 AF box spanner for the nut on the gearbox sprocket and a puller to get the crankshaft sprocket and gearbox sprocket off - that is a simple tool that can be made from a bit of angle iron.

Probably a couple of hours work at a relaxed pace.