Hi I'm redoing my spare box and refiting a new sprocket the old ones a bit worn. I ordered a new one from dragonfly but this one only has 18 teeth the worn one has 19 i ride with a sidecar anyway will this make Mutch difference sorry about gramerregards Martin

Lowering the gearing by a single tooth on the c/s sprocket can't hurt, especially since you are toting a sidecar.

Depending on the weight of the car, you may find it an improvement, with the bike a bit more responsive. I can't imagine that the current top end speed will suffer, and may possibly, slightly, increase with the drop in sprocket size....just a guess.

JDE

email (option): teladelujo@ msn.com

I have an 18 and a 19 tooth sprocket 1 is a bit worn I can email you some photos and you can have them for nothing if you are a uk resident

email (option): roger.beck@node6.com

just take care; i've had to change the gearbox sprocket on mine, bad machining left a radius on the inner edge which rubbed on the box casing...
and a brand new 19t was fractionally undersize on the inner dia, so it wouldnt fit !

email (option): chris.astinbarker@btinternet.com

Hi Martin,

I have a BSA WM20, original 500cc with a metal sidecar.
I use 18T sprocket now, but before it, I had 21T (!)

Once, when I opened up the covers in order to replace the clutch plates,
I saw it and changed it to the original 18T.

The difference was huge!
The 21 was very "calm" and long, while with the 18T I can get to 4th gear
In a matter of 50 meters..

If it was easier to replace, I would go back to 19T at least.
If yours is made of light fiberglass,
It almost has no affect on starting on 1st gear.

I have another WM20 with a fiberglass sidecar, and what a difference !
You can hardly know it is there.
Unfortunately, I never open the clutch cover there to count the teeth.

BR,
Noam.

email (option): noam10@gmail.com

The sidecar is a watsonion ascot quite heavy the new sprocket is absa part so should be good fit any way il suck it and see thanks for tips and offers kind regards martin