Speedo drive
Posted: Sat May 22, 2021 8:14 am
I have a question about speedo drives;
I built a 1971 450RT from parts (which didn't all come out of the factory on the same bike); as I wanted to use this on the road, I used a Monza Jr front hub with a speedo drive. I also used a 60mm Smiths speedo (as used on my 250D).
I found that the speedo was reading slow, and the recorded mileage was low.
Now the speedo relies on a 2:1 drive from the hub, but when I measured the ratio of the drive at the wheel, it was more 1.7:1.
It then dawned on me that the Monza Jr has 16" wheels, which would explain the difference, 16" wheels having to turn more times per mile.
So my question is (finally!) is there a 2:1 drive from another hub that I can fit to the hub I have?
I'm guessing yes, since the later RTs had a speedo fitted, but does anyone know for sure (before I part with money)?
Was it only the Monza Jr that had a 1.7:1 drive?
I'm also looking out for a 450 sprocket carrier with two bearings in which was fitted to the RT - mine has only one bearing - must be from another model.
I built a 1971 450RT from parts (which didn't all come out of the factory on the same bike); as I wanted to use this on the road, I used a Monza Jr front hub with a speedo drive. I also used a 60mm Smiths speedo (as used on my 250D).
I found that the speedo was reading slow, and the recorded mileage was low.
Now the speedo relies on a 2:1 drive from the hub, but when I measured the ratio of the drive at the wheel, it was more 1.7:1.
It then dawned on me that the Monza Jr has 16" wheels, which would explain the difference, 16" wheels having to turn more times per mile.
So my question is (finally!) is there a 2:1 drive from another hub that I can fit to the hub I have?
I'm guessing yes, since the later RTs had a speedo fitted, but does anyone know for sure (before I part with money)?
Was it only the Monza Jr that had a 1.7:1 drive?
I'm also looking out for a 450 sprocket carrier with two bearings in which was fitted to the RT - mine has only one bearing - must be from another model.