Wondering if anyone can help:

I have an Atlas motor. I know that the tach drive is a 2-1 ratio, and runs a 2-1 ratio tach.
I recently acquired a nice brass 1-1 ratio tach drive that I would like to use. Does anyone know if I can use that with the Atlas motor? What ratio tach would I need to use? I haven't seen a 1-1 ratio Smiths tach.
Are the brass ones used with the chronometric tach?

And help, advice or suggestions would be greatly appreciated.
Thanks
Jeff

Google Joel Levine in Atlanta.

He can rebuild any meter to any spec.

Like new.

a 1:1 tach drive would run a 4:1 tach.

I have a 1:1 drive on my Ranger and a 2:1 tach, so my tach registers 1/2 the actual RPM.

Atlas, Mercury and Hybrid motors ran the 2:1/2:1. Early Commando ran the 1:1/4:1

Atlas tach drive should be stamped 1508/05 on the body, and Commando should read 1508/06. Matchless G80 and G12 ran the /05 box, same as the Atlas.

Hope this helps

Grand Paul,
Thanks for the information. I emailed Joel Levine, and he said that he was unable to do anything with the tach drive. Sounds like he only rebuilds gauges.

Bill,
Thank you also for the advice. That actually works great. Grey Face Smiths tachs are fairly readily available, so acquiring one of those shouldn't be a problem. And that's the gauge that I was hoping to be able to use.

Stupid question: Does the first number in the ratio stand for the drive side of the unit? And the second number indicate the cable side?
Also, does the motor turn at half the rate?
Just wanted to have an understanding of it all.

Basically, this is all good news as I definitely like the brass tach drive. So being able to use that on the Atlas motor with a grey face tach is a perfect scenario for me.

Thanks again,
Jeff

As I understand it, the first number is the output ratio, so with a 4:1 tach, the drive cable spins at half the speed of a 2:1 tach.

The tach drive runs at half engine speed, since it runs off the cam and the cam runs at half crank speed