Tachometer ratio

[pipexs]

Hello, I'm looking into dime city's 2.5" tachometers, the question is they offer two ratio settings, a 1.5ratio and a 1.7 ratio. Can anyone tell me what ratio would work with my 81 xs400 special II Yamaha?

Thanks.

 

[BBS360]

The first result when inputting "tach ratio" with quotes into the search box to the top right will have you answer.

 

[pipexs]

Excellent, thanks!