911E Tach, 70 vs. 71 & later

[dafischer]

Does anyone know what the difference is between a 70E tach (911.641.302.00) and a 71 and later (911.641.302.01)?

Are they interchangeable?

[dafischer]

Anyone?

[randywebb]

at some point in the early/mid 1970s the electronics changed, could be that point

[Early_S_Man]

Dave,

I don't have info on the specific pn's you posted, but, as Randy said ... there was a change around that time to eliminate the elusive 'Ballast unit' ... a resistive 3-terminal divider circuit that was used with the early tachs vs. the later tachs that were simply triggered by the points!

You probably can't directly interchange them with out wiring changes, but the changes are pretty simple! A later tach replacing an early one is the easiest change ... just move the Black/Violet tach trigger wire to the points input at the CDI unit!

[dafischer]

Thanks for the info, guys.

Of course, I've got the difficult case...70 NOS E tach and 72E needing tach.

[randywebb]

I posted a thread some time ago on this, but I don't hink it will help you. It related to 1973 and later I think.

I guess you could try... be sure to post results for the next person.