2 cyl 2-stroke tacho on 4 cyl 4-stroke?

[unsane]

Just wondering if anyone knows if its possible to use a tacho from 2 cylinder 2 stroke bike on a 4 cylinder 4 stroke.
Just put a KR1 tacho on my gpz 1000 and getting some weird results.

First the tach would die and motor would start sputtering if i used the front brake. Disconnected the brake switch and all seemed good.
Then i noticed the tach seemed to be reading at about 1/2 actual revs (like idle at 500rpm instead of 1000). Any ideas on how to get it reading the real revs (basically to double the reading)?

[Rocket]

The brake light switch is a bit of a worry ! WTF does that have to do with coils ??!!

I would imagine a two stroke gets twice as many pulses for a set rpm than a four stroke so it would read half speed on the four stroke.

[Rocket]

Assuming that the ring ding uses one coil only for two pots.
Which means it fires every 180 degrees.
Whereas a on a four stroke with the coil running two pots (one coil per two cylinders on a four cylinder) would fire every 360 degrees.

[alfiestorm]

quote:Originally posted by unsane

Just wondering if anyone knows if its possible to use a tacho from 2 cylinder 2 stroke bike on a 4 cylinder 4 stroke.
Just put a KR1 tacho on my gpz 1000 and getting some weird results.

First the tach would die and motor would start sputtering if i used the front brake. Disconnected the brake switch and all seemed good.
Then i noticed the tach seemed to be reading at about 1/2 actual revs (like idle at 500rpm instead of 1000). Any ideas on how to get it reading the real revs (basically to double the reading)?


I think i would be very worried about the front brake light switch having that affect, does it do it with the rear brake light switch as both switches are on the same circuit.
The only way I can think the brake light circuit would do this is it is draining the power away from the ignition circuit which would lead me to the battery and charging circuit
1, Test brake switches front and rear
2, Test battery, What does the voltage in the battery drop down to when you press the starter button and what is it when the bike is running on fast idle should be above 13.4vdc and not above 15.2vdc
3, Test charginging circuit for correct output for your bike
4, Bin or sell the 2 smoke tacho and get a 4 stroke one.