4104 tach sender, elec question

[John Z]

I have found a new sender, but it causes the tach to run twice as fast as it should.

Is it feasible to cut the signal in half using some readily available elec components?

[bevans6]

No, not really.  You'd have to build a frequency divider, which you could do with a flip-flop, but as soon as you get into an integrated circuit design you need to make power supplies and figure out input and output drivers and all that stuff.  I would either find the correct sender, find the correct tach to go with the sender you have, see if there is an adjustment on the tach or sender that you've overlooked, or make a new faceplate for the tach.  Or just put up with it, which is what I would probably do...

Brian

[zubzub]

+1 for "put up with it". Especially with the added bonus.... you now have a super high revving racing engine. 

[TomC]

Sounds like you have a 4 stroke camshaft speed sensor being used on your 2 stroke-making the tach read twice as fast. Just get the proper speed sensor-they're not that expensive. I have a speed generator running off the back of my blower drive for my tach. Works well-just have to run two wires. Good luck, TomC

[luvrbus]

Most electric tach heads have DIP switches on the back of the head to compensate for that,the VDO tachs I buy sometimes will be showing 2000 at idle if I forget to flip the switches

[John Z]

Thanks guys, for the response. I guess I will look for a correct speed sensor, although I had no luck hitting the local truck shops last summer. I had the Speedo out last summer and don't remember seeing any switches on the back of it. Perhaps there was a cover on the back, didn't notice, but worth taking another look.

[chessie4905]

   Get a two to one speed reducer to place between the tach sender and engine. Find a speedometer shop that can make one up for you. Too bad you aren't from Pa. There is one in Lewistown.

http://www.mrspeedometer.com/