Tach issues

Hey guys running aftermarket TACHS. I be been running this one for about a year now and have good and bad luck with it. Sometimes it'll read correct and other times swaying or not at all. Its has settings for 2,4,6, or 8 cyl. Typical 4 wire hook up. Red, blk, green and white. Green is tach signal hooked up to 1-4 coil running in 2cyl.
Its just aggravating that its not consistent.
Any input is appreciated.
Thanks and good day.
Mike

Well its not letting me load pics. anyway its a sunpro super tach 3. Look in my build in projects. There should be a pic of it in there.

There really are only two things it could be and both of them are loose wires. There have been a few people here with electronic problems that resulted from some of the solder joints in the headlight shell oxidizing and crumbling.

The fact that it works sometimes tells us that it's connected right - now to address the intermittent nature of the problem. The green wire should be checked to make sure it's making a good connection at the coil. The rest should be checked for continuity as well.

What kind of connectors did you use to hook it up? If I was a betting man, I'd guess the 3M vampire crimp connectors. If that's the case, check those - I don't like them in weather-vulnerable applications. With the bike running, jiggle them and see if one or more of them pulls loose. I'm gonna guess that you're losing the red (power to the tach, right?) wire. If you were losing ground, the light would flicker, and the white (I'm guessing) is the dimmable light connection, so it doesn't play into the correct operation of the tach.

I used to have problems with electronic drive tachs on cars. Sometimes it's because ignition noise gets into the lines and causes false triggering. If your bike has no resistor wires or caps, it may be putting out enough electronic noise to cause the tach to read goofy.

I use a Sunpro Super Tach II. It's the third one I've had. The first two lasted about two years each. On the thrid one, I took it completely apart, and siliconed all of the components and loose wires. it has lasted over 10 years now. When I took the dead ones apart I found vibration had caused traces and parts to develop cracks. One of tem also had the needle fall right off.

These things are not meant to handle the type of vibration a bike puts out, versus the interior of a car.

Oh, and they are not meant to come apart. I had to cut them open with a knife and re-sealed the third one wth glue etc.

loudhvx wrote: I use a Sunpro Super Tach II. It's the third one I've had. The first two lasted about two years each. On the thrid one, I took it completely apart, and siliconed all of the components and loose wires. it has lasted over 10 years now. When I took the dead ones apart I found vibration had caused traces and parts to develop cracks. One of tem also had the needle fall right off.

These things are not meant to handle the type of vibration a bike puts out, versus the interior of a car.

Good point.

I built an electronic ignition back in 1980 for my KZ750 and mounted it to the frame.... DOH!!!!!

I had components fail from vibration about six times. I finally wrapped the thing in foam rubber and stuffed it in the plastic tail section and it stopped dying.

Thanks for the input guys. I've got this weekend off so I'll do some testing. Got another wiring issue now.. My tailight quit working on run but comes on in accessory..??? I don't get that one at all.