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Tach woes

2568 Views 7 Replies 4 Participants Last post by  57ChevyZZ4
Installed an AutoMeter 3 3/8" tach on the handlebars that worked perfectly for several mos. Originally connected hot/grd to guage harness and tach to factory wire on the left side of the frame. While driving it developed a flutter and the needle fell off. Mtn BH (great as always) sent me a new one but the flutter remained. The tech support at AutoMeter suggested a 50K pot in line. That didn't have any effect regardless of resistance. They then sent another tach as they said there was a design change and that they had some needle problems. Still flutters. Ran the ground to the frame. Ran tach wire direct to the dist., tried hot direct to the battery. It even flutters (around 0) with the motor not running as long as the ignition is on. It will stop only when the power source is interrupted to the dist. (h/bar on/off switch, fuse second from bottom on rt side removed, + or tach wire at the dist disconnected). I replaced the coil, module, condenser with harness with no luck. Any suggestions. I'll check my email when I return from anger mgmt class. Conrad
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Tach Woes

My first approach on a nasty problem like this is to isolate the problem. You have lots of variables.

I'd first work on the big picture and find out if it is the bike or the tach. Beg, borrow or steal a Tach from a different manufacturer. Disconnect your tach and connect the test tach to the same wires. If the problem disappears, you know the Tach is the problem. If not, we know we need to start trouble shooting the bike wiring.
I just picked up a cheap Sun tach and it doesn't seem to flutter. Couldn't believe I had three bad tachs. Possibly they don't work well with the HEI distributor. It's a ProCycle rather than the standard car model but I'm sure MBHC has sold a lot of them with no problems. Thanks for your help....Ill let you know what happens. It's raining now and can't ride to check it out. The problem has been worse under load, more so than free revving. Conrad
cstraube said:
Possibly they don't work well with the HEI distributor. It's a ProCycle rather than the standard car model but I'm sure MBHC has sold a lot of them with no problems.
I've got a ProCycle #19302 on my bike, and it doesn't flutter. But it shows twice as much revolutions than the engine really turns. That's because the ProCycle serie is made for 1 or 2 impulses per revolution (2 or 4 cylinder) - but our V8's make 4 ignition impulses per revolution (8 sparks every 2 crank revs)

I sent Autometer an email, and they answered that there isn't a simple switch in these ProCycle tachs to make it work for an 8 cylinder engine, and that I have to send the tach back to the factory (Autometer) for recalibration - which would be about 45 USD + shipping.

A friend of mine is currently working on a solution. He's working on a electronic impulse splitter . I hope this will make it work properly.

Where did you bought your's?
Did it show twice revs than real like mine?
If so - what have you done?

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Oh, sorry - I should read your messages completly before I ask questions :oops:

You bought your's at MBH. They sell them recalibrated. Wish I would have bought mine there, too.
I tried to save a couple dollars, and bought it (new) in Ebay. :cry:

Sorry for the delay, just got home. Yes, I got it from MBH already calibrated as well as the one from AutoMeter that they replaced. It registered correctly, just developed the flutter (severe at times). Enough to knock the needle off once. The mystery is why it worked perfectly for several months then have two more bad tachs. Gotta believe there is more. I'll let you guys know more tomorrow. By the way, MBH and AutoMeter have been great to work with. Everyone has been more than willing to help.
Just FYI. I changed to another brand and the problem solved. Thanks for the help.
Tach problems here too

Just got my '05 BHC-9 ZZN trike and most everything works but the tach. When I turn the ign key on, all the gauges do a quick test "bump" but the tach gauge seems dead. Checked the Red/Black DC power wires with a multi-meter and they get power when the switch is on. Sound like a bad tach?

Answered my own question. - a bad tach. New one installed and I added a foam plug under the dash gauges to prevent heat from the engine to cause the condensation that caused the tach to go bad in the first place.
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