The International CBX Owners Association

Just a couple times on my 82, so, occasionally, between 5-6,000 revs the voltmeter needle goes crazy, wiggling left and right over and over almost all the way. Normally it’s rock steady at just a tic over 13. It sometimes wiggles just a few degrees but twice now above 5,000 revs it goes nuts! What’s even more weird is when I pull the clutch in, same speed but just idling, the needle stays where it should, rock steady at 13+. Release the clutch, the revs rise and the needle goes nuts. Some miles later I stopped for gas and when I got back on the road and for the next 150 miles it worked perfectly. All the gauges were rebuilt/refurbished by Mr. G so I doubt the gauge is wonky. The Alt brushes are good BTW and the charging system seems to be working properly. So, any thoughts? Just a glitch? I’m prepping for a six state tour and would like to leave with confidence that I’ll return riding the bike.

How are the cushioning rubbers for the gauges? If they are compressed or worn thru and the gauge housing or bezel ring is contacting the mounting plate, the vibration from the motor can make the needles act erratically.

My tach needle was stopping / hesitating at 5-6k rpm and I found the cushions were compressed and worn allowing the top of the tach bezel to contact the mounting plate leaving witness mark on the plate. Replaced the cushions with new and the hesitation in the needle disappeared.

Steve

I'd take another quick check in the alternator. Make sure something hasn't happened since you last visit in there. Make sure the plug into the wire harness isn't melted, nor the connections from the regulator. Make sure the spring, shims and clutch plates are all in spec and good shape. Look for signs of excessive slippage. Then do take a look at the brushes.

Your voltmeter has all the signs of intermittent charging from worn brushes or issues with any of the other things mentioned above.

Dave

I had t he same problem on my 80 CBX. The needle broke off- it was an original one- I performed the coil relay update to send a true 12 volts to the coils- a herdygerdy update, and also made a wire that went right to the voltmeter positive side and never looked back. The problem has not returned and it's been over 5 years.-Mike

80 cbx dude #6216 wrote: Wed May 07, 2025 10:41 am I had t he same problem on my 80 CBX. The needle broke off- it was an original one- I performed the coil relay update to send a true 12 volts to the coils- a herdygerdy update, and also made a wire that went right to the voltmeter positive side and never looked back. The problem has not returned and it's been over 5 years.-Mike

Don’t I have the one from your bike?

SteveG wrote: Wed May 07, 2025 6:42 am How are the cushioning rubbers for the gauges? If they are compressed or worn thru and the gauge housing or bezel ring is contacting the mounting plate, the vibration from the motor can make the needles act erratically.

My tach needle was stopping / hesitating at 5-6k rpm and I found the cushions were compressed and worn allowing the top of the tach bezel to contact the mounting plate leaving witness mark on the plate. Replaced the cushions with new and the hesitation in the needle disappeared.

Steve

Brand new when I had the gauges refurbished.

The voltmeter that was erratic was swapped out with a different voltmeter when the needle broke. The voltmeter and relay update were change at the same time. I did send you the voltmeter from my CBX, however it was not the erratic one that was on my CBX. The issue could be a wiring connection issue or a charging system issue. What is the actual voltage at the battery when your bike is in use? Could you confirm with a voltmeter that there is an erratic voltage issue when it occurs? All voltmeters are calibrated at 13 volts, give or take. These voltmeters are not very accurate. More so for a comparison. If I tip the voltmeters while calibrating I can get the voltage to change. Let me know what you find. If you find the problem is in the voltmeter, I will gladly swap it out.-Mike

As you see, reading my initial post, it’s only happened a couple times and then only above 5,000 revs. Pull the clutch in and it stops. Turn the motor off, get gas and take off and it works perfectly. I thought it might be air getting inside but pulling in the clutch and maintaining speed, it stopped. Return to revs above 5,000 and it goes wonky. There’s no way to test anything while it’s happening and lowering the revs or turning the motor off and on cures it so….i am perplexed.

Looking at the wiring diagram, there is a black wire with a brown tracer (bl-br) going into the gauges, the smaller connection with 4 wires going into the plug. This is the wire that needs to be checked to see if there is a voltage variance. Back probe the wire there and see if the voltage changes. This may be difficult to perform, but with a little creativity, I'm sure it can be done, safely as not to interfere with steering .