[R100ELL]

Firstly forgive me as I’m sure this has come up before but hoping someone will be able to help me on this one. My tachometer is slow to respond and I was previously advised to put oil/lubricant down the side of the hole where the cable goes in. I also blew air from a compressor through it in the hope there was anything like dust/cobwebs or something else like that.

None of these worked so I decided to get another tacho which arrived today. I tried it and it was the same so went through the above process and still running slow. I haven’t replaced the cable yet but out of the tachometer it is turning and fast when I throttle up.

Does anyone have any other thoughts on what else to do or try?

I do have an Ignitech unit and know I could run an electronic one from it, is there any option to put an electronic in the old tachometer housing so it at least looks original?

 

[DouginEasternWashington]

I would’ve replaced the cable before the tach gauge. It’s most likely the original cable. At minimum clean and lube it but when I had problems with the tach I just replaced the cable and have had no problems since.

 

[R100ELL]

I would’ve replaced the cable before the tach gauge. It’s most likely the original cable. At minimum clean and lube it but when I had problems with the tach I just replaced the cable and have had no problems since.

That would’ve been the smart thing to do but for the life of me I thought well it’s turning and when I rev it up it turns faster so I thought that means it’ll be fine. I have lubricated it now but I was kind of hoping it wasn’t the cable as I am sure it’ll be a nightmare to try and change it without taking the radiator and such like off.

Would a duff cable make the needle go up and drop slowly?

 

[Randall-in-Mpls]

Have you tried grabbing the end of the cable while it's turning? My guess is that it's broken internally, and only turning due to friction.

 

[Randall-in-Mpls]

A dry or dirty cable can't turn any slower. It's gear driven, and there's nowhere for it to slip. It will only break sooner.

 

[R100ELL]

Have you tried grabbing the end of the cable while it's turning? My guess is that it's broken internally, and only turning due to friction.

I could give it a go. Daft question but if for some reason it isn’t broken how much force should I put on the end of the cable when grabbing it so as to avoid spinning my fingers off 🤪. I take it if it is broken it’ll stop spinning easily enough.

 

[Randall-in-Mpls]

If it isn't broken, it will slip between your fingers. You'd need a good grip with pliers to resist it.

 

[DouginEasternWashington]

When I replaced my cable my problem was my tach not being accurate. When cold the tach would read fine but after a few miles the tach would only go up to around 5000 when I knew the motor was revving higher. The old cable wasn’t broke. A bad cable can do funny things that don’t make any sense. Yes you will want to remove the radiator to replace the cable. Probably the fan too. All easy peasy to do.

 

[Randall-in-Mpls]

Because it's a wound spring inside the cable, the end could be held up by a dirty sheath, but only for so long. Eventually, it will either overcome the resistance and unwind, or break. I can imagine the needle jumping around in that scenario.

 

[Randall-in-Mpls]

All easy peasy to do.

Assuming you can get the retaining screw out. It's a JIS cross head (not Phillips!) with an awkward reach. I was stripping parts off a scrap engine this weekend, and that screw wouldn't budge. I haven't tried the torch yet, but I know it will be a fight.
It's a good idea to replace that screw with a hex or Allen head.

 

[DouginEasternWashington]

Because it's a wound spring inside the cable, the end could be held up by a dirty sheath, but only for so long. Eventually, it will either overcome the resistance and unwind, or break. I can imagine the needle jumping around in that scenario.

Well, my tach acted that way for months and several thousand miles. Like I said, a bad cable can do things that don't make sense. The speedo cable is acting up on my bmw r100rt. The needle jumps around and will read wrong at speeds above 70 mph. The cable isn't broken and was this way all last summer. If the spring cable eventually catches up, why is my odometer off too? I had the same thing happen on an old chevy van and had to change the speedo cable because I got paid mileage for the job I had at the time.

 

[PaulinIowa]

Thinkin I'd go with a new cable, just sayin....

 

[bahn88]

Assuming you can get the retaining screw out. It's a JIS cross head (not Phillips!) with an awkward reach. I was stripping parts off a scrap engine this weekend, and that screw wouldn't budge. I haven't tried the torch yet, but I know it will be a fight.
It's a good idea to replace that screw with a hex or Allen head.

Its an awkward position, so as well as needing a longer JIS driver to reach it the screw, you may want to avoid using an impact....
is just replacing the cable inner an option?

 

[DouginEasternWashington]

Its an awkward position, so as well as needing a longer JIS driver to reach it the screw, you may want to avoid using an impact....
is just replacing the cable inner an option?

I wouldn't replace just the inner. It's always an option, but one I never recommend or practice. I've had great success getting that screw out with a 1/4" ratchet with the JIS bit. I love that 1/4" ratchet set and use it all the time for stuck fasteners that require a screwdriver bit.

 

[bahn88]

And if that oil seal is leaky on tach cable removal and inspection (youll probably aim a torch in there)....that will provide more fun.......

 

[DouginEasternWashington]

Assuming you can get the retaining screw out. It's a JIS cross head (not Phillips!) with an awkward reach. I was stripping parts off a scrap engine this weekend, and that screw wouldn't budge. I haven't tried the torch yet, but I know it will be a fight.
It's a good idea to replace that screw with a hex or Allen head.

As far as I know there are no Phillips screws on any part of our motorcycles unless a previous owner added one.

 

[bahn88]

without being pedantic...lol...its a JIS screw but if you bought your drivers in the last 10-15 years (Japanese brands such as Vessel included) they'll be "JIS compatible"....as many brands no longer label their drivers as "true JIS"

 

[R100ELL]

Well after a bit of fettling I think it’s resolved. I tried to grab the cable and no joy, couldn’t keep hold or stop it turning. I had fired some cable lube down it so that might’ve helped. I also cut a nail down that had a square(ish) end on it and used it on my drill into the tach cable receptacle on the tachometer. I managed to get up to 8,000 rpm, that’ll probably be the last time that’s going to be up there 🤪. A bit lubrication and it looks like all is well........so far.

Stuck it back on the bike and no longer running slow for now at least.

 

[bahn88]

if its solved great...
After all...... the more things are "dissected" the more likely you'll need NLA parts or many hours of time.

 

[Sidecar Bob]

is just replacing the cable inner an option?

You would have to get the inner cable out to do that anyway and it has to come out from the end at the engine.

In a pinch you could swap in the speedo cable for testing but that is awkward when the rad is in the way.