Tach very slow

Hi guys,

I'm looking for a little help with my tach. I bought a 83 xj650 maxim. The tach worked fine for a months or so. It's very slow to respond. I opened it up and lubed it up a bit. It seems to be moving freely. I checked the wires and they all seem to be connected. I have searched around on here and can't seem to find a fix. I did read something about resistance playing a role. I have the BPR7es plugs in now because I couldn't find the BP7ES plugs. Is there any way those could mess it up? I am new to the working on bikes thing so you'll have to forgive me.

Thanks!

 

We don't have to forgive you.....

Welcome! The tach is driven off the primary side of the coil, so the plugs shouldn't matter. How does the bike run? If it runs well, you should check the wiring from the tach down to the harness where it ties in after the TCI. This wire should be orange. If that's all good, you may need to replace the tach.

 

your tach is wired into the gray wire on the primary side of your coils and tci it measures the pulses from tci to coil I do not think increasing your resistance 5k ohms per plug on the secondary side of coil . your plug caps are also 5k ohms each. you could change them to non resistive caps to return to the proper rating
their in the xj4ever catalog about 3/4 the way down http://www.xjbikes.com/forums/threa...ection-d-electrical-system.44641/#post-395211
see the note about new wire sets
xj4ever will also have the proper plugs

has your speed been affected?
item 13 Coil and 14 Tci on wire diagram gray wire with dot is the tach

 

I edited my post but 550H is correct. Not sure why I thought the spark plug side of the coil was primary.

 

Thanks guys. I'll check out some more of the wiring. Bike runs great and speed hasn't changed.

 

Tachs can get tired and fail. I have two dead ones myself. One day I'll get bored and diagnose/repair them.

 

Haha, I'm considering just moving onto other projects K-Moe. I don't need it but it's there so I want it to work (if it doesn't take forever to fix).

 

Mine is doing the same thing. It seems like the bearings for the needle shaft are too tight. I lubed mine and its better but still slow. Thinking of trying ATF and acetone on the shaft with Qtip and working the needle a but to see if it will loosen up.
When it gets hot from sitting in the sun it works even better, have you noticed that?

 

Thanks again for all the tips. I think I'll try to take it all apart and clean it up really good and trace some wiring once the weather gets too cold to ride. Also, mine seems to be slow no matter the temperature.

 

Any luck with freeing up your tach needle? Now that it cold outside my tach is really not moving too good.

 

No, not yet. I've moved onto some other projects with the bike. Let me know if you get yours fixed though.

 

I wound my baby up to about 8000 and the tach stayed there for a while despite bringing my speed back down to 60mph. It just dropped back down when hit about 4500. I am hoping it's just not used to winding up that high. Other than that mine works fine after sitting in barn for a while. I am not a purist when it comes to my ride. Can I buy after market tachs and speedo?

 

I am sure there are aftermarket setup's that people have installed with out much trouble. In any case these old bikes are in need of lube and attention nore than is stated in the service manuals.
Instruments need to be refurbished like any other old car or truck. The problem is there are not many speedometer shops arouund anymore since cars and trucks have been electronic now for years.