tach problems

[b1rks]

Took my XS to work like normall. Started no problem {new battery} Cold day up here in Canada frost weather. Noticed my tach would not move over 2000. Is this an indication of a alternater isssue, Bike startes allright lights all working fine. Any suggestions would be appreciated.

[TopCatGr58]

Hate to ask, but WHY a new battery? Did you test your charging system BEFORE getting the new battery? The tach reads impulsed from the ALT, and so IF it's not charging, it won't work. You can run the bike for a while on a FRESH battery, hence the ability to start, and lights....are you sure the headlight was working?

Check the charging system with a voltmeter, should get up to ~14.5 volts at 2500 rpm, if so...then you may have a bad tach!
But also try cleaning the contacts for the wires for the tach!
Cold weather can gum up the oil/grease inside the tach??
T.C.

[COOL TOM]

Tach

My tach on my XJ does not work when cool or cold but after i ride it about 10 or 15 min it starts to work. I don't think it is the alternator because i have been riding with this battery for 2 years now.

[b1rks]

got the battery bout amonth before alternater problem. Bike ran fine far as electrical. Tach is getting some juice, enough to push it to 2000. Just wondering if anyone else experienced same issue. Anyways I need a new Speedometer to it went down last year {cable fine speedo problem.} Hello Ebay.

[84xj1100]

Just thought I'd chime in here folks.........riding in Winnipeg from end Mar - mid Nov, I have a tendancy to encounter a little cold weather.

Both my bikes do exactly the same thing....depending on just how cold it is - my tach will take up to 15 km's ish to "respond" normally. More specifically, they may not even reflect idle rpm initially....then as I increase speed & rpm ramps up, the tach needle will be sluggish and may hover around 2000 rpm until I reach a stop light....then it winds down to 1100 rpm. Once I get on the highway (typically speeds that would reflect 4000 rpm) the needle will continue to rise.

Once 10 - 20 kms goes by (depending on how cold it is) the tach then responds normally.

I have encountered this "phenomina" ever since I bought the first bike (original owner) in 1985 - bought the second bike three years ago & it does the same thing.

I have never tried to diagnose this with a multi meter so unfortunately I can't offer any concrete explaination.

I guess it's just the price we northerners pay for operating here in the arctic.

[randy]

Last year I installed an NOS tach on my 79F and I'll be damed but it's needle jumps just like the original one did. I've been all through the wiring, and could never figure out what was causing the jumpiness.

Now I'm thinking that maybe it has something to do with the feed from the stator, maybe a slight voltage back-feed or harmonic craeted by some out-of-phase EMF.

This winter I'm going to try adding a diode on each white leg from the stator and if that does nothing, then I'm going to try moving the whites around on the connector, re-phasing the stator and see if that cancells out the (assumed) harmonics.