Tach or Alternator that is the question

[MSG Groves]

I recently purchased a 1993 FJ1200.  It's really a nice bike.  However, it did have a couple of problems. It wasn't charging correctly and the tach was reading double what it should.  I took it to the dealer as I'm not the greatest when it comes to motorcycle repairs.  The dealer put in a new voltage regulator that took care of the charging problem.  They indicated on the invoice that the tach was ok.   but, as I was riding home I notice that the tach was still doubling.   I took the bike for a 100 mile ride just to see what would happen, it ran great and at one point the tach actually settle down and read the correct RPM's for a short time.   When I call the dealer back that couldn't tell me if the tach runs off the alternator or the coil.   I actually called three different dealers and all were the same "clueless".  Can anyone out there give an old veteran some insight on this problem? 

[simi_ed]

Tach is fed from the coils.  It has been suggested that a bad coil ground will cause you tach woes.  Mine started after I added the electronic cruise control.  It is also aggravated by low battery voltage, such as at idle after start-up.  Never really goes away for long, and is only noticeable below ~3k rpm.
My 2¢

[MSG Groves]

Ed, Thanks for the feedback.   

Think I'll try to pull everything apart this weekend and check all of the connections.   

Again, thanks for your help.


MSG G

[MyFirstNameIsPaul]

My tach intermittently goes from correct to wildly high, usually for long periods of each.  I completely rebuilt my entire ignition system from the battery on up, so I'm quite certain I don't have a ground.  I tore apart my dash and couldn't find anything that looked out of place.  It happens in cold weather and hot weather.  It happens in torrential downpours and when it's bone dry.  I have given up on the whole affair.

[Dan Filetti]

My tach intermittently goes from correct to wildly high, usually for long periods of each.  I completely rebuilt my entire ignition system from the battery on up, so I'm quite certain I don't have a ground.  I tore apart my dash and couldn't find anything that looked out of place.  It happens in cold weather and hot weather.  It happens in torrential downpours and when it's bone dry.  I have given up on the whole affair.

Paul-

You have stock coils then?

I wonder if anyone (Rich I'm +/- refering to you) has been able to correct/ reproduce this behavoir after coil replacement.

Seems like there been a rash of this happening, sure would be nice to get to the bottom of what may be causing it.

Anyone?

Dan

[MyFirstNameIsPaul]

I have all Dynatek components.

[MSG Groves]

I took the bike out today, and the tach was right on the money.  The temp has dropped to around 70.   I was talking to a friend of mine that's really in to cars and bikes.   He said that since the tach is running off the coil and that it arrears that the temp is directly related to the problem it is a ground problem.  This guy is Mr motorhead.  He said that as the temp rises the resistence in the coil will increase and if the ground is not perfect is will case the reading to go nuts. I going to tear it apart next week to see what I can find.

[racerman_27410]

I took the bike out today, and the tach was right on the money.  The temp has dropped to around 70.   I was talking to a friend of mine that's really in to cars and bikes.   He said that since the tach is running off the coil and that it arrears that the temp is directly related to the problem it is a ground problem.  This guy is Mr motorhead.  He said that as the temp rises the resistence in the coil will increase and if the ground is not perfect is will case the reading to go nuts. I going to tear it apart next week to see what I can find.

there is a coil ground right at the coils mounting location..... doing a thorough cleaning in this area may just fix your problem.


KOokaloo! 

[thkfast]

I have the same problem and posted on General Discussion, but this is where I belong!

I removed the tank, tightened the ground connection at the mounting point of the coils.  NO LUCK.

Then I re-removed the tank, removed the nut/bolt that hold the coils in place, took sandpaper and
steel wool to clean them up, even turned the nut/bolt around and tightened it real tight.  NO LUCK.

Then I thought there might be an unnecessary drain on the battery, so I removed an auxilary plug
I had connected to the battery posts.  NO LUCK

It reads 2,000 rpms at idle and 7,000 rpms at 35 mph in 2nd.

Here are photos of of the area I was working around...any more suggestions of what I should try?





and if that's not where I need to be checking, here's the ugly side of the bike...

[SlowOldGuy]

I removed the tank, tightened the ground connection at the mounting point of the coils.  NO LUCK.

Then I re-removed the tank, removed the nut/bolt that hold the coils in place, took sandpaper and
steel wool to clean them up, even turned the nut/bolt around and tightened it real tight.  NO LUCK.

That's not the correct ground.  That's just an external ground to prevent a shock in case the coil shorts out internally.

See those connectors up near the steering head?  Two of them are coil connectors, the other one is the ignition connector.  Make sure their contacts are clean!  This is also where you would measure the voltage getting to the coils.  According to my wiring diagram, one coil connector has an orange wire and the other has a grey wire (both connectors have the red/white power wire).  The orange and grey wires are the ground side of the circuit which is switchd by the ignitor in order to fire the coils.  The tach reads the signal on the grey wire.  Chase that wire as far as possible.  I would suspect it has a loose connection somewhere that is falsely indicating extra coil firing events.  I have no idea where you should look, but the back side of the tach or one of the large fairing connectors are prime candidates.

DavidR.

[thkfast]

Gotcha! 

I'll chase that grey wire as far as possible.  Now, when it comes to "cleaning" the connectors, do you mean
unplug them and swirl a Q-tip dipped in alcohol around up in there?  I appreciate your suggestions!

[SlowOldGuy]

Gotcha! 

I'll chase that grey wire as far as possible.  Now, when it comes to "cleaning" the connectors, do you mean
unplug them and swirl a Q-tip dipped in alcohol around up in there?  I appreciate your suggestions!

Or scrape any green corrosion off of them.  They tend to get a fair amount of water on them if you ride in the rain or wash the bike frequently, which can lead to corrosion.  It's a good idea to periodically inspect/clean/lube any/all connectors you can get your hands on.  Even removing the fairing to get to the other hard to reach connectors is a adviseable.

Years ago, Norbert showed up at a rally on Calvin's bike because his '89 lost fire on 2 cylinders as he was headed through Va.  Once the recalcitrant bike was delivered to the rally on a  trailer, Andy York, himself, tried to find and fix the problem.  Then I took a turn, followed by several other poeple.  We swaped relays and every other black box we could get to.  Nothing was working.  Finally, Andy just started pulling connectors.  Everything he could get his hands on.  Nothing really looked out of order, but when we put everything back together, suddenly the problem was gone!

Moral: A little connector cleaning can sometimes work magic. 

DavidR.

[thkfast]

UPDATE: Talking to my Yamaha Service Advisor, he believes either the tach is going bad (I don't think so) or there's a problem with the CDI.  I think it's buried under the right side fairing...I can't see it.  I'll re-post after I take the bike in.

Hey!  And it's only $629...oh shit.

[SlowOldGuy]

Don't even think about replacing the stock CDI black box.  If it's bad (whcih I seriously doubt) then install a Dyna instead.  Significantly cheaper than the $600!

If the CDI was bad, then the engine would have some kind of trouble running.  The tach wire is spliced into a coil ground wire and the tach just counts the on/off voltage transitions.  Maybe a problem with the tach, but the CDI should be fine.

DavidR.

[thkfast]

Okay.  Yeah bike runs perfectly.  I'm slowly pulling stuff apart to get behind the fairing to physically get at all the wires going to the tach.  Unplugging and plugging back in anything and everything I can get my hands on!  The thought of pulling the entire fairing off sucks.  Thanks again.