The Tach and its secrets.....

[DGXSER]

ok....so some are still pretty much secrets to me. The tach on SG never worked correctly. I swapped tachs with my SH and the tachs acted the same on the other bike, the same tach malfunctioned the same way on the SH as it did non the SG. So, I tore the tach down to see if I could discover its secrets and what it needed to perform properly. Well...I am not as talented at electronics as some folks are. But I did get my tach torn down pretty far, so I thought I would share with the class the wondrous things I found inside there.

Here is the photos I took to make sure I knew which light to put back in which hole...







After all the lights and wiring harness are removed.



Here is the trim ring in the process of peeling it back to remove it.


With the trim and case removed...


Side view of the internal componenets


The other side


After removing the needle and face plate....


It appears the electronics controls how much magnetic field is created to move the "motor" the needle is mounted to. That shaft has small springs, like a mechanical watch hairspring, on each end to wind it back to zero when the power drops off form the motor magnet.

I fo not know how to tell which of those electronic components are functioning or malfunctioning. I am pretty sure it takes more complicated equipment than I have to figure that out.

[sparkfly88]

Still pretty cool regardless if you can fix it or not.

[jayel]

what problem were you having with the tach? a jumpy erratic tach may just be a poor ground and/or poor connection on the feed wire from the alt., mine jumped about a thousand rpm at steady cruise, ran a extra ground from the reg/rec to battery frame ground and no more jump

[DGXSER]

The tach operation is very eratic. It tends to just sit at 3500 RPM, but then if I tach it up it jumps up some, but is bouncy. Let off the throttle and it drops to maybe 1000, but then jumps back to 3500.

I have two XS11s, an 81 and an 80. This tach was on the 80. I moved the tach from my 81 (SH) over to the 80 (SG) and it worked perfectly. I also put this tach on my SH and it worked just as imperfectly. Since I am selling the SG, I left the good tach on there.

I would try to fix this one if I knew anything about those electronics. I know the colored rings tell you the capacity of some of the components, but I have no idea how to test them. I knew I should have paid better attention in Circuits class almost 30 years ago.

[jetmechmarty]

Bad Boys Rape Our Young Girls, But Violet Gives Willingly.

[edgo]

My tach was jumpy so I took the cover off, sprayed some WD40 into one of the holes and its been fine since then. That was five years ago.

[jayel]

My tach was jumpy so I took the cover off, sprayed some WD40 into one of the holes and its been fine since then. That was five years ago.

I hate WD-40, it is Water Dispercent formula 40 it is Not a lubricant it Not a cleaner, it works well for its intended purpose but most people don't use it correctly (end rant) if it worked, fine but spraying anything into a tach or speedometer usually has more consequences than benefits

[natemoen]

Plus wd-40 has a strong tendancy to dry up and get really gummy and sticky....

[edgo]

The WD40 can says it "lubricates, protects, penetrates and displaces water". My tach probably needed all four of these intended purposes.

[TopCatGr58]

Hey DGXser,

I, too, am not an electronics wizard, however, I was able to resurrect a couple of old professional grade VCR's I had by replacing ALL of the capacitors in the power supply. The little pieces with wires sticking out of both ends with colored bands are RESISTORS, and they usually don't fail so easily. But the large cylindrical pieces are liquid filled electrolytic capacitors, and they are known to Dry UP, etc.! I found capacitors on ebay relatively cheaply....radio shack usually doesn't carry very many sizes or power ranges.

The gray one in your picture is a 16 volt, and 47 microfarad(uf) one, and they have POLARITY...+ and - side marked with same on side of capacitor. I can't see the smaller black one. Make a diagram of the polarity before removing them. I would suggest desoldering those, and getting replacements and soldering them back in, and then test your tach before fully assembling it. I would bet money that replacing those capacitors would probably fix the problem.

T.C.

PS, post the value of the smaller one in a reply, and I'll check my small stash of capacitors, if I've got the right sizes, I'll be happy to send you them in the mail.

[DGXSER]

Hey TC, thanks for the advice and offer!!
As it turns out, I did some internet searches today and had identified the capacitors and resistors. I found how to test capacitors and resistors, and diodes. So I got a little braver in my dis assembly of the device, and well......one of those hairsprings is now a wire...straight that is. So, the thing is pretty well toast.

Fortunately, I have a few options I am investigating for a replacement tach. The good news is the replacement does not need a nice clean chrome case, I have one of those. Just work correctly.

[DiverRay]

Looking at the pictures, you have the Blue, and black electrolytic, a blue tantilum, and the red, flat cap. I do think the ground, plus the two electrolytic caps, are the most of the problems with the tachs.
This is just my guess, as I have yet to take the tach off the MNS to fix it.

[WMarshy]

Any plans to go through and check the electrolytic capacitors?

[DAVINCI]

Bad Boys Rape Our Young Girls, But Violet Gives Willingly.

HA HA Marty! i learned the color code the same way!!

[DAVINCI]

Any plans to go through and check the electrolytic capacitors?

That would be my route, just replace the caps There's nothing else in there that's going to go stale. Except possibly the solder joints can get corroded.