XS1100 Standard Fuel Gauge Component Failures and Adjustments

[3Phase]

Since I apparently cannot remember anything once I see something shiny
I took some pictures of the XS1100 Standard fuel gauge components and
labeled everything.

for information and troubleshooting, the flow of current in the circuit is:

A Brown wire carries 12 volt system voltage from the 20 amp Signal fuse
up to the 7 volt regulator in the tachometer housing.

The 7 volt regulator connects to the fuel gauge Positive terminal with a Red/Black wire.

Current flows through a precision resistor wire wrapped around a bi-metallic arm
in the fuel gauge, then continues out from the Negative terminal on the Green
wire that runs down to the 2-pole connector for the in-tank fuel level sending
unit.

The in-tank fuel level sending unit is grounded at the tank and through
the Black wire in the 2-pole connector.

The fuel gauge and the in-tank fuel level sending unit are both fully adjustable.




XS1100 Standard Tachometer and Fuel Gauge Wiring Inside Tachometer Housing





Broken XS1100 Standard Fuel Gauge

















XS1100 In-tank fuel level sending unit





XS1100 In-tank fuel level sending unit with broken resistor wire

[motoman]

clear pics and notations make that simple indeed!..............3Phase, got's w-a-y to much free time........but utilizes it well......

[3Phase]

Nah, not that much time, Motoman and it was fun.

It took about an hour and a half off and on as I was working on the '79. Most of the time was just playing around with the Paint.NET image editor while I tried to figured out what it can do, then how to ignore all of the fancy stuff and do something simple like add color text and shapes to pictures.

[skids]

You must have a box-full-of-tachometers like me. For those who might be considering buying one from ebay, the fuel gage should read zero in any piture. You should ask the seller to chek for needle deflection when tipping the tach from side to side. This is not a for sure test, but it can weed-out some of the junk ones.

[3Phase]

Yep, you got it, Skids, I have a bunch of the darned things along with several speedometers.

All of the spare tachometers have bad fuel gauges that broke just beyond the anchor for the bi-metallic arm. That is the weakest link and it fails after only thirty years of on/off/run cycles and bouncing down the road.

Unfortunately, all of the spare tachometers and speedometers that I have are for Standards, nothing for Specials but with a little work most of the parts will interchange.

I rebuilt the speedometer and tachometer for the '79 Special by cannibalizing parts from two Standard speedometers and one Standard tachometer so I was able to make one good set of unbroken and unmelted gears and numbers for the speedometer. The Special's tachometer had a broken end-spring in its galvanometer because the P.O. cut open the housing with a hacksaw. The metal filings went straight for the magnet in the galvanometer where they slowly gnawed through the upper return spring and almost through the lower return spring. A spare tachometer with an intermittent armature winding cheerfully donated both of its end-springs to the cause.

[bikerphil]

Back about 20 yrs. ago I repaired the bi-metal on a 79F fuel guage by soldering it and it worked fine. It still works to this day but is no longer on the bike. It did take just slightly longer to register the level than normal but was still accurate as it should be. IIRC, it was a very delicate procedure soldering it back together but it can be repaired if needed.

[3Phase]

Phil, you're a genius!

A solder repair was next on the agenda because I'm down to my last working fuel gauge but I didn't know if it would work.

I cut a small strip from a scrap piece of brass shim stock and tinned all the parts with solder, then just held the brass in place with the tip of the soldering iron and watched it settle itself in place. A quick test with a 9V battery shows that the gauge works, it just needs to be calibrated.

Thank you!


As always, just click on the image to see the larger version:-

[bikerphil]

Awesome, nice repair. Ought to be good for another 30 yrs.

[3Phase]

Thanks, Phil, that's a b-fugly gauge I used to test your repair. Now that I know it works I'll fix up a pretty one for a spare.

[cywelchjr]

Awsome. My gauge works just fine, but the needle looks like crap. I'm not sure how hard it is to get it out of there to try and dress up the needle and make it look nice again though. I sure don't want to open the tach face to do it if that's required, I'll live with it in that case. But the end has kind of split a little bit, so it would be nice to be able to go in there and fix that up a little very very carefully, that and check that stress point and maybe repair it BEFORE it breaks if it looks like it might be getting ready to break.

BTW, for this interested, that regulator is nothing more than a 7807 regulator or equivalent and can be gotten from places like digikey for under $5 shipped.

[3Phase]

Cy, you do have to remove the front bezel to take out the gauge or to paint the needle.

I'm not sure what kind of paint it would take but no hacksaw....


I do have to say something about general purpose IC regulators for anyone that wants to live a long or at least a happy life beyond that first twist of the ignition switch after installing a home-brew voltage regulator:

General purpose IC regulators are not -- NOT! designed to supply anything what-so-ever to anything that is even in the general vicinity of a tank of gasoline laced with conductive, waterlogged ethanol.

I reverse-engineered the Yamaha 7V regulator and, yes, I used a LM317T to roll my own for the fuel gauge circuit in Columbo. I also added several discrete components to help it survive and to ensure that when it does fail it will fail safely.

That regulator has worked flawlessly for three years and I have not been covered in burning gasoline but I hope you understand why there is no schematic.

[cywelchjr]

Originally Posted by 3Phase

Cy, you do have to remove the front bezel to take out the gauge or to paint the needle.

I'm not sure what kind of paint it would take but no hacksaw....


I do have to say something about general purpose IC regulators for anyone that wants to live a long or at least a happy life beyond that first twist of the ignition switch after installing a home-brew voltage regulator:

General purpose IC regulators are not -- NOT! designed to supply anything what-so-ever to anything that is even in the general vicinity of a tank of gasoline laced with conductive, waterlogged ethanol.

I reverse-engineered the Yamaha 7V regulator and, yes, I used a LM317T to roll my own for the fuel gauge circuit in Columbo. I also added several discrete components to help it survive and to ensure that when it does fail it will fail safely.

That regulator has worked flawlessly for three years and I have not been covered in burning gasoline but I hope you understand why there is no schematic.

That's interesting, cause my OEM regulator initially failed HIGH, providing full 12 volts to the gauge, luckily not burning it out or otherwise, so I'm not feeling like that part is such a failsafe part (most of the automotive ones I've had fail failed high, not low). I think you attribute FAR too much safety engineering to Yamaha in those parts. Most of them were built as cheap as they could and figure they would last as long as they thought they needed to. No redundant clamping parts to force an internal fuse to blow when they short internally and provide full input voltage on the output. I frankly trust a modern single piece voltage regulator more as long as you make sure its not the proper protection (or spend the extra 2 or 3 times as much for the better parts that include that protection inside the part, they are still less than $5 each in single quantities if you stay away from places like Radio Shack). I'll bet that inside that Yamaha regulator is basically a 317T (if not that exact part) as Honda uses a 7807 in their 7 volt regulator for their gas gauge on their CM500's, then incase it in the same stuff that Yamaha does, which makes it overheat . I'm gonna chip mine open and find out just what Yamaha really had in there. The part I used will burn itself out if it tries to exceed 9 volts, it's why I chose it, otherwise I would have added the parts to do that externally.

[3Phase]

Bummer! Almost all of the electrical parts on Columbo so far except for the TCI have failed 'high' or 'short' for me, too!

I really did not want that to happen again so I built a better mousetrap and put a guy next to it with a crowbar; large floppy hat, hood, belt, suspenders, thermal underwear, waterproof jacket, hip waders, heated socks, a pack of smokes and a Zippo lighter to keep an eye on the cheese.

Since the water and alcohol content in our fuel has gone steadily upward and there has not been a sudden rash of fuel gauges burning up bikes, most of the stock 7V regulators still okay.

When these bikes were designed ethanol was nothing but a distant nightmare that would be handled in the future by 'someone else'. Gasoline that used to be pretty much non-conductive now grabs water if you sneeze near it and it is definitely conductive. The old design used to be good enough but now, to quote Porgy and Bess, "It ain't necessarily so!"


In the regulator I took out of my bike I found: a power transistor in a TO-220 package; RC network; smaller transistor in a TO-92 package; a small shorted and burned diode. I could use an oscilloscope to confirm how I think the regulator worked but I don't have one and I'd just be guessing.

So, no, I don't really attribute much of anything to Yamaha's regulator design except that the one in my bike worked until it didn't and I didn't die when it failed.

[cywelchjr]

Originally Posted by 3Phase

Bummer! Almost all of the electrical parts on Columbo so far except for the TCI have failed 'high' or 'short' for me, too!

I really did not want that to happen again so I built a better mousetrap and put a guy next to it with a crowbar; large floppy hat, hood, belt, suspenders, thermal underwear, waterproof jacket, hip waders, heated socks, a pack of smokes and a Zippo lighter to keep an eye on the cheese.

Since the water and alcohol content in our fuel has gone steadily upward and there has not been a sudden rash of fuel gauges burning up bikes, most of the stock 7V regulators still okay.

When these bikes were designed ethanol was nothing but a distant nightmare that would be handled in the future by 'someone else'. Gasoline that used to be pretty much non-conductive now grabs water if you sneeze near it and it is definitely conductive. The old design used to be good enough but now, to quote Porgy and Bess, "It ain't necessarily so!"


In the regulator I took out of my bike I found: a power transistor in a TO-220 package; RC network; smaller transistor in a TO-92 package; a small shorted and burned diode. I could use an oscilloscope to confirm how I think the regulator worked but I don't have one and I'd just be guessing.

So, no, I don't really attribute much of anything to Yamaha's regulator design except that the one in my bike worked until it didn't and I didn't die when it failed.

Actually I used to run Gasohol in my car in high school in the 70's. It wasn't everywhere though, and it was an extra cost option and was sold as giving you extra performance by raising the octane of the gas. I forget the percentage that was used back then, but you actually had to go looking for it. If I had known then what I know now, I would have stayed as far away from that stuff as I could, but we believed what we were told back then.

[3Phase]

Originally Posted by cywelchjr

Actually I used to run Gasohol in my car in high school in the 70's. It wasn't everywhere though, and it was an extra cost option and was sold as giving you extra performance by raising the octane of the gas. I forget the percentage that was used back then, but you actually had to go looking for it. If I had known then what I know now, I would have stayed as far away from that stuff as I could, but we believed what we were told back then.

Yes, and most of those were service stations, not self-service stations. A guy came out to put gas in the tank, clean the windows, check the oil and the tires and tried to up-sell me because some dragsters and funny cars used alcohol. Aside from being different alcohols I wasn't really interested in burning through ~20 gallons in a 1/4-mile or popping wheelies in my Corvair anyway so I just smiled and told him to fill it with Regular.