Potential new project

[James England]

Fuel gauge help please!

I'd like to get the fuel gauge working. It isn't but I'm not sure why, so may I run this by everyone please?.....

The sender unit shows varying resistance through the two wires from it, as the float is moved up and down. The distance reading varies smoothly and progressively as the float arm is moved up and down..so that's working as it should, right?

However, when connected to the wiring loom, absolutely nothing happens at the fuel gauge.

Similarly, nothing happens at the fuel gauge if I join the two wires at the block on the loom. The gauge needle is absolutely motionless.

So, is it likely to be the fuel gauge regulator thing in the tacho casing, do you think? A small black box in there. Is there any way known to the mighty intellect of the forum on how to test this regulator?

Any help would be appreciated!

[donebysunday]

Hi James,

I don't get my standards for about a week but if either has them they are yours. Did not need to look before so I don't know but seem to remember seeing them on one of the bikes.
May stop by and pick up extra parts sooner, if so I'll see then and grab them for you.

[skids]

I'd like to get the fuel gauge working. It isn't but I'm not sure why, so may I run this by everyone please?.....

The sender unit shows varying resistance through the two wires from it, as the float is moved up and down. The distance reading varies smoothly and progressively as the float arm is moved up and down..so that's working as it should, right?

However, when connected to the wiring loom, absolutely nothing happens at the fuel gauge.

Similarly, nothing happens at the fuel gauge if I join the two wires at the block on the loom. The gauge needle is absolutely motionless.

So, is it likely to be the fuel gauge regulator thing in the tacho casing, do you think? A small black box in there. Is there any way known to the mighty intellect of the forum on how to test this regulator?

Any help would be appreciated!

Well, are you getting 7 volts supplied from the gage to the electrical connection under the seat? If not there may be an issues with the volt regulator in the gage housing, or the voltage supplied to that, grounds, or the gage itself is toast. If the needle for the gage is not reading empty when the key is off, the needle is probably broken in the gage. It is a bi-metallic unit that deflects as the current changes from the sender and it can break due to repeated stress.

[James England]

Hi James,

I don't get my standards for about a week but if either has them they are yours. Did not need to look before so I don't know but seem to remember seeing them on one of the bikes.
May stop by and pick up extra parts sooner, if so I'll see then and grab them for you.

Sounds great Done. I'll gladly pay for them but I could send you a couple of bearings for your new bikes, just in case?

[James England]

Well, are you getting 7 volts supplied from the gage to the electrical connection under the seat? If not there may be an issues with the volt regulator in the gage housing, or the voltage supplied to that, grounds, or the gage itself is toast. If the needle for the gage is not reading empty when the key is off, the needle is probably broken in the gage. It is a bi-metallic unit that deflects as the current changes from the sender and it can break due to repeated stress.

right, I'll check the volts at the two-pin block under the seat. Then report back.

The gauge needle IS showing zero when the key is switched off. It permanently stays there......

[James England]

The block under the seat is only showing a reading of 0.20 volts. So that is all the current that's reaching the sender.........

[CaptonZap]

The last bike I did is actually up for sale, I discover yesterday.... http://www.carandclassic.co.uk/car/C440211

Wow! That's over $6000.
Maybe I better start cleaning mine up.
If it sells, you will know what the going rate is for one, and keep your expenditures under that amount.
CZ

[crazy steve]

I'm looking for four of the plastic covers that go on top of the mixture screws on the carbs... They are usually white or yellowish with age and they push on top of the four mixture screws at the front of the carbs, just near the inlet manifolds. Can anyone sell me some please? Or I could do a nice deal on a couple of rear left side wheel bearings as a swap

These will be tough to find as they usually break while removing them. The factory Yamaha carb rebuild kits came with new anti-tamper caps, as did some aftermarket kits 'back when', but these are all long gone unless you can find a NOS kit. You might try checking with some automotive carb restorers/rebuilders as these were pretty common on car carbs in the late 60s/70s, although finding a 'cross' between a car and the bike might be tricky.

[James England]

Wow! That's over $6000.
Maybe I better start cleaning mine up.
If it sells, you will know what the going rate is for one, and keep your expenditures under that amount.
CZ

When I sold the bike three years ago, it sold for $8,349....

[James England]

Well, are you getting 7 volts supplied from the gage to the electrical connection under the seat? If not there may be an issues with the volt regulator in the gage housing, or the voltage supplied to that, grounds, or the gage itself is toast. If the needle for the gage is not reading empty when the key is off, the needle is probably broken in the gage. It is a bi-metallic unit that deflects as the current changes from the sender and it can break due to repeated stress.

There is 0.2v at the block under the seat but 12v going to the voltage regulator. But only 0.2v coming out of it.

I briefly connected a 9v battery to the connections of the gauge itself and it moved up nicely and back down again when I took the battery off.

I think it's the voltage regulator itself...........?

[James England]

Fixed

I bought a NOS voltage regulator wiring harness from the USA and it arrived today, after only a week. Once fitted, the fuel gauge worked immediately. Just to double-check, I put the old one back on and tried again, just in case it was the block connector or fracture wire or something...it didn't work. Then I put the new one on and all worked again immediately. So, result. It's the first time I've encountered that component failing........

[skids]

Glad it worked out for you. I once tried an integrated-circuit VR but it was rated 1/2 volt too high (7.5 volt?) but it was all I could find and I decided to try it anyway. Unfortunately, the reading for the tank was WAY TOO HIGH.

[donebysunday]

Plastic idle mix covers

OK, I was able to come up with only 2 of these caps, on the way to James.
Any chance someone took these off and saved them ?
James only needs 2 more, would be cool

I'm looking for four of the plastic covers that go on top of the mixture screws on the carbs... They are usually white or yellowish with age and they push on top of the four mixture screws at the front of the carbs, just near the inlet manifolds. Can anyone sell me some please? Or I could do a nice deal on a couple of rear left side wheel bearings as a swap

[James England]

OK, I was able to come up with only 2 of these caps, on the way to James.

thanks so much, Done. I really appreciate your kindness

[foreda]

Caps

I may have some caps... I'll go out to the shop and have a look and report back.