[Dr. Zo]

Headlight.
You don’t mention whether the headlight Hi/Lo switch is working or not.

Fork drain screws.
These are not Phillips heads they are Posidrive, a Phillips bit will “cam out” and ruin the screw.
Use the correct PZ bit, give it a sharp tap with a hammer, straight on, before attempting to loosen and they will come undone. I use a little 1/4” drive socket set with a hex bit adapter for jobs like this, works great.

Newsh, thanks for the info on the driver type. I found that I had some of the Posidrive bits and one of them worked perfectly after following your advice to give it a tap with a hammer first. The screws came out easily and the forks have new oil now. I'm sure in the past I have bunged up some posidrive heads without realizing they were a different type than Phillips. I'll be more aware now - thanks.

On the headlamp I guess I wasn't too clear. I tested things a bit more and here is what I found: The 3 position toggle lighting switch - when it is off (left) nothing comes on, good. When in the middle position the parking lights come on, good. In the position full to the right, when the headlamp is supposed to come on it does not. If I jiggle the Dipper switch for the headlights, I can get both low and high beams to come on, it just doesn't occur at the up or down detent - they come on somewhere in-between. Also, the headlight flasher button works, when depressed the high beam comes on.

So I believe the problem lies in the dipper switch, perhaps it is worn or something. I'll probably be taking this apart to take a look. It seems the wiring is ok, it is the dipper switch mechanism that is the problem.

 

[newsh]

Hi
Excellent news on the fork drain screws!

Below is a comparison picture showing the difference between Phillips and Pozi. At work I used to send pictures like this out to customers along with Pozi bits and bags of 100 replacement screws!

Yes it certainly seems like it’s the contacts in the Hi/Lo dipper switch, which is what I suspected.
It should respond to some careful dismantling and cleaning. You might find a loose connection that needs soldering.
Advice I’ve read on here is to disassemble the switch inside a large clear plastic bag to capture any small springs and ball bearings that have a tendency to launch themselves into the furthest corner of the workshop/kitchen.

 

[StuartMac]

Hi,

headlamp
3 position toggle lighting switch - when it is off (left) nothing comes on, good. When in the middle position the parking lights come on, good. In the position full to the right, when the headlamp is supposed to come on it does not. If I jiggle the Dipper switch for the headlights, I can get both low and high beams to come on, it just doesn't occur at the up or down detent - they come on somewhere in-between.

The wiring diagram for your bike is in the Triumph 350/500 workshop manual - Section HH (supplement at the end of Section H), page HH6. If you don't have a paper manual, http://www.classicbike.biz/Triumph/Repair/350-500/63-74-350-500cc-Repair.pdf and page 248.

The diagram shows the handlebar dipper switch (at the bottom of the diagram) is fed by a plain Blue ("U") wire from the toggle lighting switch. However, be aware there's a misprint on the diagram - it shows the Blue wire connected to toggle switch terminal #6; in reality, the wire is/should be connected to terminal #8.

From the dipper switch, the Blue/White wire goes to the headlamp bulb high beam filament, the Blue/Red wire goes to the headlamp bulb low beam filament.

When dismantling the handlebar switch cluster, ideally detach it completely from the bike and lay it outer face down on a towel (the switch cluster contains small balls and springs, the towel will stop them rolling far if they fall out of the switch cluster).

Switch cluster held outer face downwards, joint face horizontal, undo the cluster internal screws roughly equally and, when all are released and withdrawn, lift the top part of the switches away slowly and carefully; with a bit of luck and a following wind, all the balls and springs should stay in place in the lower part of the switches. If you can, take a few photos. of the positions of balls and springs before you lift them out carefully ... because you can't put the switch cluster down 'til you do.

Advice I’ve read on here is to disassemble the switch inside a large clear plastic bag to capture any small springs and ball bearings that have a tendency to launch themselves

More of a problem on the later '75-/'76-on 182SA and 187SA switch clusters. While I wouldn't dissuade you from dismantling/assembling inside said bag, as I say, if you loosen your bike's switch cluster screws equally, the springs tension is relieved before the switches come apart fully.

If I jiggle the Dipper switch for the headlights, I can get both low and high beams to come on, it just doesn't occur at the up or down detent - they come on somewhere in-between
worn or something

Ime, more likely is the spring and/or ball to locate the switch lever in its up or down position is missing (courtesy of DPO?). Whatever you find, luckily a parts kit is available for this particular Lucas switch cluster type - "lucas 169SA repair kit" into your preferred internet search engine.

headlight flasher button

Independent of the switches and wiring above - while the button also has a Blue/White wire to where it and the Blue/White from the dipper switch both connect to the Blue/White in the main harness (under the tank?), the button is supplied by a White wire, that's 'hot' any time the ignition switch is on.

Hth.

Regards,

 

[Dr. Zo]

Hi,

The wiring diagram for your bike is in the Triumph 350/500 workshop manual - Section HH (supplement at the end of Section H), page HH6. If you don't have a paper manual, http://www.classicbike.biz/Triumph/Repair/350-500/63-74-350-500cc-Repair.pdf and page 248.

The diagram shows the handlebar dipper switch (at the bottom of the diagram) is fed by a plain Blue ("U") wire from the toggle lighting switch. However, be aware there's a misprint on the diagram - it shows the Blue wire connected to toggle switch terminal #6; in reality, the wire is/should be connected to terminal #8.

From the dipper switch, the Blue/White wire goes to the headlamp bulb high beam filament, the Blue/Red wire goes to the headlamp bulb low beam filament.

When dismantling the handlebar switch cluster, ideally detach it completely from the bike and lay it outer face down on a towel (the switch cluster contains small balls and springs, the towel will stop them rolling far if they fall out of the switch cluster).

Switch cluster held outer face downwards, joint face horizontal, undo the cluster internal screws roughly equally and, when all are released and withdrawn, lift the top part of the switches away slowly and carefully; with a bit of luck and a following wind, all the balls and springs should stay in place in the lower part of the switches. If you can, take a few photos. of the positions of balls and springs before you lift them out carefully ... because you can't put the switch cluster down 'til you do.


More of a problem on the later '75-/'76-on 182SA and 187SA switch clusters. While I wouldn't dissuade you from dismantling/assembling inside said bag, as I say, if you loosen your bike's switch cluster screws equally, the springs tension is relieved before the switches come apart fully.


Ime, more likely is the spring and/or ball to locate the switch lever in its up or down position is missing (courtesy of DPO?). Whatever you find, luckily a parts kit is available for this particular Lucas switch cluster type - "lucas 169SA repair kit" into your preferred internet search engine.


Independent of the switches and wiring above - while the button also has a Blue/White wire to where it and the Blue/White from the dipper switch both connect to the Blue/White in the main harness (under the tank?), the button is supplied by a White wire, that's 'hot' any time the ignition switch is on.

Hth.

Regards,

OK, I guess it's time to take this off and learn something new again. Thanks!

 

[Dr. Zo]

I am rebuilding the carburetor on this bike as I believe that was the problem I was having with intermittent fueling. It turns out the float was worn through so was likely sticking. I've got the carb apart and waiting for parts.

I decided to redo the fuel lines also and when examining found that the petcocks were leaking, that is when fully closed there was still some fuel coming through.

I was hoping I could rebuild the petcocks also, as there seems to be a rubber washer inside the petcock that could be replaced. I haven't found anything on-line about rebuilding these so I am wondering if any of you have rebuilt your petcocks previously, and if so where did you find the new internal pieces?

Thanks for your help!

 

[Dr. Zo]

So I never found a rebuild kit for my peacocks. I went to ace hardware and found some o rings the same size as in these old petcocks - as the old ones were hard as a rock. It was relatively easy to disassemble the petcocks, clean them with 000 steel wool, replace the o ring and put back together. Now to test them for leaks.

 

[Dr. Zo]

So, I made sure the vent on my petrol tank was clear and went for a ride. After about 15 minutes of riding I thought the problem, of cutting out at lower rpms, was solved so continued to ride. Then after another 5 minutes of riding it started to cut out again when the rpms got low, like when I stopped for a light it started to cut out and I had to give is some throttle to keep running. This also happened if I went to a higher gear and was sort of lugging the engine - it would start to cut out altogether so I had to downshift to keep the gas on and revs up. Any other ideas are appreciated on how to diagnose this.

One more thing. I went to replace the headlight bulb as it was burned out. I put the new bulb in and it would only light up when I had the switch fully on and pressed the high beam. So the parking light works as it should, the horn works as it should, but the headlamp only comes on when the lamp switch is fully on (to the right) and I press the high beam button. Any advice on how to trouble-shoot this before I start taking things apart?

Lastly, I was going to replace the fork oil. However I found that the fork drain plugs were fixed with a phillips screw head bolt. On my other bike I have a regular hex head bolt. These don't seem to want to come out easily and I wanted to see if anyone had any experience with this before I try to remove them? I may have to use an impact driver.

Thanks.

So, I rebuilt the carb and installed it tonight, hoping it would solve the problem of cutting out. It started right up after 2 kicks and smoked a bit, probably due to not having been run for awhile. The the problem started again. It would start up, sometimes run smooth, sometimes rough. If I got it running and held the throttle at one position, the revs would not stay stable but run higher and lower. Then it would start to cut out and I could keep it running if I manipulated the throttle up and down, but eventually it stops. It seems like it is getting starved of fuel, but I am not sure because it would start up and run a bit. Then there were times if I gave it too much throttle it would die. So I am not sure what to check next and welcome any thoughts. Ran it with the gas cap in and off and no difference. Thanks for any advice!

 

[StuartMac]

Hi,

Consider electrical - the described symptoms are also of a poor electrical contact that heats up when conducting 'til it fails, cools after it stops working, works again once it's cooled.

Your original post says the bike has a Boyer-Bransden EI, please post which one. Nevertheless, an obvious test would be to connect a Voltmeter across the battery and see what the reading is:-

. before anything's turned on,

. after just the ignition is turned on.

If both of these meter readings are at least 12.5~12.6 Volts, with the ignition turned on, use the meter to measure between the battery +ve terminal and where the B-B Transistor Box White wire is connected to a bike White/Yellow wire (don't disconnect the wires, just expose the metal terminals for the measurement then cover them up again), post the difference between this latter meter reading and the "after just the ignition is turned on" meter reading.

Meter connected across the battery again, start the bike and watch the meter reading, note what the meter displays if/when the engine starts to run rough.

Hth.

Regards,

 

[Dr. Zo]

Hi,

Consider electrical - the described symptoms are also of a poor electrical contact that heats up when conducting 'til it fails, cools after it stops working, works again once it's cooled.

Your original post says the bike has a Boyer-Bransden EI, please post which one. Nevertheless, an obvious test would be to connect a Voltmeter across the battery and see what the reading is:-

. before anything's turned on,

. after just the ignition is turned on.

If both of these meter readings are at least 12.5~12.6 Volts, with the ignition turned on, use the meter to measure between the battery +ve terminal and where the B-B Transistor Box White wire is connected to a bike White/Yellow wire (don't disconnect the wires, just expose the metal terminals for the measurement then cover them up again), post the difference between this latter meter reading and the "after just the ignition is turned on" meter reading.

Meter connected across the battery again, start the bike and watch the meter reading, note what the meter displays if/when the engine starts to run rough.

Hth.

Regards,

Stuart, thank you. It is a BB MICRO-MKIV, for Triumph/BSA Twin, KTT00052, 12 Volt. I will go through this procedure you described and see what I find out.

 

[StuartMac]

Hi,

is a BB MICRO-MKIV

Bransden reckons these aren't so sensitive to low Volts as the Mk.III could be. Nevertheless, I'm a firm believer that, as they're "12V", that's the absolute minimum they and connected coils should have across 'em, lower than 12V is an electrical fault that simply needs fixing.

Assuming the bike's electrics are standard 'positive ground', other things I check/remedy on any EI as a matter of course:-

. "Transistor Box" Red wire connected directly to the battery +ve terminal, not anywhere else on the bike (e.g. "POSITIVE FRAME GROUND" on the B-B wiring diagram );

. similarly, wire from coils array +ve terminal connected either directly to the battery +ve terminal or at least into the bike's existing harness Red wires (again, not "POSITIVE FRAME GROUND");

. harness Red wire connected to an engine component - e.g. one of the head-steady bolts/studs through a rocker-box under the tank.

Hth.

Regards,

 

[Dr. Zo]

Hi,

Bransden reckons these aren't so sensitive to low Volts as the Mk.III could be. Nevertheless, I'm a firm believer that, as they're "12V", that's the absolute minimum they and connected coils should have across 'em, lower than 12V is an electrical fault that simply needs fixing.

Assuming the bike's electrics are standard 'positive ground', other things I check/remedy on any EI as a matter of course:-

. "Transistor Box" Red wire connected directly to the battery +ve terminal, not anywhere else on the bike (e.g. "POSITIVE FRAME GROUND" on the B-B wiring diagram );

. similarly, wire from coils array +ve terminal connected either directly to the battery +ve terminal or at least into the bike's existing harness Red wires (again, not "POSITIVE FRAME GROUND");

. harness Red wire connected to an engine component - e.g. one of the head-steady bolts/studs through a rocker-box under the tank.

Hth.

Regards,

Thanks again Stuart. I now have a good trouble-shooting list to guide me. As a matter of course, if it is an electrical problem, is the case that something like a transitory short is starving the coils off and on - thereby making one or both sparks to fail? I'm still trying to understand these electrical systems.

 

[StuartMac]

Hi,

if it is an electrical problem, is the case that something like a transitory short is starving the coils off and on - thereby making one or both sparks to fail?

Strictly-speaking, a "short" is a short-circuit; in this case, very unlikely.

However, if you mean a short-term break in one or more of the ignition circuit components and/or connections, that then breaks the ignition circuit, more likely.

I'm still trying to understand these electrical systems.

One thing to know is:-

. Any EI for Brit twins, multiple ignition coils are (should be) connected 'in series' - i.e. in this case:-

.. the B-B Transistor Box Black wire (the switched wire) is connected to only one coil "-" terminal;

.. that coil's "+" terminal is connected to the second coil's "-" terminal;

.. only the second coil's "+" terminal is connected to either the battery +ve terminal or the bike's existing harness Red wires;

.. because multiple ignition coils are connected in series, a problem with one coil's LT stops both coils generating HT sparks, only each cylinder's HT components (coil, HT lead, plug cap, spark plug) work independently of the other cylinder's.

If the problem is electrical, the tests I've suggested so far should start to narrow-down where the problem might be; however, either finally finding the problem or eliminating all possibilities can be a tedious process.

Hth.

Regards,

 

[Dr. Zo]

Hi,

Strictly-speaking, a "short" is a short-circuit; in this case, very unlikely.

However, if you mean a short-term break in one or more of the ignition circuit components and/or connections, that then breaks the ignition circuit, more likely.


One thing to know is:-

. Any EI for Brit twins, multiple ignition coils are (should be) connected 'in series' - i.e. in this case:-

.. the B-B Transistor Box Black wire (the switched wire) is connected to only one coil "-" terminal;

.. that coil's "+" terminal is connected to the second coil's "-" terminal;

.. only the second coil's "+" terminal is connected to either the battery +ve terminal or the bike's existing harness Red wires;

.. because multiple ignition coils are connected in series, a problem with one coil's LT stops both coils generating HT sparks, only each cylinder's HT components (coil, HT lead, plug cap, spark plug) work independently of the other cylinder's.

If the problem is electrical, the tests I've suggested so far should start to narrow-down where the problem might be; however, either finally finding the problem or eliminating all possibilities can be a tedious process.

Hth.

Regards,

Well, guess I will have to be patient with tedious. Thanks for being complete in your instructions!

 

[Dr. Zo]

So Stuart, I started to trouble shoot this and determined I may need a longer time than a couple of hours to diagnose this.

I used a voltmeter to check the battery before anything was turned on: 12.21

After the ignition is turned on: 12.08

Obviously I haven't ridden the bike much lately and it is not on a trickle charger.

I was trying to find where the B-B Transistor box White Wire is connected to a bike White/Yellow wire, but they are pretty well covered and it looks like I will have to remove the gas tank to find this connection. So when I get a block of time where I can do this I will.

A couple of other things, however. I can get the bike to start, and now it never runs nicely, always rough and variable. A bit of smoke too. While it was running I disconnected the left spark plug wire and it kept running at about the same pace. So I reconnected the wire and again, while it was still running, I disconnected the right spark plug wire and it kept running, roughly of course, but similar to when I disconnected the left plug. Might this be diagnostic of anything specific? Thanks!

 

[StuartMac]

Hi,

started to trouble shoot this and determined I may need a longer time than a couple of hours to diagnose this.

I used a voltmeter to check the battery before anything was turned on: 12.21

After the ignition is turned on: 12.08

Obviously I haven't ridden the bike much lately and it is not on a trickle charger.

I was trying to find where the B-B Transistor box White Wire is connected to a bike White/Yellow wire, but they are pretty well covered and it looks like I will have to remove the gas tank to find this connection. So when I get a block of time where I can do this I will.

'Til you get time to work longer on this, whip out the battery and connect it to a low-Ah (1/10th battery Ah) trickle-charger at least overnight? This'll determine whether the battery can be charged or has turned up its toes.

can get the bike to start, and now it never runs nicely, always rough and variable. A bit of smoke too. While it was running I disconnected the left spark plug wire and it kept running at about the same pace. So I reconnected the wire and again, while it was still running, I disconnected the right spark plug wire and it kept running, roughly of course, but similar to when I disconnected the left plug. Might this be diagnostic of anything specific?

I'd suggest generally - both plugs are likely misfiring intermittently(?), might be an electrical problem affecting the EI, which'd affect both plugs, might be a fuelling problem, single carb. will affect both cylinders ...

Ain't old bikes fun ...

Hth.

Regards,

 

[Dr. Zo]

Hi,

'Til you get time to work longer on this, whip out the battery and connect it to a low-Ah (1/10th battery Ah) trickle-charger at least overnight? This'll determine whether the battery can be charged or has turned up its toes.


I'd suggest generally - both plugs are likely misfiring intermittently(?), might be an electrical problem affecting the EI, which'd affect both plugs, might be a fuelling problem, single carb. will affect both cylinders ...

Ain't old bikes fun ...

Hth.

Regards,

Seems like fun - at least keeps one's mind busy - good for the brain too I believe!

 

[Dr. Zo]

Electrical troubleshooting! I'm still having trouble troubleshooting my 1971, Triumph, T100C electrical issue. I checked the wiring of the Boyer-Brandsen MK IV and it looks to be properly appointed. As far as I can see it is getting juice. I made a YouTube video in case any members can take a look and help me a bit more with the diagnosis. Thanks if you'll take a look here:

 

[Dr. Zo]

Electrical troubleshooting! I'm still having trouble troubleshooting my 1971, Triumph, T100C electrical issue. I checked the wiring of the Boyer-Brandsen MK IV and it looks to be properly appointed. As far as I can see it is getting juice. I made a YouTube video in case any members can take a look and help me a bit more with the diagnosis. Thanks if you'll take a look here:

Now I am wondering if this is a different electrical problem or a carb problem. See the attached video of the plugs sparking when kicking the engine over. They seem consistent and uniform. Also, the plugs are wet when removing after running, so could this be a fueling issue and how would I troubleshoot this?

https://youtube.com/shorts/C3Ui9Z6fVgQ?

 

[Dr. Zo]

I'm still trying to figure this out. So the bike starts easily, but still runs rough, like it is missing intermittently. When running I removed one the right spark plug wire and it kept running, but less firing. After connecting the right plug, I then removed the left, and it kept running, but just barely. So it would seem the left side is not running as smoothly as the right side. So could this be a left side coil or wiring issue that for some reason is not letting the left side spark as strongly as the right side? Thanks for advice!

 

[Dr. Zo]

OK, so I tried switching coils. I ran the bike with the spark plugs wires switched to the other plugs - ran the same rough. Then I started and ran the bike on the right cylinder only, once with the left coil and once with the right coil. I did the same with the left cylinder. All four times it seemed to run the same, no missing just running on once cylinder. So I am wondering what this tells me . . . it seems that both coils are working OK? Also both spark plug wires seem to work ok, even on just one cylinder. So when I hook the plugs up normally, it is still running rough, so more than one cylinder is firing, just not evenly. Any advice?