Triumphrat

RII · 11-17-2012, 12:40 AM

If it helps, primary thing to remember when working on electrics is open voltage should equal system voltage. Meaning if your battery reads 12.5 volts, you should read 12.5 volts nearly anywhere in your harness. Doesn't matter if it is a bulb socket, coil feed, switch, or otherwise. On newer systems there are exceptions, but for our machines, not so much.

To verify the switch is your issue, you can measure voltage before and after the contact as well. Should be equal. If it is equal, but lower than battery voltage, you have a problem before the switch (wiring, key switch, etc). Not sure on yours, but most of the early handlebar switches were brass. You can break them down and clean with emery cloth and electrical cleaner. Use di-electric grease to help keep them that way after. If you have an issue with carbon or corrosion in the future after using di-electric grease, normally it will just wipe away. You won't have to go through the whole cleaning process again, just wipe off and put a touch more di-electric back on it. I've even rebuilt modern switches this way, as most rocker/push button switches come down to brass contacts internally, no mater how fancy the housing. Just take your time, you'll be fine.

Mr.Pete · 11-17-2012, 02:15 AM

Testing a circuit that has no current load won't tell you much if you're looking at voltage.It would take a massive amount of resistance to show a noticable voltage drop.A resistance test on that circuit or switch would tell you more.

The loaded test that I suggested will show the actual voltage drop when there is a current load on the coils.That's what counts.If the coils don't get 12V then,they don't get enough.

longlimb · 11-17-2012, 04:33 PM

Ok. Did your test Pete. Got about 4 on one coil and almost 10 on the other??

Sent from my iPhone using Motorcycle.com Free App

longlimb · 11-17-2012, 09:19 PM

It's a pretty simple system right? Battery to switch to coils to plugs. If I have a voltage issue it would have to be the switch correct? I took the switch off and it's definitely corroded and dirty. I don't see any copper in there though.

I'm thinking just replace the switch, it's old and could use a replacement. I tried to order one from Dave's suggestion but I haven't heard back from them yet. I emailed them 3 days ago with some questions. Trying to stay away from eBay but might have to risk it.

Sent from my iPhone using Motorcycle.com Free App

RII · 11-18-2012, 12:49 PM

Quote:

Originally Posted by Mr.Pete

Testing a circuit that has no current load won't tell you much if you're looking at voltage.It would take a massive amount of resistance to show a noticable voltage drop.A resistance test on that circuit or switch would tell you more.

The loaded test that I suggested will show the actual voltage drop when there is a current load on the coils.That's what counts.If the coils don't get 12V then,they don't get enough.

With all due respect, we already know that he has a voltage drop. Resisitance through the switch itself should be minimal, hence testing at the leads unloaded. The question becomes is it at the coil, the switch, or somewhere else. You could ceratinly switch to an ohm test and look at resistance in each individual circuit and wire, but not really necessary in this case.

The best test would be testing both primary and secondary windings on each of the coils.

I'm just trying to help avoid replacing parts like the switch unnecesarilly, as it is probably just the coil(s).

Mr.Pete · 11-19-2012, 05:02 PM

Quote:

Originally Posted by longlimb

Ok. Did your test Pete. Got about 4 on one coil and almost 10 on the other??

If you had say 12.5 V at the battery during this test,you should be getting 12V across the 2 coils in series.6V between the terminals of each coil if tested separately.If the primary resistance of both coils is equal,the voltage across each coil should be equal.

longlimb · 11-19-2012, 05:45 PM

Primary resistance on both was 2. And secondary resistance on both got about 5. So coils sounds like they are good.

I need to test the ignition switch. procedures?

RII · 11-22-2012, 12:14 AM

Assuming that 79's remained the same as earlier years, you should have 12v coming into the kill switch on the "white" wire. Should be the same exiting the switch on the "white/yellow" wire headed to the ignition coils. Please note that depending on your switch type, the white wire can be bridged between a couple of the switches, so you will need to check it at all points prior to the kill switch.

I would start with a simple voltage test first for verification. Just in case there is a parasitic draw at a coil, etc, disconnect the "white/yellow" spade from the coil terminal. Make sure you have battery voltage coming from the "white" wire into the kill switch (should be fed by the ignition lock circuit). If you do, great, if not, trace the white wire back towards the lock cylinder, or skip a step and check it straight at the lock cylinder.

Provided you are getting 12volts at the white wire at the switch, check for 12v coming out of the switch on the white/yellow wire. I would cycle the button while you are checking to see if voltage changes. Should go from 12v to 0v and back repeatedly. You can check it at the coil connection spade, or closer to the switch itself. Would be worthwhile to check both.

I expect you will find a large variance in the voltage readings between "in" and "out" sides. If not, next step would be to check resistance. Reistance should be nominal (around 2.5milli-ohms per foot of length). Most likely culprits are the switches, connectors, or a break in the wire. Multistranded wire doesn't break really easily, so expect the first 2. You can check each component accordingly in isolation if need be (white/yellow wire, white wire, switch itself, etc).

If everything checks solid on voltage and resistance, check the coil grounds for issues. After that, assuming you still have the Lucas ignition, check the EI Box following the test proceedures outlined in your manual. In a pinch, you can find the test proceedures here (last couple pages):

http://www.classicbike.biz/Triumph/R...hop-Manual.pdf

Hope this helps!

P.S. Almost forgot, I would run your meter ground back to the battery and make sure it is a solid connection for the ground, otherwise everything else goes out the window. You can use a frame ground, but not always the best choice...

longlimb · 11-22-2012, 07:39 PM

Thanks for the detailed help RII. I really do appreciate it. I'll work on it this weekend hopefully.

Sent from my iPhone using Motorcycle.com Free App

longlimb · 01-30-2013, 09:30 AM

Ok. After many hours and many many cursing fits (new kill switch and throttle not the same as the old one), I got a new right handlebar switch assembly installed and low and behold I have almost 12v at the coils now. yay! Do didn't have to go through all the circuits and check everything, double yay!

So, tried to fire her up and actually got a short sputter after a couple kicks, then a couple backfires that kicked my leg back up on the kickstart arm (is that normal?). But then nothing. Kicked and kicked until I was dripping sweat to no avail.

So, how does the choke work on this bad boy? Attached is the pic of what I'm assuming is the choke. I have my finger on the lever. Is this a pump style choke where I need to just pump the lever a couple times and then let it return to the original position? Or do I just push the lever down and leave it in an "open" position until I get a start? Not familiar with this style.

I tried the pump method and then the leave open method but didn't work. Although I could have flooded it by then.