Tiger 750 Wiring

[natej3]

I’m putting a Tri Spark ignition on my ‘73 Tiger 750 and could use some experienced wiring help. I removed the condensers and wired the coils as per the Tri Spark instructions, but I’m not getting any spark. I have only had the bike for about a year and the last owner completely rebuilt it. Much of the wiring appears to be original but there are clearly some new wires. I linked the black/white wire that is probably the original wire from the the auto advance unit (now the Tri Spark unit) to the negative terminal of coil 2 and linked the black/yellow wire from the Tri Spark to a white/yellow wire that I assume comes from from the ignition. There are two other white/yellow wires that were originally attached to the other coil so maybe I got that wrong. I am attaching a pic of the coil wiring from before the Tri Spark install. If anyone has thoughts on what I should do, please let me know. Sure, I could trace all the wires and map it out, but that would take forever. I’m hoping someone has seen this before. Thanks,
Nate

 

[Rudie]

Tri Spark ignition
not getting any spark.
pic of the coil wiring from before the Tri Spark install.
the last owner completely rebuilt it. Much of the wiring appears to be original but there are clearly some new wires.
I’m hoping someone has seen this before.

As you have posted you have changed the wiring, a photo of the wiring before you changed anything does not help.

I have seen similar before. Regrettably, the obviously-new wiring in your photo is poor.

A 73 Tiger 750 is nearly fifty years old. Connecting brand new electronics to fifty year old electrics is not plug and play, even if d.p.o. (Dreaded Previous Owners) have not been screwing with the electrics.

I could trace all the wires and map it out, but that would take forever.

You are the one with a not working bike. Fifty year old anything requires more work for the pleasure than brand new anything. If you are not prepared to put in the work, you are not going to have the pleasure. The internet can give you advice that will reduce the amount of work but, before you know what the problem/s is/are, any 'advice' is speculation that you have to work through.

The alternative is find someone local to you who really does know (not just says he knows) in this case about old British electrics and pay him handsomely for his knowledge.

If you are prepared to put in the work:-

. Buy a multimeter. It is an essential tool for all sorts of electrical work on the bike so buy one that has a cast iron guarantee that it has electro magnetic interference (EMI) protection. The rip off merchants in the US selling cheap meters are not prevented from selling ones without EMI protection.

. http://www.classicbike.biz/triumph/Repair/1970s/73-78-Triumph-Bonneville-Tiger-Workshop-Manual.pdf is the workshop manual for your bike. It is free to read online or you can buy in brand new from a spares dealer.

. The wiring diagram for your bike is on pdf page 190/manual page H21. Use your new meter and the wiring diagram to eliminate "probably", "assume", etc. from the sentences in your first post.

Tips:-

. Certainly while the engine is not running, the battery is the only source of electrical power on the bike. If an electrical component is not 'working', start testing from the battery.

. Any electrical component must be part of a circuit - you must be able to trace both a supply to the component from the battery and a return from the component to the battery.

. Apart from the alternator, any electrical component uses Direct Current (DC) from the battery. DC supply is always from negative (-ve) and return is always to positive (+ve). It is counter-intuitive but that is how it is, just get your head around it. Any information containing the word "ground" (aka "Earth") should be treated with great suspicion until you can ascertain what the writer actually meant (which is often "baffling with bullshit" rather than "dazzling with brilliance" ).

. As much of the wiring looks original, know that the original Lucas company that made it incorporated a network of Red wires between almost every electrical component and battery +ve. These are not shown in any wiring diagram but they are the primary electrical return, not the frame or other random bits of metal attached to the bike.

. Because of that, I do not follow a Tri-Spark wiring diagram when connecting the Red wires:-

.. The Red wire from Tri-Spark "Coil 1" +ve terminal should be connected to battery +ve.

.. The Red wire from "Tri-Spark Stator Unit" should be threaded alongside the existing Black/White and Black/Yellow wires out of the engine and also connected to battery +ve. For this, you will need especially thin wire - 9 Strand PVC Wire. British Wiring is the only US supplier of European-size wire and the Lucas terminals matching those on your bike already.

.. Also ensure there is a Red harness wire attached to the engine.

 

[sikatri]

Sometimes the simplest route is the longest. Informative post Rudie, tampers my enthusiasm for a “classic” project slightly. Must be prepared for some tedious work.

 

[natej3]

Well, I traced down the immediately pertinent wiring. It indeed is wired as per original, ie black/yellow, black/white, and white/yellow go where they should. And Rudie was correct about the poor grounding in the Tri Spark recs—that was apparent even as I was setting up the timing, as the red indicator light acted erratically until I changed the ground. So thanks, that made a big improvement. Oddly, though, only the left cylinder is getting spark now and that is with either coil. If I crisscross the plug wires so that the left coil runs the right cylinder i get the same result—no spark on the right (I’m testing that with a timing light).

 

[Rudie]

Well, I traced down the immediately pertinent wiring. It indeed is wired as per original, ie black/yellow, black/white, and white/yellow go where they should.

This is not clear. Do you mean these wires are still connected as for points:-

. White/Yellow from handlebar kill switch to each coil -ve terminal;

. Black/White from drive side (left hand looking towards the front of the bike) coil +ve to points and condenser;

. Black/Yellow from timing side coil +ve to points and condenser?

If so, White/Yellow, Black/White and Black/Yellow wires must be repurposed exactly as shown in the Tri-Spark wiring diagram.

Real life underseat implementation of Tri-Spark wiring diagram:-

. The two White/Yellow wire terminals pulled off the coils -ve terminals and the two Black/Yellow wire terminals pulled off the timing side coil +ve and condenser terminals:-

.. either connect each White/Yellow wire terminal to one of the Black/Yellow wire terminals;

.. or connect one White/Yellow wire terminal to one Black/Yellow wire terminal and securely tape up the unconnected White/Yellow wire and Black/Yellow wire terminals.

. The two Black/White wire terminals pulled off the drive side coil +ve and condenser terminals

.. either connect both to the two drive side coil -ve spade terminals;

.. or connect one wire terminal to a drive side coil -ve terminal and securely tape up the unconnected wire terminal.

That makes the drive side coil "Coil 2" according to the Tri-Spark wiring diagram.

For testing, the Black wire with the blue insulated terminals in your photo can be used temporarily as the "Link" between Coil 2 +ve terminal and Coil 1 -ve terminal. The reason it should be used only temporarily is it is poorly made - the terminals shown are known as "Bodger's Terminals" (I never use them except for temporary repairs on other people's electrics), the ones in your photo are the wrong type, size and have not even been crimped properly.

Aside and as I have posted already, you are connecting modern electronics to fifty year old wiring. So make new electrical connections as good as possible. British Wiring in the US sells correct spade terminals, Lucas bullet terminals (starter kits of both) and bullet crimping tools; regrettably, they do not sell a correct spade terminal crimping tool (not pliers or vise grips) but should be able to advise a source. Also regrettably, particularly the tools are not cheap in the US (can be cheaper from the UK despite p&p but without allowing for any import taxes).

only the left cylinder is getting spark now and that is with either coil. If I crisscross the plug wires so that the left coil runs the right cylinder i get the same result—no spark on the right (I’m testing that with a timing light).

Once the wiring is connected correctly - matching the Tri-Spark wiring diagram and my advice - if the problem persists, try swapping the spark plugs side to side and/or for new.