T160 Ballast Resistor/zenor Diode

[Duck749]

Ok, looks like I have most of the wiring traced and marked/confirmed for what it is. The bike has Boyer ignition and looks to still have the positive ground setup. One thing I noticed is previous owner had no turn signals installed so flasher unit and such is missing.

My question is around the ballast resistor, both wires look to be tied together and the resistor removed. The bike doesnt have the starter installed, do I need the resistor with or without running a starter? I see this is often bypassed to help with a strong spark but not sure requirement with Boyer ignition and with/without starter.

When looking at the zenor diode, one of the wires connecting to it looked frayed and poor connection. The front cap from heat sink is also missing, which may tell me it was serviced at some point. When connections are poor or diode is bad, what symptoms occur? I read online that it resulted in poor performance with back firing and such when on throttle.

I am really hoping things can be this simple. The owner had a big bore kit installed and ran into issue with center sleeve dropping in head. The head was pulled and re-machined, shortly after the bike had reoccurring symptoms like initially. He suspected the sleeve dropped a second time then it was put away in 80’s. Maybe I am lucky it just needs a diode, versus entire head job, then again I don’t know specific issues he was running into.

Thanks for any help or info.

 

[Rudie]

bike has Boyer ignition
ballast resistor,

Ballast resistor only required with points. Originally was in series with each ignition coil, because they are 6V and the rest of the bike's electrics are 12V.

Coils are connected differently to most electronic ignitions, ballast resistor not required.

zenor diode, one of the wires connecting to it looked frayed and poor connection.

The Zener has a number of wires connected:-

. Brown/Blue are negative and connect battery -ve terminal to rectifier, Zener and one ignition switch terminal;

. Red are positive and connect the Zener to battery +ve, possible via other components;

... it would help to know which are "frayed".

 

[Duck749]

There is a wire mounted to bottom which traces (continuity) back to positive battery. I cannot see wire color yet until remove tape around it.

There are then two brown/blue wires connecting to it. One of the wires appears to be soldered to end and the other wire is hanging on by a few strands.

The two brown/blue wires trace and have continuity back to battery negative which is also brown/blue wire. This also has continuity through rectifier. Additionally there is a dual connector from harness with brown/blue they also have continuity with. According to workshop electrical diagram this looks to be common connection which tied diode (#17) with electrolytic capacitor (#38) which wasn’t standard.

Here is a picture of diode and wire by battery.

 

[Duck749]

Rudie from comments in another post you replied to, I also recognize need to upgrade the brown/blue wires. My thinking is now that I understand what I am dealing with, need and have, I can begin some cleanup work.

I would look to test and or replace diode and upgrade wire size. If I can get electrical working a compression test would be done. This will help me determine if there is a real sleeve drop issue prior to just pulling head off if I don’t need to.

 

[grandpaul]

Rudie from comments in another post you replied to, I also recognize need to upgrade the brown/blue wires. My thinking is now that I understand what I am dealing with, need and have, I can begin some cleanup work.

I would look to test and or replace diode and upgrade wire size. If I can get electrical working a compression test would be done. This will help me determine if there is a real sleeve drop issue prior to just pulling head off if I don’t need to.

You don't need a single wire, ignition, coils, or battery on the bike (working or non-working), to conduct a compression test.

 

[Rudie]

cleanup work.
upgrade the brown/blue wires.

How I would clean up the wiring:-

. As I suggested in an earlier thread, as the bike does not have an electric starter, but is still positive ground, I would move the main fuse to a single 28-strand ("14 Gauge") Red wire connected to battery +ve; I would also make the fuse a 15A blade. Depending on the age of your bike, ime it has either one or two 14-strand Red wires on a ring terminal for connecting to the battery +ve terminal; cut off the ring terminal and connect this/these wire/s to the other side of the fuse holder from the battery with either bullets and a snap connector or male/female spade terminals and insulation (all available from British Wiring).

. Fuse moved, single 28-strand Brown/Blue wire direct from battery -ve to the ignition switch, not via the rectifier and Zener diode.

. Single 28-strand Brown/White wire from battery -ve to the rectifier DC- terminal and the Zener 3/8"-wide spade terminal. I would put another 15A blade fuse/holder in this wire close to the battery -ve terminal but it is not essential.

Reason I advise:-

. 28-strand ("14 Gauge") wire is: even the original alternator is rated for 10.5A @ 5,000 rpm but original 14-strand wire is only rated for 7.5A and even the modern metric 14-strand is only rated for 8.75A, either exceeded by the alternator output around 2,500~3,000 rpm ...

. Separate wires for connecting battery -ve to ignition switch and rectifier/Zener is: if especially the Zener fails, replacements are not reliable, better will be to replace both with a combined regulator/rectifier. As that will connect separately directly to the battery terminals, the (suggested) Brown/White wiring can be removed along with rectifier and Zener, there will not be any unused connections in the new 28-strand Brown/Blue wire that will require insulating.

test and or replace diode

Ime, Zeners are reliable until they fail.

Easiest test is once you can run the engine:-

. connect a Voltmeter or multimeter set to Volts across the battery;

. well calibrated meter, fully charged battery, meter should display 12.6V when everything switched off, maybe slightly less (-0.1V?) when ignition switched on;

. start engine and raise rpm slowly, Volts should rise with rpm to 3,500~4,000 rpm and 15V max.;

. continue to raise engine rpm, Volts should remain steady, should only fall when engine rpm falls.

If the above test works, Zener is fine; apart from wiring cleanup, I would not change it, unless you are considering upgrading the alternator (which is a different question ).

 

[Duck749]

As I suggested in an earlier thread, as the bike does not have an electric starter

Would the suggestion for how you wire change if the electric starter stays? Would that only change the fuse setup?

 

[Rudie]

Would the suggestion for how you wire change if the electric starter stays? Would that only change the fuse setup?

The standard electric starter 'grounds' through its mounting to the engine, that is the reason for the thick cable from an engine mounting bolt to battery +ve.

Because of the thick cable from engine to battery +ve and the harness Red wires connection to a cylinder head bolt or stud, there should not be any Red wire connected to battery +ve. So the main fuse has to remain in the Brown/Blue wire connected to battery -ve.

As I posted earlier, Lucas did originally put one or two Red wires to connect to battery +ve in harnesses. The problem with that is, if the thick cable is not reconnected to battery +ve (after servicing?), because the harness Red wires are also connected to the engine, when the starter was used, it 'grounded' to battery +ve through Red wires, damaging them and the harness. A NVT Service Bulletin of May 1975 instructed disconnection and insulation of any Red wires connected to battery +ve.

 

[Duck749]

I certainly have some upgrading that needs to be done. The +VE did have a single red wire from harness connected to it, there is a fuse on the -VE side.

For the ground wire from +VE to cylinder head or stud, is the .28 strand enough or should this be heavier gauge (like current automotive ground wire)? My existing red wire that is on the +VE, can I just find a frame bolt near the battery box to install that or how did the factory install it after the service bulletin?

I do have an order in with britishwiring for the thicker wire recommended, enough to keep me busy for a while!

 

[Rudie]

Risking repeating myself but for clarity:-

The +VE did have a single red wire from harness connected to it, there is a fuse on the -VE side.
the ground wire from +VE to cylinder head or stud,

. Electric starter not present or connected - new single 28-strand Red wire between battery +ve and the bolt or stud through a rocker box and the cylinder head with the existing harness Red wires connected to it; main fuse (15A blade?) in this new wire.

. Electric starter connected:-

.. No thin Red wire (original 14-strand or new 28-strand) connected to battery +ve; only the thick starter return cable should be connected to battery +ve.

.. Because the other end of the thick starter return cable is connected to an engine mounting bolt and the existing harness Red wires are connected to a bolt or stud through a rocker box and the cylinder head, the Red wires connect to the thick cable through the engine. The thick starter return cable is the return conductor to battery +ve for all circuits.

.. Because no thin Red wire connected to battery +ve, the main fuse must remain in the Brown/Blue wire between battery -ve and the ignition switch.

the ground wire from +VE to cylinder head or stud, is the .28 strand enough or should this be heavier gauge (like current automotive ground wire)?

The "28-strand" sold by British Wiring is rated for 17.5A - each strand is 0.3 mm. o.d., the total conductor cross-section is 2 sq.mm.

My existing red wire that is on the +VE, can I just find a frame bolt near the battery box to install

Would not serve any useful purpose. The Service Bulletin assumed electric starter connected so advised any and all Red wires disconnected from battery +ve should be taped into the harness securely.