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Hi, Guys. Been some time since I visited as not used Triumph this year until yesterday. Anyway As with many others who have one of these (1960 5TA Speed Twin with a distributor) It has a tendency to run poorly. I have swapped out most electrical parts last year and a new UK made coil seemed to help. Last night I was reading a thread on here from some time ago and it was mentioned that the AC from emergency can cross with the DC from battery? Hope I have that correct? Anyway what I have found is that when my battery is not fully charged the bike seems to run better but after 5 mins or so it starts to play up. This is with the ign in the normal position. If I fully charge the battery on a charger it seems to play up straight away? When the bike is playing up if I switch my original PRS8 (or something like that :) ) switch over to emergency apart from a slight hick as I pas the off position there is absolutely no change and it runs just as poorly. It does feel like what you get if you start your bike in emergency start and forget to switch back to normal when battery becomes fully charged as should happen to let you know. Also if the battery is fully discharged I am not able to start the bike ever in emergency. I am now thinking that maybe as was mentioned the AC side is crossing with the DC side? and if this is the case would a simple case of removing the AC wire from the switch confirm this ? :smile2: and if so what wire should I remove? If the bike then runs OK but with no emergency start I would think this would point to a fault in the switch. Also if that works could I try then reconnecting the AC wire and removing the DC wire so the bike runs and starts in Emergency but not on normal ?
I may have this all wrong as electrics are not my strong point :)
It is still running as it was made with a 6 volt system. The wiring loom was new and fitted before I got the bike. I fitted the main PRS8? switch as the one fitted was a modern one and all terminals had corroded. The one I fitted looked in very good order for its age with brass terminals and no obvious signs of a crack. I am 100% sure I have all the wires in as per wiring diagram and all lights and horn work as they should. Hope you guys can help.
 

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AFAIK the PRS8 used a weird system? ( my experience is with cubs/prs8s)

I think that as you switch on lights, the PRS adds additional coils from the alternator into the equation to balance up the current drain?
What happens when you combine the 6v wires together to get 12v, yet retain the light switch, I don't know.
 

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Hi,

I am 100% sure I have all the wires in as per wiring diagram
Mmmm ... which wiring diagram? The one in Instruction Manual No.4 has misprints that affects the charging when the lights are off ...

thread on here from some time ago and it was mentioned that the AC from emergency can cross with the DC from battery?
Hope I have that correct? Anyway what I have found is that when my battery is not fully charged the bike seems to run better but after 5 mins or so it starts to play up.
If I fully charge the battery on a charger it seems to play up straight away?
1. Link the thread.

2. I don't know if it's possible on your bike but it is possible for AC leak across the rectifier. It isn't impossible that the symptoms you describe are due to AC leaking into the DC wiring. But, equally, the symptoms could apply to the battery being simply overcharged ... because the "wiring diagram" you followed is the one in Instruction Manual No.4 ... Or it's just a dud battery ...

if this is the case would a simple case of removing the AC wire from the switch confirm this ?
Aiui, no; it's a case of the leaking AC has done damage that is manifesting itself; even if you disconnect the alternator stator from the rectifier, the damage is done. :(

John Healy ("johntioc" here) has posted a test method for AC in DC; if he doesn't chip in, maybe send him a pm?

I may have this all wrong as electrics are not my strong point
Mmmm ... don't go for exotic theories like "leaking AC" 'til you've checked the simple stuff ... like dud batteries, misprints in wiring diagrams, etc. ... :D

Btw, if you don't have a multimeter, beg, steal, borrow or buy one. I suggest buying - you'll need one at least capable of measuring Ohms (resistance, might be just a horseshoe-shaped symbol) and both DC and AC Volts - and John might suggest an AC ammeter; that I'd borrow.

PRS8 (or something like that )
PRS8 is a combined ignition and lighting switch; later superseded by the 88SA, which are separate ignition or lighting switches.

AFAIK the PRS8 used a weird system?I think that as you switch on lights, the PRS adds additional coils from the alternator into the equation to balance up the current drain?
Mmmm ... yes and no.

The alternators are permanent magnet, so the magnetised rotor is inducing electron movement (generating electricity) in the stator coils any time the engine's running.

If you have a wiring diagram that has all the wires and connections it should have (i.e. the bike maker's draughtsman didn't make any mistakes when he was supposed to be just reproducing the wiring diagram Lucas supplied :rolleyes:):-

. Lamps off, any of the switches used with 6V electrics (PRS8, 88SA, 41SA, etc.) short-circuits the two 'lighting' (stator) coils pairs; this generates a magnetic flux that actually depresses the output of the 'ignition' coils pair, that's supposed to prevent overcharging of the battery.

. Pilot/tail lamps on, the aforementioned short-circuit is broken, the 'ignition' coils pair generate more, allegedly to match the draw of the lamps on.

. Headlamp on, then the output of the two 'lighting' coil pairs are used to supply AC, ostensibly to the headlamp.

What happens when you combine the 6v wires together to get 12v, yet retain the light switch, I don't know.
"to get 12v":-

. You specifically "combine" (connect) the stator Green/Yellow wire to the Green/Black wire; the latter's already connected to one side of the rectifier, so you're rectifying the whole output of the alternator stator (Green/Yellow is connected to one end of the two 'lighting' coils pairs, Green/Black is connected to one end of the 'ignition' coils pair, White/Green is connected to the other ends of all three coils pairs).

. You also disconnect all the wiring between the stator AC cables (either at the rectifier or between the stator and the rectifier) and the ignition/lights switch; i.e. no short-circuiting stator coils, emergency starting, etc.

. Either you connect a Zener diode across the battery or you replace the rectifier with a modern combined electronic reg./rec.

It is still running as it was made with a 6 volt system.
Note you can do the aforementioned three things and retain 6V. The DC Volts is dependent on the regulation; as standard, it was essentially the battery; now there are modern 6V combined electronic reg./rec. as well as 12V. :thumb I'd be happy to supply more details if you're interested.

Hth.

Regards,
 
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