Trident 750 Warning Light?

Remove the fuel cap and check venting and then the tap and related pipework and check for anything that's cutting fuel supply.

 

To be honest, that sounds like a fuel issue or the choke would make no difference at all.

In your situation now I would

1) run the bike till it stops, then pop the fuel cap open and listen for whistling noises, turn the fuel tap to prime ( ie straight up ) and apply inward pressure to the tap.

Then assuming still no start

2) pull off the tank and check the coil resistances, that should give you yes or no answers.

If no definitive answer

3) remove and clean the carbs including "T" piece filters, also check the spark plugs colour & condition

 

Yes it might, but be careful to earth the plugs well as damage is possible to the coils.

Tank will need to come off for this anyway ......... just a thought is the foam heat barrier at the rear of the head on your Trident fitted ? if not get one and fit it as this is a common fault with causing coil failures as its meant to stop heat blowing back onto the coils and cooking them.

Item 25 here
https://ie.fowlersparts.co.uk/parts/10653/trident-/bodywork-55072

 

Its the ignition amp that gets damaged by not earthing plugs, and i am really surprised that the coils are prone to heat failure, most cars run coil on plugs sat right on the top of the motor so pretty much heat prof...why can they manufacture bike coils the same?

 

Actually in this model of Triumph its the coils that fail, followed by the crank position sensors..... And coil on plug was used on later models but these were built with standard parts common to the whole range when triumph started up.

The model under discussion was one of the original models that rolled off the line when triumph first started production over 20 years ago, and no they didn't get it all right but compared to some car manufacturers that have been at it for far longer they have done a cracking job so far

 

I was actually talking generic in that most CDI ignition systems its the amplifier that gets damaged from not earthing the plug when triggered, also cars have been running coil on plug for the last thirty years or so, which is why i mentioned it,
i have Lucas Rita CDI ignition on my 1975 trident, and the Rita is pretty much from that era but unfortunately it still runs oil cooled coils, its not like solid state coils where not available even back in the mid 70s its a shame that Triumph and Lucas didn't take a leaf out of the Japanese makers books.

 

In that case if you have checked the fuel cap vent i would start by changing both the vacuum and fuel hoses for new , and try an get hold of another fuel tap to try ...or just change for new, or non vacuum tap that's the only way to eliminate those components from the equation.

Just to actually prove the problem is fuel supply related after running for the half hour, and if the carbs have drains on the float bowls you could just drain one carb down into a container immediately after it stops and measure just how much fuel you have, and compare it to a pre start amount if its the supply then there is likely to be less than normal.

 

Ok so it looks like a vacuum issue, fuel taps are available but expensive at £60+ or you could fit a repair kit its possible the diaphragm inside the tap is porous but you should be able to prove the vacuum issue by leaving the tap set to prime and running the bike, I have done this from start-up several times without causing other problems.

Does your low fuel warning light work ?? if not you will need to keep a close eye on mileage and fuel amount so you don't get stranded.

Changing the vacuum line is a good idea too, as is fitting it to a different carb top to eliminate the possibility of a crack in the spigot opening under temperature as it all heats up and losing the vacuum which holds the tap open.

1) Try running the bike with the tap on prime only

2) Move the vacuum connection to another carb

 

I make kits to covert to pencil coils. Much more reliable.
PM me if you are interested

 

Are they Audi coils by any chance?

 

No. I did a lot of research to find coils with the correct resistance. If wrong can burn out your igniter.

 

Interesting, most CDI coils have a primary resistance of 0.2 to 3.0 ohms, HT resistance is usually what kills ignition amps, but they are usually pretty pretty tolerant and anywhere between 6 and 30kohms but resistor caps and plugs add to this, you're more likely to kill the amplifier by not earthing a plug, what sort of value are those coils then?

 

I'm more mechanical than electrical. My friend who knows electronics well said which ones i use. And that what works for me. They are in my own bike and many others, so that's what I stick to. Tried many that had different parameters. Which were rejected.

 

I cant find it on there ?

 

This is what you need. Along with a short extension and a swivel joint, to get the middle plug out. https://www.ebay.co.uk/itm/303652572062