Is It The Coils?

I had problems starting my '98 TBS yesterday, it's been firing up fine all winter but took a good while before bursting into life yesterday.
Then, once warm, it cut out as I came to a stop a couple of times and again took a while to fire up.
I had stopped and restarted it a couple of times without issues between times.
Also, there's been a slight hesitation/delayed throttle response for a while now. It feels like it bogs down before the revs pick up.
Is this the coils, and the starting problems are the coils getting worse?
Any advice would be appreciated, as I have no idea, other than reading whatever pops up from an internet search.

 

How old is the fuel? The most volatile fractions will have evaporated off over winter making for harder starting and slightly reluctant running.

Any obvious misfire?

 

Fuel was 2 weeks old.
I wouldn't describe it as a misfire (burning guess it could be), more a hesitation when opening the throttle.
Seems fine above 4k revs.

 

Let it run for 12 mins, or untill the fan kicks in, after starting, without touching the throttle. That resets ECU

 

Failing ECU reset it sounds suspiciously like the symptoms I had with a Gill coil on its way out on my Bonnie. Since you have three coils the trick is to buy one replacement and identify the culprit by substitution. PVL 1290007 is the one you want.

 

Cutting out when hot and re-starting only after cooling down for a while are classic symptoms of a failing crank position sensor, which is not unknown. But I've not heard of it affecting cold starting so other causes should be considered, as per the above suggestions.

 

Cool, I'll give this a try. I assume it's OK to use the choke?

 

Absolutely. Only affects your carburation. Both the coil and crank sensor are coils with very fine copper windings. Over time they are prone to break but often go intermittent before total failure. The coils proper provide each cylinder with their spark while the sensor sends a pulse to the ECU to trigger each spark at the appropriate point of rotation.

 

I should have said from cold.

 

Give it a goodly slug of Redex or similar which will clean out the fuel system especially the carbs which may have a bit of muck in them. My Trident was hesitant on its first ride out after winter lay-up a few years ago. A dose of Redex cleared it within a very few miles. Can't do any harm!

 

Thank you gentlemen.
A bit of reading up and thought makes me think that it could be the crank position sensor.
If it was a coil, surely it would still run but on 2 cylinders? Not cut out completely. Or would it?
This sensor doesn't look as easy to replace as the coils though!

 

You might think so but they can stutter inconsistently before dying for good. Got a multimeter? If you unplug the crank sensor lead under the side cover/adjacent the battery/air box you should get just under 600 ohms resistance from one side to the other. If you cannot locate the connector dress making pins through each lead will get you in. Tape up holes afterwards. Likewise each coil should measure something like 18k ohms from plug lead socket to the grounding earth where it mounts to the frame.

A ‘1’ (infinity) is open circuit and your culprit but sometimes only substitution provides definite proof. The crank sensor is the easiest place to start. It certainly sounds like a coil acting up as it gets warm.

 

Would one coil acting up cause it to cut out completely?
It only happened when I came to a stop, just died instead of idling. And then took a while to fire up again. But not so long that it had cooled down.

 

No. That is a big, fat, wagging finger pointing at the pickup coil.

 

https://www.triumphparts.gbr.cc/product.php/2927154/

Right model?

 

Yep, that's the one.

 

Does anyone know, or able to find, the correct air gap for the pickup coil?
I can't find it anywhere!

 

Thank you.
I've set it at 0.75mm, which appears to have been a perfect guess!
Ride in the morning to see if it's cured the problem.
The old one was over 1mm, not sure what effect that might of had.

 

Only for efi bikes. A TBS only has an igniter not an ECU and does not do adaption

 

So.....
Started perfectly from cold, very little amount of choke needed. Ran smooth until warmed up, then was a bit hesitant/lumpy at low revs occasionally. Not sure if I should just get new coils too. Or if it'd just a characteristic of an 20 year old carbed bike.
Seems to have cured the stalling issue though, and started fine when warm.