An update on my hard to start ST

[Sibbo]

Tilly has been very hard to start for a while with no obvious cause ,it took a handful of choke ,wind , wait 5 minutes and hold face correctly ...... and no obvious reason .

It turns out her twin plugging setup ,coils etc was set up 'in parallel' , the local bloke changed it to 'in series' and she is away . Double the spark I suppose .Anyway she starts and runs very well on a cold morning now ...not that I get cold mornings ...so, cool mornings .

She doesn't run as smoothly at low revs as she did but the starting is the main thing .I wasn't game to overnight anywhere !

Happiness is a bike that starts when you need it !

[ME 109]

Ah, good to go for the Alpine then eh' Sibbo. Brindabella next year.

I think there will be some questions asked about your find. I haven't got any, wouldn't have a clue.

[Major Softie]

Yep. More info.

Is this is still an R80?

What is your dual spark/ignition setup?

What else on the bike is not stock?

What work have you done recently before the problem started?

[ME 109]

Yep. More info.

Is this is still an R80?

What is your dual spark/ignition setup?

What else on the bike is not stock?

What work have you done recently before the problem started?

Well, that about wraps it up.
Sibbo?

[Sibbo]

Yep. More info.

Is this is still an R80? Yep ,completely R80ST

What is your dual spark/ignition setup? I don't know ...sorry I'm no mechanic .

What else on the bike is not stock? Fuel tank ? The strange rear shock I can't identify ?

What work have you done recently before the problem started? Set valve clearances , balanced carbs . New plugs ,new plug leads ... made no difference, removed small amounts of corrosion from coil connections .No improvement in starting although she ran better .

That's it .

[Sibbo]

Yep. More info.

Is this is still an R80? Yep ,completely R80ST

What is your dual spark/ignition setup? I don't know ...sorry I'm no mechanic .I think it a couple of Japanese coils .She runs very well once started .

What else on the bike is not stock? Fuel tank ? The strange rear shock I can't identify ?

What work have you done recently before the problem started? Set valve clearances , balanced carbs . New plugs ,new plug leads ... made no difference, removed small amounts of corrosion from coil connections .No improvement in starting although she ran better .

That's it .

[sterob]

" Sibbo said:
It turns out her twin plugging setup ,coils etc was set up 'in parallel' , the local bloke changed it to 'in series' and she is away ."
I'm no expert on dual-plugging or ignition systems but,
If they were in parallel, they would each receive maximum voltage and, I would have thought, the best possible spark. When i series, they would have to 'share' the voltage, and one may 'share' more than the other and cause a weaker spark on one side.....
Am I wrong with these observations?

Sterob

[Sibbo]

But now she starts easily from cold ...why ?.

[chasbmw]

It may be relevant that these bikes ignition is wasted spark. Eg all four plugs fire at once, I can't remember how the ht leads should be set up on dual plug bike, but I think that the 2 leads from each coil should be split between the 2 cylinders, eg one coil does top plugs the other does bottoms. It can also help if the bottom plug runs one heat grade hotter than the top plug to help burn off oil fouling because the bottom plugs (esp the LH one if you use the side stand) can get fairly mucky.

It's good that you are getting it sorted as one of the joys of a dual plugged bike is that they start so easily.

Charles

[Ken in Oklahoma]

I'm no expert on dual-plugging or ignition systems but,
If they were in parallel, they would each receive maximum voltage and, I would have thought, the best possible spark. When i series, they would have to 'share' the voltage, and one may 'share' more than the other and cause a weaker spark on one side.....
Am I wrong with these observations?

I believe that the usual setup for dual plugging is two twin fire coils whose primaries are wired in series. That is to say that the two coils are 6 volt coils each firing two plugs. Thus for each ignition event all 4 plugs will be firing at the same time.

It is conceivable, I think, that two coils, whether single fire or twin fire, could be successfully used wired in parallel. In that case they would need to be 12 volt coils rather than 6 volt coils. The primary resistance of each coil (impedance would be a better word) would be twice that of equivalent 6 volt coils. The energy going to each of the 4 plugs would be the same as with two 6 volt coils in series.

There was a thread not to long ago on the subject. I think it was me who contended that two 12 volt coils ought to work just fine in an airhead ignition as long as both coils are operating within their design specifications. There was one point made, if I recall, that one coil might "steal" the voltage/current from its neighbor. My response, again as I recall, was that 12 volts (minus whatever voltage drop there might be across the points or solid state electronics) means that the coils are operating within the design parameters and they, because they are good dutiful coils, must provide the requisite spark.

I believe there was another comment about the dynamic interaction (firing transients) between the coils? That I simply don't know about, which is why I say that the two 12 volt coils "ought" to work just fine in parallel.

That concern goes away, of course, with two 6 volt coils, whether single fire or twin fire, connected in series.

Because more total energy is needed to fire 4 plugs rather than two, points don't seem to be up to the task, and that's one reason why an electronic control unit, or whatever it's called, is needed.


Ken