a spark plug thread - "best" spark plug for a triple?

i put  pentronixs flame throwers in my 750 after the last rebuild, bike ran like shit and of course i never equated it with a bad coil as it had "new coils" in it after all - after checking everything time and time again i decided to put the old bosch back in and the bike ran perfect - so while they may be good coils apparently they do have some failures too 
Paul LeClair said:
Hi Andy

that was a few years ago, I ordered the coils in from a local auto speed shop, in black bodies, they were either 40,000 or 45,000 volt output, and they were exactly the same body diameter as the original Laverda 750 Bosch coils. I just peeled the stickers off the black bodies, mounted the coils in the original location on the original clamp mounts, only real tell tale for a rivet counter would be that the coil top was black rather than the brown of the Bosch original. Wolfgang even sells the appropriate Bosch coil stickers if you really were determined to disguise the modification...

Paul LeClair
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Paul LeClair said:
My rudimentary understanding is that a ballast resistor typically reduces the 12 volt feed by 3 volts, down to 9 volts.
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Hi Paul.

To be pedantic it's not voltage that cooks coils, but the current through the coil and its duration. The duration (dwell) is much better controlled in modern electronic ignitions (it's actually user-programmable with the Ignitech). So coil or ignition unit overloading seems to be less of a problem than it was. The coil can be charged for each firing cycle at a higher voltage (and current) for a shorter time. So the energy fed to the coil is kept to a minimum.

The original purpose of ballast resistors was to facilitate starting. Using a 9V rated coil means it will still fire OK whle the battery voltage is depressed during engine cranking with the starter motor. During cranking, the coil is fed by a jumper wire from the starter relay, which bypasses the resistor. When the engine starts and the starter motor is disengaged, the coil is fed via the resistor, thereby maintaining its 9V supply.

I've occasionally wondered why Laverda chose coils that needed a ballast resitor, but never wired in a bypass feed from the starter relay.

Another reason for the resistor dates back to the days of points ignition. When the ignition is switched on, and crankshaft is in such a position that the points are closed, then current will be flowing continuously through the coil, in which case it'll get quite hot. A resistor will help prevent the coil cooking under that condition.

A good electronic ignition won't switch voltage to the coils until it receives an input from the pickup. The key word here is a "good" ignition system. The Dyna electronic ignition on my Guzzi energises both coils as soon as the ignition is turned on. I didn't realise until I was fiddling around with the electrics and had the ignition on for a few minutes. I happened to touch one of the coils and nearly burned my hand! Leaving the ignition on for any lengh of time will cook the coils and flatten the battery. I would have expected better from a company with Dyna's reputation and prices.

Cam
 
Rusty Spokes said:
I'm sure if the aftermarket HT coils needed a ballast resistor..they would of specified it in the installation instructions. I don't think splitting a HT wire from a single output coil for a 180 will work very well. Dyna makes the dual output coils, illustrated below. Redax is right..the big Dyna coils are bulky but do fit..the mini Dyna coils would be a good choice. They claim about 40,000 volts per output.

Wolfgang sells the Dyna coils..don't know if he has the mini series. Dyna coils are pricey..but if your changing spark plugs often..they are worth it.

coils.jpg
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I have had the big green 3 ohm Dyna coils on my 79 1200 since around 2000 or so..... really high tech mounting system of black zip ties and a chunk of dense foam stuffed between the two coils to keep them from bouncing around... :o

at retail the Dyna coils are a little pricey, but there is a Dyna coil dealer on eBay.com who sells them for slightly over half price and reasonable shipping.. I am wondering if the Dyna mini coils are the same voltage or higher voltage than the original bulky green coils? The mini's definitely would be easier to mount.

for my suggestion of using single output auto coils on a 180, I didn't mean to split a high tension lead from one coil, I meant using three coils, and wiring two of the coils to fire at the same time for the two outer pistons, each coil obviously having one high tension lead, the only wire "twinning" would be to wire two of the three coils to fire at the same time like a double coil also would...

Paul LeClair
 
Maurice, have you tried self lighting party candles ,they never fail,your kids should know some good suppliers :D

Shaun
 
One example of a dual output automotive coil is that for the Citroen 2CV which always fired both cylinders at the same time so wasted spark!

No idea whether they would be anywhere near useful for a 180 clunker, but you never know.

You could always rephase the crank to 120 "while you're at it", use three coils and get a better engine...  (bolt)

:):):)

--
Dick
 
Since modern fuels have rendered plug chops an unreliable method of tuning..............I now run without.

(Well it is Friday==========>Beer)

H.
 
The ballast resistor issue has been covered before...it isn't switched out on starting. John Wilson surmised that it was specified by Bosch to avoid wrecking the ignition amplifier boxes if the system was connected to out of spec third party coils. As such it is redundant when used with 3 ohm or greater coils.

The stock ignition always pushes current through the coils when the ignition is on. DMC - and I suspect similar systems - switches the current off if the engine isn't cranking after a few seconds. It also reduces current draw when running by minimising the on time (when the coil is energised).  This means that such systems don't need continuously rated coils and something like the Dyna mini will be suitable. 

Finally, just because a coil is rated at 40kV doesn't mean it will fire the plug at that voltage.  The system will only use the voltage needed to jump across the plug gap. Typically this will be a quarter of that value!
 
Ah another Citroen man amongst us now your talking....Be careful though if thinking of sourcing coils from a 2cv as a lot were 6volt...

By the way Triumph used a dual output coil along with some of the bikes from the land of the rising sun.

 
Brett said:
Ah another Citroen man amongst us now your talking....Be careful though if thinking of sourcing coils from a 2cv as a lot were 6volt...

By the way Triumph used a dual output coil along with some of the bikes from the land of the rising sun.
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Yeah, just about every pre-COP 4-cylinder had 2 of 'em.

piet
 
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