Information on TB42s extended rotor button

[Robo]

I found that this extended rotor button decreased the miss, but at the same time power fell away.
I put this down to less spark, the smaller the gap the less power is created to jump the gap.
and if you have a smaller gap at rotor and plug, power/spark energy drops, so I found getting a compromise here a matter of a few attempts at setting, and threw the ext rotor in spare parts container for emergency use. The engine never had the same power/torque with it fitted.

And here's a few tips.
Reason plug gap needs to be smaller for LPG, its dry, a wet mist from petrol aids the spark to jump the gap and hence the gap required needs to be wider for petrol, also to stop it drowning the spark.

I also run pertronic and iridium ngk 1 range cooler, swear by ngk, and think iridium's fine design also opens up the end of plug to expose the spark, and then there's the benefit of less maintance.

Also from memory pertronic say not to use HEI as it can damage pertronic unit.
The reason for running 1 range cooler is, LPG runs hotter as we know, so this aids to keep plug temps down.
don't let someone tell ya this equals less spark, this is not true, a cooler plug dissipates its heat better into the cylinder head, and a hotter plug physically stores more heat within its body. Hence the reason a car-boned up plug will create run on simply by the heat stored in the carbon deposits.
I've got 2 yrs out of this tune so far, think what I'm doing is on the money, but every engine behaves differently.
this on ngk's web site from memory about the heat business.

hope this helps.