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[Bullet Whisperer]

What I actually mean is, I [personally] don't see the need for anything other than the most basic of plugs for the most basic of engines. Even the Enfield racers I built and maintain just have plain old B8ES/HS plugs fitted, if they fire every other stroke, that will do for me. Regards, Paul.

[Scalyback]

[center]
I use that brei8x something plug in tornado, my 500 bullet and it seems fine.



I got no resistors on Kevin the meteor minor and the bike works well, but it don't half screw up the radio on my workbench when running!

[Rattlebattle]

So are the terms resistor and suppressor synonymous here? I had always used the latter term. I also understand that it's best not to use suppressor caps or plugs on magneto equipped bikes like my Tiger 100. B*gget the neighbours tv interference I say...

[Leon Novello]

Yes, resistor and suppressor are the same; as are capacitor and condenser the same; condenser being an older term which persists in motoring parlance.

[Rattlebattle]

Thanks; thought so. I still call them condensers too in that application. Must be an old timer....FWIW I have changed the plug cap on my C5 town on-resistor type and also use a non-resistor plug (BP6ES). Anti-social me? At least I've kept the standard exhaust. With the plug gap at 0.5mm it runs very nicely now.

[neddy]

Have used an Iridium plug for a while, don't think they are worth it on this engine, did not notice any difference to the old type at all

[Tim NZ]

Unleaded petrol DOES NOT colour spark plugs!


Never has, never will!




Internationally, leaded petrol contained up to .45g of tetra-alkyl lead per litre, though typically the levels was between .2 and .3g per litre. As well as increasing the petrol’s Octane rating, and acting as a valve seat protector, it also acted as a catalysis that burnt off carbon residues from spark plugs and helped to keep them clean. Along with the ‘lead’ were organic chlorides and bromides which further prevented excess fouling of Plugs and lead oxide deposits on piston crowns. None of these ‘scavengers’ are present in unleaded petrol.
The typical density of unleaded ‘Super’ petrol world wide is 0.750 Kg per Litre, compared to 0.735 Kg per L for leaded petrol. The higher density of unleaded petrol provides greater energy content per litre, but requires a slightly LEANER air-fuel ratio to maintain the correct chemical balance during the combustion process. In the real world this equates to a 1-2% change.


In use, the surface of Spark plugs is slowly coated with amorphous carbon, this is more so when the plug temp is below 200c, or the mixture is too rich. If it remains on the plug for periods of time, it is gradually converted into graphite; a good conductor or electricity, and also a ready absorber of water vapours. Such plugs will slowly build up increasing layers of carbon fouling, frequently wet in appearance, though not always, and are highly prone to misfiring issues. At plug temps between 200-400c, the fouling no longer accumulates, but neither does it dissipate. With out Lead in Petrol you need plug temps of between 400-500c to start to see this residue ‘burn off’ and keep the insulator clean.
The removal of Lead oxide, corrosive scavengers, and Lead from petrol has also removed the ‘self cleaning’ properties from petrol. No longer are there the coloured shades of yellow-orange-brown that once used to build up as a glaze on the central porcelain, the former generally accepted indication of ‘optimal’ air-fuel mixture. Which it never was either, it simply indicated optimal Plug operating temps!

[Leon Novello]

Hi Neddy: You won`t notice any difference in performance, they make a spark like any other plug; maybe easier kick- starting, maybe all in the mind too. The advantage is they will last a lot longer, justifying the extra cost, so you are not always buying new plugs. As I said before, a smear of anti-seize on the threads, do not alter the gap or clean. Fit and forget.

[jefrs]

The "BR" resistor or suppressor in the plug or that in the HT cap (but not both), is not there just to reduce radio interference. By placing a greater load on the HT coil it is supposed to provide a better spark. The HT coil is a transformer, when you change the load on the secondary, you will alter the output voltage. The idea is to provide a big fat spark. It may seem counter intuitive that placing a resistor in series with a spark gap will increase the voltage but that's what it is supposed to do.

[jefrs]

I used anti-sieze copper grease on plugs in my TR7 car. It ejected one of the plugs in most spectacular fashion and had to be helicoiled. I then discovered that the copper, with a little electricity to help will corrode aluminium in a very effective manner. The aluminium becomes a sacrifcial anode (typically zinc, aluminium or magnesium).