Modern Vespa

The 'stock' plug spec is the B6HS, but they seem to be a bit harder to come by (longer shipping times) on Amazon (U.S.) right now. There are the resistor ones, the BR6HS. Would they cause problems? Is an iridium equivalent advisable/worth using?

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The non resistor plug is old tech that's going away. Get a non resistor cap. Just don't double up on resistors

Thanks. I've learned NGK has discontinued the B6HS and note the BR6HS as the replacement. Good to know there are other sources that have stock of the discontinued plug at a decent price.

I've read that resistor plugs used with old points systems are not recommended due to possible lower spark and subsequent incomplete combustion. Anyone have experience to confirm this?

Unless someone knows here, I guess I'll be reaching out to NGK directly to inquire if there's a *non-resistor replacement for the B6HS.

The old, non-resistor, plugs were used with resistor caps. As Grumpnut mentioned, you can use a new, resistor, plug with a non-resistor cap. The net result is the same, and the newer plug and cap are easier to obtain.

What you shouldn't do is use a new resistor plug with an old resistor cap. That would double the resistance in the system and could lead to problems.

That's good to know. Thanks.

Now I understand. Thank you..

Not right. There was no resistors at all. And there was no plug cap, just terminal and rubber cap. Same was on my: 1981 50 Special, 1981 P150X, 1982 PK50S, 1984 PK50S, 1989 PK50N. Also same was on lot of other Vespas that I serviced.

I have conversation with one experienced guy from UK and he adheres to the view of using spark plugs and caps without resistors, as was originally intended for these engines. TBH I don't remember why exactly and what his arguments were.

But now on my P150X plug and cap without resistors and there is also SIP speedo aboard and I have no any problems for more than 12000 km.
Same was with both parts with resistor or with any other combinations. Same on my PK S. And on my 50 Special there is non-resistor cap but plug is with resistor just because it seems that there no suitable non-resistor plugs for EGIG 170.

Hang on there Roland.

My US spec 76 Supers and US spec 79 P200 all came with these resistor caps from the factory.

Wild guess is the battery models were fitted with resistors.

SoCalGuy you are quite right. I have only seen one PX200 but there was Chinese aftermarket cap.

I also got this Grabor cap from an Vespa engine I don't remember. But is it OEM? And is it have resistor?

So what I'm hearing, the workable combinations are:

1. Non-resistor cap with non-resistor plug.

2. Resistor cap with non-resistor plug

3. Non-resistor cap with resistor plug

Yes?

In light of suitable non-resistor plugs phasing out of production, #3 would be the best short and long term solution (short of finding/waiting for B6HS plugs, or changing the ignition system). Yes?

Yes.

But non-resistor plugs is still producing)

Or....since the correct plug called out by the manufacturer is still in production, buy a dozen and never give it another thought for the rest of your life?

Thanks. I came across this that states otherwise.
https://www.ngk.com/ngk-7534-b6hs-nickel-spark-plug

Remaining stock can be found at some sites and auction platforms however.

I switched to non-resistance boots because it's much easier to find R plugs.

Buy whatever plug you want. Run whatever plug you want. It's your scoot and you know best.

Geez. Condescend much?

Now that's useful advice. Thanks!

I gave you a current source for the correct plug in my very first post. You didn't seem to want that. Out.

It was appreciated. I'm not very 'plug/cap(boot)-savy', but I'm continuing to learn.

Resistor caps and plugs appeared on U.S.A. models to prevent radio interference, but this was not the case on European models. A CDI ignition is designed to run without resistance, but on multi cylinder engines this powerful ignition causes light flickering, problems on radios (at least in the 80s) so it was mandated to reduce the intensity of ignition by installing resistors in plugs and caps. You will notice that 80s Honda Goldwing used a 10k resistor cap to reduce interference with onboard radio equipment.

Anyway, if you can avoid resistance do it. Use a 0Ohm cap, or wire clip, and find a non resistor plug. NGK is widely used but I really like Denso ND plugs and lately use them on everything since I got my hands on boxes of ND non-resistor plugs. Go on google and cross reference Denso to NGK plugs, there are loads of ND plugs floating around. They hold up really well, stay clean. I'm very impressed. On my px150 I got 6000 km from ND same plug before getting rid of the scooter and it was always clean and perfect.

Thanks. I resorted to NOS plugs off flea bay and switching to a Vespa wire clip that will give flexibility for plug types going forward.

Thanks for all the input here.