Spark plug grade mix

[zapo]

Somebody I know is running a zed with two B8's and two B7's - Don't ask - but I do follow his logic and my opinion is that if it works then go for it ( but maybe don't rev the balls of it too often).
Another opinion was that it's not a good idea, uneven heat blah blah.
Boring really but I wondered if anybody had a strong opinion?

[dave cullen]

Somebody I know is running a zed with two B8's and two B7's - Don't ask - but I do follow his logic and my opinion is that if it works then go for it ( but maybe don't rev the balls of it too often).
Another opinion was that it's not a good idea, uneven heat blah blah.
Boring really but I wondered if anybody had a strong opinion?

ok, I would like to jump in on this one, firstly, our own Ralph Ferrand recommends B7ES's for classic Kawasaki's on his website, secondly, having had an infuriating plug fouling issue on no 1 cylinder on my Z1100R, and having replaced carbs, coils etc etc, I ended up putting B7'S in nos 1 and 4 cylinders, and leaving B8's in 2 and 3.

The plug colours after a run now seem spot on, so wtf, having said all that, no 1 still doesn't like much choke on start up, but problem vastly improved.

Dave

[Pigford]

The 7's being hotter are said to ensure the new ethanol fuels burn better?

My A4 used to foul plugs, but I'm now using 7's in my A4 along with the "air corrector" kit that Rob (Zed1015) sells and the issue has gone away

It was also a common practice to run a colder grade plug in the middle 2 x cylinders on older air cooled fours back in the day, as the middle ones will naturally tend to run a bit hotter.

[rickm]

It was also a common practice to run a colder grade plug in the middle 2 x cylinders on older air cooled fours back in the day, as the middle ones will naturally tend to run a bit hotter.

Am I correct is saying that some of the old air cooled fours had larger main jets in the middle carbs than the outside two ?
Similarly, for one of my old bikes (think it was the GSX750ES) the workshop manual stated that when balancing the carbs, the middle two should be set 2cmHg lower than the outer two !
Presumably to work them a bit less and help keep them a bit cooler ?

[Garry.L]

It was also a common practice to run a colder grade plug in the middle 2 x cylinders on older air cooled fours back in the day, as the middle ones will naturally tend to run a bit hotter.

Same with the Two stroke Triples, ie fitting a slightly cooler plug on the centre pot.

Never read any Science on how effective or otherwise this is though.

[Pigford]

It was also a common practice to run a colder grade plug in the middle 2 x cylinders on older air cooled fours back in the day, as the middle ones will naturally tend to run a bit hotter.

Am I correct is saying that some of the old air cooled fours had larger main jets in the middle carbs than the outside two ?

Yes, that too for some bikes.

[dave cullen]

The 7's being hotter are said to ensure the new ethanol fuels burn better?

My A4 used to foul plugs, but I'm now using 7's in my A4 along with the "air corrector" kit that Rob (Zed1015) sells and the issue has gone away

It was also a common practice to run a colder grade plug in the middle 2 x cylinders on older air cooled fours back in the day, as the middle ones will naturally tend to run a bit hotter.

Agree on all counts, I reckon my R does have some problem maybe on that no 1 cylinder, but the hotter plug is keeping it more or less ok, and I can live with the occasional cold start problem

[needaz1100r]

Somebody I know is running a zed with two B8's and two B7's - Don't ask - but I do follow his logic and my opinion is that if it works then go for it ( but maybe don't rev the balls of it too often).
Another opinion was that it's not a good idea, uneven heat blah blah.
Boring really but I wondered if anybody had a strong opinion?

NGK themselves recommend using a one step hotter plug if you have fouling issues on a mildly used engine and have no other issues. They say it's to do with additives in fuel to make modern lean burn engines run cooler.

Don't forget the heat range of the plug is only of the plug, it does not make the engine run hotter or cooler, it still makes the same temperature spark, what is hotter or cooler is the tip of the plug, which should be hot enough to burn away deposits that want to stick to it (hence a hotter range if the fuel burns cooler and so doesn't heat the plug as much) and cool enough so it doesn't ignite the fuel just from the heat. It's still the spark that ignites the fuel and at start-up any heat range plug is cold.

[zapo]

Thanks for the replies.
I think I stay in the opinion of if it works, go for it.
In fact, as a knock on I think I'll try a set of 7's in my A4 - it doesn't foul plugs but always has black plugs with 8's in.

[dave cullen]

Thanks for the replies.
I think I stay in the opinion of if it works, go for it.
In fact, as a knock on I think I'll try a set of 7's in my A4 - it doesn't foul plugs but always has black plugs with 8's in.