BR8ES VS. BR9ES

[Lowflying]

I have an '85 RZ250 with a 350 top end, 350 carbs and oil pump.

Haynes manual for 350 says use NGK BR8ES. My mechanic reckons the BR9ES are a better choice for my bike. What are you guys using and whaddya reckon?

Thanks,

Robbo.

[2TInstitute]

ES plugs are for lawn mowers

[Lowflying]

Great. Can you elaborate?

[ds6user]

Hi Low flying.

From my experience with two strokes and plug heat ranges, the higher the number, the better the performance. But higher number more likely to foul up when cold starting. It.s not an issue for me as plugs can be easily changed when warmed up.

As for the "ES" have no idea, but if the Haynes manual says to use them, they are most probably not too far off mark. Have a look at genuine owners / service manuals or NGK plug Book.

[Lowflying]

Thanks for the input ds6user.

I'm a bit confused about something. From what I've seen on the NGK site, the 8's are "hotter" than the 9's. So wouldn't the 8's have less of a fouling problem then?

[Jeram]

Have a look at a BR8EIX perhaps

[2TInstitute]

Great. Can you elaborate?

Yes except I cant type for a full day non-stop. The Iridium is much better plug. If youe having to throw plugs at a bike there is something wrong with the tune. Which is usualy a combination of ignition and jetting. The RZ ignitions are not known for being the best. Next is the coil.

[ds6user]

Hi Low Flying.

Youre on the money. The Lower the number the less likely to foul up.
Never have got my head around "Hotter" and "Colder" terminology anyway.

Just to confuse matters more, mine uses B9HCS plugs. The "C" seems to denote the champhered end of the plug, thus giving a smooth contour to the combustion chamber. A minor point but might give 0.05% more power. On mine, every bit helps.

[EPApolice]

I ran the iridium plugs in my KR1 track bike and noticed no difference what so ever over the stardard ES ones. No worse but no better, that's money better spent on tyres.

[2TInstitute]

Your not meant to notice the difference with iridium plugs, what iriduims will do is take less voltage to fire the plug and the fine wire sucks less heat from the flame kernel. That amounts to easier starting and longer life, especialy(where the KR1 is concerned) with marginal igintions.
With proper race plugs the dyno shows a clear gain, my ear does not decieve me, the sharp 'crack' of the exhaust note only comes with the platnium/iridium plug.

[EPApolice]

Well in the real world I noticed no difference at all, starts the same runs the same and if I had a few extra hp on tap it would be more than welcome at Eastern Creek up against R1s etc. Perhaps when I fit the new motor it might be different.

[2TInstitute]

Pat it's a arrow head the closer you get to the pointy end the bigger difference small things make.The more the engine is optimised the more likely you will notice the difference. Have had a YZ82 make 0.5HP across the range with a race plug, not much but show me another bolt on mod for <$50 that can show the same improvement on a dyno.

[EPApolice]

Every bit helps