What plug to use
 

The manual started either the denzo or ngk br9eg.
My ec300 went back for warranty work and it came back with a br8es!! I was told the mechanic says it will run a lot better using the 8es!
Can anyone shed any light on this?
I did run it today for a quick hour and it ran just fine by the way 👍

No clue what model year your bike is, 300EC 2018 and 2019 need a NGK BR8EG spark plug. a NGK BR8ES is not the right spark but it will work fine.

The EG type is the one with the thin center electrode while the ES has a standard center electrode. The EG is less prone to plug fouling and has (allegedly) a stronger spark hence better combustion.

As Doc Brown says...

BR8EG is the correct plug, BR8ES will work fine and no risk of damage to the engine. It's a much cheaper plug.

By the way...I always carry a spare new plug and plug spanner in my bum bag, just in case although I've never had to use it yet. :)

Sorry chaps it?s a 2019 ec300!

I e always used br9eg and that?s what the manual says to use. But like I?ve said, for whatever reason, the mechanic, who by the way races for gasgas uk advised to use br8es! 🤨🤨🤨

On NGK plugs, lower the number, hotter the plug. A hotter plug, as long as it doesn't cause a hot spot which leads to pre-ignition detonation, will foul less than a corresponding cooler plug.

The BR8ES and BR8EG are completely interchangeable. The only difference is in the electrode materials. Here is what I pulled on them...

S series plugs: These are standard plugs with copper cored centre electrodes. A copper core offers superior heat conductivity hence heat is removed from the firing end of the plug and 'hot spots' are prevented - these can lead to pre-ignition. A copper core also allows a longer insulator nose to be used - this protects against fouling.

G series plugs: These feature a smaller diameter centre electrode tip made of nickel alloy. The smaller diameter means a lower voltage is required to produce a spark. As the tip is made of conventional Nickel Alloy the service life is reduced. Best suited to applications where plugs are changed regularly.

That said, I have only used the S version plugs in all my bikes. That's Honda, Yamaha, Suzuki, Kawasaki, and GasGas bikes and I have never had a problem. That includes my old '74 Yamaha RD350 race bike I had many years ago. I tend to replace the plug once a year whether it needs it or not. Good jetting and a properly maintained engine are keys to good plug life.

If you are in Europe, the spark plug the manual says you should use is a NGK BR8EG. I wonder what owners manual you have, but for sure not the same I have.
If you are in the US, well, there may be a different owners manual though I see no reason for that.

This is a screen shot of my 2019 owners manual...

https://up.picr.de/35743745gn.jpg

In the UK...

BR8EG = 6 GBP
BR8ES = 3 GBP

G version is specified by GasGas but I've heard many people using the cheaper S version without any problems. I very much doubt anyone would see a difference in performance.

The S version is a standard spark plug, the G is a competition/racing spark plug which would be expected to be replaced more often.

Important points to note...

G version = Sparks at lower voltage, less prone to fouling, shorter service life, more expensive.

S version = Longer service life, can foul easier, cheaper.

If your bike is properly jetted and you're using a good quality 2 stroke oil I'm sure the S version will be fine, although as I said before I always carry a spark plug anyway!

I use the G and replace it yearly.

I have to stick my tongue out at F5 and say I've only used two BR8EG plugs in 8 years of operation. The original Denso spark plug was total garbage and only in the bike for a few weeks. I am on my third piston and second connecting rod.

Just out of interest, approximately how many running hours over the 8 years?