All 2st Spark plug electrode melted

Hello. I have SMS 125 2t and i got problem.



I have unlocked diffuser and put new main jet - 155 (was 142)
Motorcycle looks like it is good regulation and spark plug was brown so mixture was good.
And i did 2000km since last spark plug check and now i saw that electrode is melted :/
I have no ided why... It isnt poor mixture i think.
Compression is 9,5atm
What to do?

Sorry for my english..

photos:

https://zapodaj.net/images/2b1a112d21f29.jpg
https://zapodaj.net/images/23b62be9bb224.jpg
https://zapodaj.net/images/345f894e25ebd.jpg
https://zapodaj.net/images/de0d169b94b33.jpg
https://zapodaj.net/images/30dc058d9915f.jpg

Looks like pinging or preignition. Was the engine "rattling" at times while you were riding?
What heat range plug are you using?
Are you using high octane fuel?

Whats pinging? I dont think its preignition bec it works really good. Good acceleration, no problems with start etc. and i didnt touch ignition.

Spark plug is BR9EG.
Nope, im using normal fuel

2000km earlier spark plug was like that:
just a bit darker bec it was at 150 main jet, now i have 155.
was it good? or poor mixture

That last plug looks fine. All you've done since that plug was used is change the mainjet from 150 to 155?
Have you changed how you ride perhaps, more full throttle maybe?
How's the coolant level?
Pinging usually only occurs when the engine is under heavy load (eg. hard acceleration). It sounds a bit like stones rattling in a tin can coming from the engine.
If you can't solve this, You may want to consult a motorcycle workshop and let them have a look. Whatever the cause is could cause massive damage to you engine if left unresolved.
Good luck.

yea, that was all i ve done.
When i was testing plug was diring full throttle and slowly. I need to see how will spark plug looks after that.

Now i ride mostly on "small open" throttle, and about 15% in resonance.
Its not pinging
Of course i have cooler full of liquid.
Sometimes when it was really hot outside engine and difusser was "burning" my leg.

I bought new NGK plug same as earlier and will check how will plug look to see mixture ratio.
I heard that poor mixture can melt plug but that plug looks good...
And what do you think about too high temp? I was riding when it was aroud 35 celsius degress so maybe then it melt plug? But it was just some days so it is possible to melt plug in maybe 200km?

I would at least pop the head off for a look ! if the piston looks eroded around the outer edge its detonation - Was it a proper main jet? some of the ebay items are made in china ect and while being fine if you jet your bike properly with them the numbers are nor always comparable with oem. ie a 155 may be a 140 - been there before and couldnt work it out on a old dellorto

i hate reading plugs...waste of time. jet for best performance

This main jet is really good.. Its not from ebay or alli, from good online shop in my country.
Its original dellorto jet for my carb...
So i dont know what to do..
I ordered new BR9EG and maybe i will ride 20-30 kilometers and check how will this spark plug look.
But if it will be looking good - dark orange or something like that i have no idea what to do next.
Maybe change my spark plug from racing to normal? Will it be less temperature?

Should i buy bigger main jet? like 175 or 180?

Actually on jest 165 spark plug is still white.

at wide open throttle....increase main jet size until you get "four stroking"...then lean 1 size...
this is 2 stroke tuning 101..if you want it jetted safely. stop looking at the plug.. go by performance..

that is, unless there is another issue going on making you run lean.
two strokes do not like constant small throttle openings. no fuel/lube for engine