125-200cc SMS/WRE 125 Jetting problem. Help..

Hi. i have trouble with main jets. Since i unlocked my stock exhaust. I changed my main jet from 142 to 150, but spark plug is very bright. If i change clip position from 3 to 4 i have problem with power to 1/4 throotle and spark plug is still very yellow/white (?) is should be more brown. What should i do? Buy bigger main jest like 155, 160? i cant change clip position because if i change it to more fuel, motorbike have problem to 1/4 throotle - it interputts.

Sorry for my english. I need your help.

Its Husqvarna SMS 125 2008 with Dellorto VHST 28 and unlocked stock exhaust.

Oh sorry i forgot to add picture of spark plug. That s how it looks
On other forums people said it is too bright and i can have hole in my piston.

hi Matuesz

this plug is showing a dangerous jetting that can damage the motor, for sure you need more fuel and a bigger jet is needed.

when changing to a bigger jet you might change your clip position back to 3 or even 2

Robert-Jan

I put main jet 160 + clip on 3 position but motorbike has problem in full throotle (looks like too much fuel - it interrputs, chookes

Now i have 155 + clip 3 and everything looks okay, no more problem in 1/4 throotle and full throotle. Its really good

This is how my spark plug looks:
Is this color good? Because motorbike drives really good. And i dont want to change anything.

If your motor is driving OK and responsive then you achieved the goal

the plug looks in my opinion still a bit on the lean side but it could be the monitor settings of my computer.

Robert-Jan

that plug looks exactly how mine does, I thought the yellowish tip only referred to a high lead content in the fuel but I'm not an expert, my bike runs brilliantly how it is set up. Though I've got a br8 ngk in, not a br9