Fouling.The needle jet may be worn and its running too rich. What colour is the exhaust pipe.! If its black, put the needle down a couple of notches and try it.
wellabolla,
Nov 3, 5:58am
Its two stroke so the exhaust will always be black and oily! It could be a worn needle issue! also make sure you are using the correct plug.what type oil are you using in the fuel And another fault could be in the coil or mag.if its a little weak in the ignition area,the spark may not be grunty enough although i would have thought it would be hard to start and maybe "misfire" under load
pettal,
Nov 3, 6:51am
Throw the NGK plug away and get a Bosch or Champion= I have found NGK's tends to foul easier than you would expect .
jetted too rich, what are your jets numbers and are they the standard ones for that bike!the bike may have been jetted for low elevation compared to your potential high elevation for example, or an agressive rider who could ride it hard enough to keep his poor jetting at bay
ceebee2,
Nov 3, 6:47pm
I owned brand new 2 stroke M/C's for years and actually found Champion were far worse than the NGK for longevity generally.
jimdaddy,
Nov 3, 10:10pm
bump.from what ive seen isnt 40 to 1 mixture pretty rich!
klark,
Nov 4, 12:07am
If its standard jetting then it needs to be changed. Factory fitted #370 main jet is too rich, its generally used for running in and and soft sand riding.
It should have a spares kit with alternative safe jets in it to use. Needle should be set to the 3rd position from std, make sure the clip hasnt been moved all the way to the bottom.
There is nothing wrong with the standard NGK R6918B-8 plug, it will serve you well, if it doesnt then it tells you something else is wrong. Do not fit cheaper alternatives, they fail.
Theres nothing rich about your 40:1 mix and Yamalube choice, thats a good mix with a good oil. Make sure its not your RH crank seal sucking in engine oil.
Lack of compression is a common cause of your complaint, if you are getting oil dripping from your muffler at 40:1 with yamalube then you will need to freshen up the motor with a new piston and ring. When was it last done! There are a lot of compression gauges out there giving wrong readings so get it double checked and test with the throttle wide open, but it shouldnt foul plugs at 200-210psi.
johnf_456,
Nov 4, 2:08am
I agree had the same, even air craft use ngk.
rlr29,
Nov 4, 7:55am
Is it smoking! White smoke when Idle! Cold/Hot!Crankcase/gearbox seal! oil usage!New piston!
keeptightningme,
Nov 4, 8:06am
Good way to checkthe crank seal, if it is useinggear box oil, the crank seal is leeking.
jimdaddy,
Jan 30, 11:43am
yeah sorry i got confused for a sec there.
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