plugs are yellow?

[bigborebanshee]

Never seen this before in all my years of tuning 2 strokes,When the engine was run WOT with new plugs,it had a darker smoke ring that was obviously a little fat on the top end.The engine ran good on the bottom and the little brown spot near the insulator tip shows. It pulled ok through the mid,but instead of a brown color,the plugs are actually yellow and glossy.No heavy build up,just yellow coloring.The engine would misfire under heavy load at low and high rpms.

 

These plugs are after 40 minutes on a MX track

 

 

 

Edited September 13, 2010 by bigborebanshee

[EvilBanshee]

Are you using a different fuel then before???

[drag+6blaster]

looks like low octane fuel . Did you let your fuel sit for a while before burning it ? Mite have went dead

[bigborebanshee]

Are you using a different fuel then before???

 

I am using Sunoco 110,i was using VP 110.

[camatv]

high octane fuel will burn yellow or orange. first time it did it to me i freaked out also!

 

its not from low octaine they'd deto hard in a cub with domes requiring a high oc fuel.

[bigborebanshee]

high octane fuel will burn yellow or orange. first time it did it to me i freaked out also!

 

its not from low octaine they'd deto hard in a cub with domes requiring a high oc fuel.

 

I put bigger domes in to bring the compression down to 150 and ran pump gas through it,plugs look normal and its not misfiring anymore.I think the 110 was too much for the 160psi and +4 timing i was running.Im half tempted to put the smaller domes back in and run it on pump gas to see if the misfire comes back.

[AKheathen]

lol, that's plug glazing. if you throw an igniter on them, they'll spark down allong the insulator, insteard of across the gap. what causes it is deposits, like separated oil, or unburned leftovers form the high octane fuel. when you pull hard, it heats them up quickly and glazes the deposits to a conductive coating. it can also happen from the wrong heat range. either you were too rich on the bottom to heat them up and keep them hot, or you just need less octane. rule of thumb is 165psi and +4 is safe for pump, but it really depends on cr/elevation. what setup, bore, porting, and dome size are/were you running? pipes, too.