Re Jet - Spark Plug Color By epdowd (Read 1,654 times)

[epdowd]

I know this is an old story but I have read about all the info I can find here, so I'll have to explain and ask :
My scoot has the 157QMJ 150cc engine. I removed the airbox, kept all the hoses in their original connections, put on a Unifilter and it ran Lean, it ran a bit Rich prior to the Uni Filter.. The original main jet was 100, so I tried a 115 and then a 125. Both tests were done with a standard NGK plug gapped at .032 and an NGK Iridium plug gapped as it came out of the box. After running for five miles on each plug the ceramic around the electrode is still nice and white on both plugs.(should be brown?) The difference is the ground strap on the standard NGK is an ashy white , while the ground strap on the Iridium plug is grey with a black tip.
I am useing 91 octane gas at 3500 ft.
Should I go to the 135 jet or look else where ??
It runs perfect at idle, mid range and WOT,, it is fast !!
Thanks a lot..

[Alleyoop]

How did you check the plug after running it at WOT. If you ran around then drove it back home nice then checked that alone will change the color of the plug. You have to run it WOT for a bit then Cut the engine and pull over and pull the plug, otherwise the tests will be off.
Another way to tell if your running LEAN look at your Header Pipe if its BLUE your running LEAN. It should be turning a little Bronze Color.
Alleyoop

[Bashan]

AO is correct, that's the ideal test. However, if you're running great you're dialed in very close and I wouldn't get overly worried about it. I've talked to Dr. JR about this quite a bit a he feels if you're not having performance problems, ride it a while and then pull the plug and make sure it doesn't look hinky. The absolute ideal color for a plug is tan, here's a nice chart:PLUG COLOR CHART Also, mileage is a factor, really crappy mileage means you're probably way too rich. Mine runs a little powdery grey and no matter how much I tweak it to try to acheive the ideal color, it stays right about there. Any other thoughts out there? This is one of those topics like which kind of oil or gas, a gazillion opinions. By the way, I don't think there are "old stories" in scooterdom, there's always somebody seeking that particular answer, and they're fun to talk about over and over anyhow. This is a hobby, it should be fun, people get way too wound up and critical. Rich

[epdowd]

Thank you AO and Bashan. I have been useing the NGK Plug example chart and I'm pretty close to the correct color, just concerned about it being too white. I'll give it the test you mentioned, also put a few more miles on the scoot. I only have 178 mi. on it..I wanted to get it right before I put all the panels back on..The valves are set at .004 and .005.
Thanks again..

[epdowd]

I just did the WOT test. Had about two miles on it then stayed WOT for a while, Hit the Kill switch and pulled over. The ceramic is maybe a light grey and the ground strap is grey with black tip. I think I'll keep it as is..