|Posted on Tuesday, August 04, 2009 - 12:51 am: ||
We were all taught in auto shop how to read spark plugs; basically, black/sooty is too rich, white is too lean, tan is Just Right! Well, I changed my plugs Saturday...just because....and was shocked to see the electodes were an ashy white, which would indicate a too-lean condition. The bike is running strong, no lagging hesitation or popping, even on decel....I tried adjusting the pilot screw, but it started bogging so I re-set it where i was (about 2-3/4 turns out; Mikuni HSR 42).
Stranger yet, the M2 Service Manual says that a yellow, white or tan electrode indicates proper and complete combustion. Huh???
Bear in mind, the SM was written for stock M2's with CV40 carbs & Helmholtz.
Buell race header & muffler
Buell CF air filter
Andrews N8 cams
As I said, it was running great. So, what color are your plugs?
I figure i'm either;
a) making a mountain out of a molehill, or;
b) destroying my pistons and valves
|Posted on Tuesday, August 04, 2009 - 05:11 pm: ||
mine are the same way and I had it on the dyno with the sniffer and it is running a bitch rich? I was confused too, I thought it was to lean. The only thing you can do is put it on the dyno and see where it sits.
|Posted on Tuesday, August 04, 2009 - 10:56 pm: ||
Funny thing is, the inside of the tailpipe is sooty-black...an indication of a rich mixture. And it certainly runs that way, too. I stuck a ColorTune plug in the front cylinder and the flame was a nice blue...not cobalt, as the CT manual says is optimum, but not yellow either. I'm confused..
|Posted on Wednesday, August 05, 2009 - 12:09 am: ||
Oh yeah, almost forgot to mention...I'm running the 10R12 plugs instead of the 6R12's......
|Posted on Wednesday, August 05, 2009 - 05:39 am: ||
The plug looks ok too me. you may want to try a cooler plug if your concerned and a dyno sniffer will answer all your questions.
|Posted on Saturday, August 08, 2009 - 12:32 am: ||
Mikuni tuning guide sez....
1) If the best idle is achieved with the air screw less than one turn out the pilot jet is too small and should be exchanged for a larger one.
2) If the engine speed does not slow after two and a half turns out, the pilot jet is too large and should be exchanged for a smaller one.
Sounds like I'm right in the ballpark; at least on the idle-1/4 throttle circuit..
Read about it here: