Black Spark Plug

[qiknis]

Before any "bolt on" mods to my 400 I could run WFO and not overheat the engine. After adding WB E pipe, WB Rev, Dyno Jets and K&N I have overheating problems. (I think)

Main is a 170, air lid off.

While crossing a salt flat south of El Golfo, wide open, my bike died. I waited several minute and restarted the machine. 5 miles later the same thing, this time 5th gear and 1/2 throttle.

I pulled the plug and it is black. Not a wet black, but a very dry black. There is some oily looking black stuff on the threads.
The link below provides a picture.
http://members.cox.net/steve.poeppe/images/sparkplug.JPG

If I put the air lid back on, will that fix the problem? From what I have read i'm running lean? Does that mean reduce air intake? or install a bigger main jet?

Thanks,

Steve Poeppe

[cals400ex]

if the plug is black, your too rich. i would lower the mainjet down to a 155 or so.

[cals400ex]

also, you could be rich on the needle clip position.

[qiknis]

Ok, I'll drop the jet and repost with the results.

Thanks for the info!

[Evan400ex]

Go with a 160 on your main since your using dyno jets. I have used a 155 main and it was to lean.

[qiknis]

Drat, I just finished installing the 155. I'll put in the 160 tomorrow.

Thanks,
Steve

[cals400ex]

Originally posted by Evan400ex
Go with a 160 on your main since your using dyno jets. I have used a 155 main and it was to lean.


i think the 160 is going to be too big. the dynojets run a little bigger than keihin jets. also, your running built engine, he just has a pipe and filter. i would think the 155 or 1 size smaller would be the trick. i just said 155 so you didn't run it lean.


where do you have the needle clip at? are you running the washer under the needle?

[Evan400ex]

I ran the 160 dyno jet when I had the stock bore and the 155 was to lean. The 160 ran perfect. I run a 170 with the built engine.

[cals400ex]

i guess everyone jets a little different. i don't even run a 160 on my built bike unless it is in the dead middle of winter where there is a bunch of cold, dense air. by the way, i use keihin jets.

[coo-beans]

could need oil to ever think of that

[cals400ex]

Originally posted by coo-beans
could need oil to ever think of that



:huh you lost me??