black plug

[Patrick_Krivacka]

I wrote a little bit about this in the 'post up your gas mileage ' thread, but I decided to start a new thread here, so as not to spin that one off too much. Anyway, I've got one plug that looks pretty good, tan. the other one as of yesterday was black and smelt of gas. I lowered the needle one notch, rode it to and from work today, and checked it when I got home. It's now dry, but still black. the soot is very dry, and easily wipes off. what does this mean?

[montmil]

Rich.

[nhmaf]

It is running rich - though this could be from too much gas OR too little air.
IS the throttle response good (engine accelerates strongly without "hiccups" in the 4000 - 6000 RPM range?  When you've been riding around for a bit, come to a gentle stop in a fairly flat place, put bike on centerstand and take off the float bowl from the bottom of the carb, carefully.    How much gas is in it?   Top of the fuel line should be about 6mm down fromthe top or a bit more, I think, more or less.  If it is too high, (floats are sinking or float needle not shutting off fuel flow) that can also cause rich running even if the needles and jets are OK.

[Patrick_Krivacka]

I thought black and wet was rich and black and sooty was something else. anyway, it runs really well. no flat spots. I'll try taking the bowl off. How long do I need to ride before looking?

[Mike V]

iman,

I wouldn't worry too much about it right away as long as it's running well. Get some good miles on it and have another look after some spirited lengthy rides. Even though the metering rods shouldn't have too big an affect on the idle and mid-range circuit, someone may have tried to balance the carbs with unequal metering. If it's smooth and pulling equally I would just ride it a while and deal with the details later if any may exist. You may be totally fine the way you are. Are they the same plugs you're reporting about or fresh ones?

http://www.dansmc.com/spark_plugs/spark_plugs_catalog.html

This chart is an old one, when gas was gas. Don't put too much weight on the color of your plugs these days as the addittives can give you false indicators in relationship to the 70's. But this will give you a guide.

[Patrick_Krivacka]

yeah, I'm mostly curious and trying to keep any serious damage at bay. They are new plugs. It can't be air, as both sides share a common filter and as I've said, one side looks fine. I think I'll pop the float bowl off tomorrow after riding it home from work and see what that tells me.

[Barry]

I thought black and wet was rich and black and sooty was something else

Black and wet would be oil contamination. Rich is black and sooty.

Use of the choke can cause black and sooty which will then not easily burn off.  Putting clean plugs in a warm engine would get around this.

 A little soot on the base ring of the plug is normal. If you still have real black and sooty then it's rich but which circuit ?

idle, needle/needle jet or mains.

Engines are set up to run richer at idle and unless your riding flat out all the time then the majority of your steady speed riding is being done on 1/8 to 1/4 throttle where the idle circuit and transfer ports are still making a contribution to the mixture so that's where I'd start

The float levels are important and at least they need to be set equal both sides. I use 22mm depth of fuel measured from the central well.

Idle is easy enough, Turn in the mixture screws until it stumbles and then back out enough to make it run clean again. Beware of  "and another 1/4 turn out" which you will see recommended in print, maybe the width of the screw slot at most.  
 
For the mid range you can keep dropping the needles until you loose power.  It will be obvious when you've gone too lean.

Mains are unlikely to be excessively rich if the correct size and you wouldn't be seeing a difference side to side.

[steve hawkins]

Which side is the sooty plug.  Do you use the side stand?

Just a thought

Cheers

Steve H

[Patrick_Krivacka]

that's a very interesting reply, steve. i had thought the same thing. I do leave it on the sidestand a good bit, and it is that side.  do you think that's it? seems reasonable.

[Lucky_Lou]

I think Steve has nailed it for you try not to use the side stand too much or not at all if possible and see how you go, you can get alot of oil in the cylinder especially if you use the side stand when the engine is running then switch it off.
Lou

[Patrick_Krivacka]

I think we've nailed it. It runs really well, so it seems odd to me that it would be so black. I'll try keeping it off the center stand for a few days/weeks and see what that brings.