What does my spark plug tell you

Just replaced my spark plug, it looks dark and wet to me does that means its running lean?

 

Its not the thread you should be looking at but the white ceramic and the point .looking at that it looks very lean

 

way too lean.

 

How do i fix this then? do i just adjust the idle screw?

 

You need a larger main jet. Does your bike have an aftermarket exhaust on it?

 

Why would I need a larger main jet when I haven't done any modifications?

 

i259.photobucket.com/albums/hh302/turbostang331/150carb1.jpg

Do I have to adjust the screw labeled low speed mixture adjustment? What are the rules and conditions for doing this? Engine running? Counter clockwise increases air flow richening the mixture?

 

Unscrewing the screw should make the mixture richer by adding more fuel. I would take it out 1/2 a turn and take it out for a short spin then check the plug colour afterwards.

That carb seems to be a copy of a Keihin diaphragm carb if I'm not mistaken.

http://www.scooterfocus.com/scooter_carburetor_adjustment.html

Hope that helps.

 

You have confused me there, i thought lean meant theres too much fuel and too rich meant too much air. So if i made it richer wouldnt i be adding more air to the fuel?

 

Okay i got that completely reversed so too rich means too much fuel and too lean means too much air? so my carb is running with too much air so i have to turn the screw clockwise to cut off a bit of air right?

 

I read that if a bike is running lean the end of an exhaust would be white but i have black soot or carbon shit sitting in he pipe, i run my finger inside and its wet and black shit,it doesn't smell so i assume its just condensation and carbon or soot idk if its running lean could that still be there? i notice this after starting the bike and riding it the 100 meters from the work garage to the front of the building and parking it.

 

The exhaust is wet with water (from the combustion of the fuel) and the soot is normal. I had assumed that your bike was a two stroke, when it obviously isn't from the type of carb the bike has.

You need to unscrew the idle mixture screw to richen the mixture, then adjust the slow running screw on the opposite side of the carb to get the idle speed back to what it should be, as making the mixture a bit richer may increase the idle tickover, just like putting the choke on a bit.

The diagrams in the link above should be close enough for your carb.

 

is it burning a lot of oil? im suspecting you have leaky rings and possibly you are running mineral oil? or semi sythetic?

 

also, does it feel a bit sluggish when its warm/cold from about 1/8th throttle to about half throttle? maybe cuts out every now and then?

 

Whats the definition of burning oil exactly? does that mean it burns and the oil level goes down or just blackens? my oil level is always the same from oil change to oil change but it does blacken quite quickly but i always suspected that its down to the fact i am always doing very short trips 2 mins to work 2 mins back 5-6 days a week and maybe a longer trip to the shops and back. In the winter it was a bit sluggish at the start but once it gets going it is fine even when its idling. When i first got it it once cut out at traffic lights but that stopped when i played with the idle screw a little. Never cut out since i played with the idle screw last year.

If i leave it to idle for 1-2 mins and then slightly turn the throttle by about 1/8 it is pretty sluggish, lack of power as i dont move then it sort of picks up and i move but it only does this sometimes and its hard to replicate, what does that mean?

It also does not seem excessively hot when running but thats hard to say because exhausts are supposed to be hot when running...

Yes i always use semi synthetic, no leaks.

 

your plug might just be that colour because of the short trips.... but sounds like you need to tweak the mixture screw a little, which is normal for those chinese 4t motors, also see how it goes with a slightly bigger main jet in there too. its normal that the engine oil turns black quite quick.

 

How will I know iv tweaked the screw just right? Is there an engine tone to look out for, I always thought my scooter ran a biy loud could the lean mix cause that loud roar I always tried to describe?

So you suspect my mix is lean so I should twist the screw clockwise to make it richer? and anti clockwise for leaner?

 

im not sure which way it needs turning for richer, just try a quarter turn either way and see how it feels. turn it a quarter and have a little ride down tyhe street, then turn it again and see how it feels......