Plug fouling 350x

[Gunnar]

As most of you probably guessed Im not a motor head by any stretch of the immagination. Infact this is my first sport atv. Ive been pretty lucky with the Big reds.

So here it goes. My best guess is that its running rich, and keeps fouling plugs (they are black and sooty). It has a supertrap exhaust and a UNI filter. As far as I know that is all the mods. Float looks good, a hair under 3/4 in. with carb upsidedown. Air screw is turned 2 7/8 turns out. and has a 138 (stock) main. Needle is on the third clip.

In my train of thought this should make it run super lean. ?????? There is a small hole in the exhaust pipe back by the bracket where the rear motor mount/shock is and when its running it smells like its spitting out gas there, and cuts out when at idle and given a quick wot. Again its running rich right?

So where to start and how to fix this. Could this be causing the noise in the top end?

Edited for needle placement

[hazard]

put your needle in the 3rd clip position, if that doesnt help try the 2nd, i realize that if its on the top it should be making it lean, but its not evidently its not, heres a link, of vry good info, read carefully. http://www.duncanracing.com/techfaq/Tech_keihin-carburetion-jetting.phtml

[Liquid-Darkness]

That is a very good write-up on jetting.

[Gunnar]

Thanks for the site, and read jetting 101. Sounds like it could be lean. Its not hard to start, 3-4 kicks when cold. and does cut out when given a quick WOT. Not sure on the plug fouling.?
So can any one with similar mods, pipe and a filter, give me any ideas on where to start. Think I will change jetting in carb and see if I cant get it running good before worrying about the noise.

[Just_Randy]

Sure yer not burning oil??? I gave up trying to set my carb by looking at the plug due to the amount of oil I'm burning. I know you said something about a noise.... Piston slap???

[Gunnar]

It could be. From what I read running too lean can do some real damage to the piston. If it is running as lean as I am guessing it should be there could already be some damage there. I will get it richened up then go from there.

From what I read a 145 on the main and a 48 on the small aught to be a good place to start then work down.

[Gunnar]

I havent checked the slow yet but if that was upped then that could be where I am getting my rich plug from. I just got this and havent ridden it much at all. A few trip up and down the road and ideling in the garage. Ill check that today.

[Just_Randy]

When I first got my 230 quadsport it was blowing oil out the pipe! The sparkplug was caked with oil / gunk and wouldn't fire. I cleaned the plug and fired it up and it ran ok, but blew oil all over and fogged up the garage in a few seconds. So, I torn the engine down expecting to see a cracked piston or a hole or something to explain the amount of oil, but everything looked sorta ok except for a few small scratches on the cylinder wall and piston skirt and the oil rings where wore down pretty good. The piston was still tight in the bore too. Took it down to the suzuki dealer n asked what they thought n they said it was the oil rings. I don't know how that much oil got past the top 2 rings in such amounts to pool up on the piston like a bridbath, but I guess it did.

Anyway, I guess the moral of the story is you don't need that much wear to burn oil. If you're at the point where noise is heard from the piston skirts slapping on the cylinder, you would have to be burning some oil. Moreover, you'll have lots of fun tuning the carb like that.

[Gunnar]

I will be doing a compression check And putting it on a timing light before replacing jets. Hopefully all that checks out OK