YZ250 2004 driving me insane

[Aftermath]

This bike is driving me insane with the splooge coming out of the exhaust. I am at 6000ft above sea level, so jetting needs to be pretty lean, but how lean can I go. I've changed to a leaner needle @ (2nd Clip), 42 Pilot and a 168 Main. Air screw out at 1.5 turns. as you can see, everything is leaned out, bike runs great but at the end of every ride (Unless it's cold), I have a thick line of black splooge running down my exhaust and dripping onto the swingarm. I've even replaced the oil seal in case it was trans oil getting into the cylinder.

Have I reached the point where I must accept the above, or at my altitude, can I go even leaner. I mainly do woods riding with a bit of MX every now and then. Help, help help........

 

[Rcannon]

This may not apply to your 04, but I never could get my older yz to jet properly at higher (5000) elevation.

I finally gave up on it. Somewhere along the line I rebuilt the top end.
I found a chipped reed. I replaced it and it helped some.

A year or so later I had the head milled. Instant fix. At the higher elevation we also lose pressure inside the motor. The head milling brought it right back where it needed to be. The bike was easy to jet from then on as well.

Another thing to look at is this. The rich condition really relates to heat.....or lack thereof inside yoru engine. Are you riding it hard enough? If the bike is jetter dor light trail riding and you suddenly end up in sand, is this goign to be a problem for you???

I dont have my 06 jetted perfectly yet. I have had better success with the 06 using the jd jetting kit needles. They are rich enough in the proper place to prevent the pinging that can show up on these bikes, yet not so rich as to screw everything up.

The best way I have found for jetting is to mark the throttle like Eric Gorr suggests....1/4, 1/2, 3/4 and so on. Even though it sounds so basic, having the throttle marked helps a ton in determining just where yoru jetting is rich.

That oil could be caused by a rich pilot, and the top end is perfect. (just an example, not to be confused with the truth!)

 

[Firedude]

Did you cleanout the pipe and change the packing before you started jetting? You may be good with jetting and have enuff left over spooge in there to keep it coming out for awhile.

 

[KX02]

Aftermath,
I am at about 1000ft. and my jetting is pretty similar to yours, so yes, I think you could go leaner. I normally run a 42 pilot and a 165 or 168 main with James Dean needles. Of course my bike is not a YZ but same carb and engine size.

 

[Aftermath]

Thanks for the replies. Packing redone many times.

 

[windyhill]

My 04 kx 250 was doing the same thing, after I had leaned all the carb circuits as well. About a month ago I went from a stock 50 to a 45 powerjet and so far the result looks good. I have'nt ridden a whole lot , but on my small track no spooge and much less smoke. I'm running a 42 pilot, 45 powerjet, NAFG needle and a 162 main all at 40:1 Just something to think about. JT

 

[Big Bore Stroker]

One quick check would be the float height. Chech this before making jetting changes.

 

[Aftermath]

How would that effect richness/leaness?

 

[gunr]

ha, mine to........... so far i have new pipe, new silencer, new clutch & new basket, new crank, bearings, rod(+ 3 mm stroker kit), new piston and rings, porting & milling the head for midrange & match to pipe.

used bike i bought for $1300 she ran great but pooped all over my new swing arm graphic. now she screams like a kamikaze and poops all over my ugly stained swing arm graphic.

i aint changin no jettin.

 

[Big Bore Stroker]

How would that effect richness/leaness?

If the fuel level is too low the engine will be fuel-starved under acceleration, in sharp turns and at full throttle. If the level is too high the engine will get flooded, run too rich or not respond to adjustments. Fuel in the carburetor must be maintained at a certain level under all operating conditions; this is the function of the float circuit. Everything starts with fuel level in the bowl.

 

[skipn8r]

I've changed to a leaner needle @ (2nd Clip), 42 Pilot and a 168 Main. Air screw out at 1.5 turns. as you can see, everything is leaned out

Which needle are you running?

 

[Aftermath]

Its one leaner than stock. I've even gone top clip which made zero difference. Regarding float height, I did have the reverse at one time where the bike was getting starved of fuel after long periods of wide open throttle (ps the bike still ran rich during this period). Float height is spot on, so it's not that. One thing no one ever mentions is the power jet. Not the pilot or main, but the power jet. This is still stock #50. Could this be the culprit...I wish I could sort this out

 

[Rcannon]

Try the 48 pilot. At 5000ft and 80 degrees I use a 45.

When the temp drops a 48 is good.

 

[Aftermath]

Already got 42 pilot....see first post in this thread. I'm talking about the power jet.

 

[Rcannon]

My error. Sorry. I saw pilot jet.....

I cannot help but think something else is wrong. I had the 45 pilot in my bike today. Again, altitude is 5000ft. Temp is about 70 degrees.

The bike would hardly start and was very lean. I HAD to up the size to a 48 and woudl have been able to use the stock 50.

What else have we missed. There HAS to be something. My bike is an 06 but our engines are identical.

If I tried a 168 main I would sieze my bike.

What fuel and oil are you using??? What ratio?

 

[BSWIFT]

If I tried a 168 main I would sieze my bike.

Why do you say this? Are your plug readings indicating a lean condition? Jet size numbers are a reference point. The plug reading tells you if you are rich or lean. My 05 ran real rich, lots of spooge, fouled plugs. I droped 2 sizes on the pilot and the main and I'm spot on. Elevation, 700'. A friend has the same bike, and is running stock jets and is running clean. Your engine will run what it needs not what numbers are ideal.

 

[Rcannon]

I said I would sieze at 168 because my plug indicates the bike runs well with a 172. I would probably not sieze, but a 168 would be too small. The 06 comes stock with a 178 mj. The 168 is 4 sizes leaner.