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'99 KX250 Smoking a bunch more all of a sudden

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Did a top and bottom end on my bike a few weeks ago. After a couple of heat cycles I put a solid 4 hr. ride on it 2 weeks ago with no problems. It rode great. Getting ready to ride this weekend so did a bit of maintenance. Only thing I did motor wise was setting the float level.

Went out to kick it over this afternoon and buzz around the block. Without winding it out at all, I noticed as I'd cut the throttle it would smoke out the silencer for a second. Put it in the garage and a couple of hours later figured I'd let it run for 10-15 minutes and see if it would clear up after the bike warmed up. It didn't.

Kicking it over it fires no problem and idles just fine. Only thing is there is a little smoke rolling out the silencer as it idles. Again if I grabbed some throttle and let off, a decent puff of smoke would roll out after letting off the throttle.

Kind of at a loss as I wouldn't think it has lost a crank seal with only about 5 hrs. on the motor. After letting it run and then cool, I checked the coolant level (50/50) and it hasn't lost any coolant.The only thing I did to the fuel system is lower the float level to the correct level (7.12mm). As far as I can tell, the trans oil level hasn't lowered.

Any thoughts?

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drain the carb and put some fresh mix in it. Maybe the lower float level was messing with some residual oil in the carb? Causing it to smoke more?

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things that can cause a change in the amount of smoke- a new plug/ differnet oil mix as well as the ratio it is mixed/ the oct. level on the gas/ and the tuning on the carb. i had a 1999 gas gas ec 250 at one time and i noticed when i swaped out the plug to a NGK iridum and started running motul, the bike didnt smoke as much, which was kinda a bad thing cause the less oil u have in the mixture the higher the percentage is to burning up ur top end and doing damage to the crank. the extra smoke isnt a bad unless ur feeling a lack of power in the bike.

Edited by Sebastian Pavich

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The power (didn't go past 1/2 throttle ) still seemed fine, just excessively smokey.

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Any thoughts if it could be the float? I set it by flipping it upside down at about a 45 degree angle so the float wasn't pushing on the plunger and measured the height from the bowl mounting surface to the bottom of the float with a digital caliper.

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If the fuel level was low b4 you set the float and it was jetted to suit that, it could be running rich now. Have you checked the jetting sinced you changed the float?

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Re-checked the float and tried dropping the pilot a step today just to see if it would help and ran it for another 10-15 minutes. It didn't. It did the same thing but now when at idle it didn't really smoke. As soon as it was off idle it would smoke and again if I wound it up and let off it would roll a puff of smoke out the silencer before settling back down. I thought it might be a coolant leak as I smelled a hint of coolant but again after it cooled the radiator was at the same level and there was no sign of oil mixing with it.

Tried smelling around the silencer and didn't smell coolant or ATF (in the trans).

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I'm leaning towards a fuel issue. I've been into the carb a couple more times and everything checks out. This morning I dropped the float height a couple of MMs and tried again. Same outcome. It seems to be using a bunch of fuel (clear tank) but I can't figure out what's off.

Took a quick vid of what it's doing.

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Sprayed some soapy water at the trans. vent. Got a very slow forming bubble about 1/2"in size. I'm guessing this means the crank seals are still alright. :busted:

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if it was a there was a cracked radiator jack in the head then the color of the smoke would be a wierd non gray color. and yet again the level of radiator fliud would be low.

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Ha, are you letting the bike idle for 10-15 minutes also, and its SMOKING, a bloody 2 stroke? Oh no, good luck fixing that problem lol.

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If your worried do a pressure test to check the seals for sure, there is a thread on it in the FAQ stickey above.

Ed

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If u look in a kawasaki kx250 manual it tells u that if you see soap air bubbles coming out of the crankcase vent while pressurized then your right crank seal is leaking & both seals must be replaced immediately before next start up.

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It's normal, infact, run more mix to lube the piston. You'll loose some horses, but it's better to save the motor than risk a few hundred bucks. If it isn't the mix, and it is seals/gaskets, then good luck with the rebuild. My bike isn't a power-valve model so it smokes unbelievably. Not to mention I run a 32:1 ratio.

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