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2009 KX250F Motor Problems.. or Something?

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Although most people I tell, seem to find this hard to believe.. I bought a 2009 Kawasaki KX250F the other night. I got it for $2,300 :banana:, with the knowledge that it could possibly have some motor problems. The owner had an hour meter on the bike, 10 hours total, but the motor was a complete rebuild. The Cylinder, Piston, Rings and Clutch was all replaced. He said the clutch seemed to disintegrate into peices, and tore up everything he replaced. He said he took the motor apart and cleaned out all the shavings and had a mechanic put in all the new parts and everything. After putting the bike back together, he had the same bike, and said the one I bought seemed to be circulating oil slower in the sight glass than the other, which I don't know how you can tell through a sight glass.. so he didn't ride it or let it run.

Now here's my part. I took the bike home and decided to start it up and let it run for a little bit to see what it was doing. The bike didn't start when I got it home, it had a fouled plug so I changed it out real quick, put a BR8 in it, stock plug. I start it up on the first kick, ran great, sound's great but after a minute or so I turned off the choke and it started back firing, was bogging down terribly, and started shooting a monster flame out of the pipe. I put the bike in gear and rode it up and down the street for a minute, and it continued to backfire and bog down, still shooting flames out the exhaust, so I decided I would turn it off and let it just sit. When I hopped off, I looked down and there was some coolant pouring out of the over-flow. I don't know why, I had the right amount in it, but I felt the radiator and it was HOT. The casing/side of the motor was also very warm.

I've pretty much gave you all the information I have about the bike, I will probably take it to a mechanic and have it ripped apart, but I thought I would post this on here and see if I could get a few idea's on what could be wrong with it.

Again.. It runs, and rides great, has a new piston, rings, cylinder and clutch, so i'm clue-less!

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Sounds like either the pilot jet is clogged or it is jetted too lean. I would try giving the carb a good cleaning and see if that fixes it. Also check the hot start plunger to make sure it isn't sticking open.

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ForsheeMS is right.

A lean running engine will pop and rise in temperature.

Clean the carb, make sure you have a #42 pilot jet, check that hotstart closes completely and inspect that there is no header leak.

Drain the oil and fill with 1 liter (1 quart).

Clean air filter and inspect everything in the airbox and intake.

Then run it again and see how it feels. Also, it´s normal for the bike to boil over if idled for a couple of minutes.

Btw, check that the radiator caps gaskets are clean and free from mud and that the filler neck is perfectly round.

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I've completely cleaned out my carb, checked for leaks, checked for the hot start to be sticking open, cleaned the bike inside and out, it's still doing the same thing, tried different spark plugs. It's a mystery to me, I cleaned my oil ports and screens in the motor, and still have poor circulation in the motor. I'm completely lost on what the deal is. Going to take it to a real mechanic sunday and see if they can see what the deal is.

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I've completely cleaned out my carb, checked for leaks, checked for the hot start to be sticking open, cleaned the bike inside and out, it's still doing the same thing, tried different spark plugs. It's a mystery to me, I cleaned my oil ports and screens in the motor, and still have poor circulation in the motor. I'm completely lost on what the deal is. Going to take it to a real mechanic sunday and see if they can see what the deal is.

I´m curious, how did you measure the rate of circulation?

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Well lack of oil circulation. Will not cause back fire. This is a jetting issue.

As far as lack of oil flow. This could be due to clogged oil passages. If the clutch did disintergrate and the person who rebuild it did not fully clean the passages it could have foriegn contamanites clogging the oil passages.

How ever letting the bike sit and idle on a stand it will only take about 30-60 seconds to heat up and only about another minute if that to over heat.

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Like I said man, I didn't look into the oil circulation, the guy that had it before me had 3 other bikes (09 kx250's) and he said this one through the sight glass didn't circulate as well as the others.

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The oil you see through the sight glass is being "circulated" by the clutch and is in no way an indication of the how much oil is being moved by the oil pump. That being said, the 2009 Kawi's seize the intake cam when the oil pressure drops for any reason. If you had oil pressure issues it would have probably locked up by now.

The popping you are describing is normally caused by lean jetting, a stuck hot start plunger, or an air leak (could be intake or exhaust). You said you have cleaned the carb but did you remove all the jets and thoroughly inspect/clean them?

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