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Discussion Starter #1
Hello,

When I accelerate my 2003 kfx 400 bluish smoke comes out from the exhaust. It looks like blue smoke but what can it be if it was white smoke also? My carburator was just cleaned and re-jetted a week ago and also the valves have been adjusted a week ago. It has a new ngk iridium cre7ix spark plug, new coil, and also has fmf titanium 4 exhaust and fmf powerbomb header, has the raptor petcock and I cancelled the vacuum line. Clean out the radiator and put in brand new anti-freeze. I want to know what is causing this color smoke if I recently serviced my valve adjustment, serviced my carb, new spark plug, and serviced my cooling system.

Please help me out because I don't want to blow my engine.

Thank You Very Much
 

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White smoke is usually coolant from a bad head gasket
blue is usually oil from bad rings
 

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Yes blue smoke is usually oil getting by the piston rings or valve seals.
What oil are you running? - the tolerances in these motors are so tiny that it pays to run at least Castrol or Valvoline formulated for wet clutch ATV/motorcyles.
Is the air filter cleaned regularly, and what filter are you using? - pull the air cleaner and inspect the inside of the airboot going into the carb. It should be squeeky clean, if its not the motor has been inhaling dirt which will cup the valves and wear or damage the cylinder/rings.
Has it been rolled upside down recently? - if its rolled over even for a few seconds oil can get into the little back breather box and tube that connects to the air intake. It will sometimes smoke some or quite a bit as this excess oil is pulled through the carb, but it should stop smoking after a while if there are no other problems.
 

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Discussion Starter #6
Yes blue smoke is usually oil getting by the piston rings or valve seals.
What oil are you running? - the tolerances in these motors are so tiny that it pays to run at least Castrol or Valvoline formulated for wet clutch ATV/motorcyles.
Is the air filter cleaned regularly, and what filter are you using? - pull the air cleaner and inspect the inside of the airboot going into the carb. It should be squeeky clean, if its not the motor has been inhaling dirt which will cup the valves and wear or damage the cylinder/rings.
Has it been rolled upside down recently? - if its rolled over even for a few seconds oil can get into the little back breather box and tube that connects to the air intake. It will sometimes smoke some or quite a bit as this excess oil is pulled through the carb, but it should stop smoking after a while if there are no other problems.
well the valves are brand new and were put in a couple of months ago but were re-adjusted to its correct specs a week ago...its using valvoline 10w-40 full synthetic with wet cluth protection...it has a brand new uni-filter on it since i go dune riding a lot...the carb and the boot were cleaned and re-jetted also a week ago...please help me out
 

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Good post by sandman74, lots of good ideas there.
When did the smoking start? Why did you install new valves?
130 isn't bad for a 400.
Oil burning can come from two sources; worn piston rings (or at least a bad oil ring), or valve seals.
Valve seals usually cause smoke at start-up; the oil rins down past the seal after you shut the engine off, and then gives a puff of smoke when you restart it. If a valve seal pops off completely, then you may get smoke as you accelerate.
Smoking under load usually means worn/weak rings. The compression rings may still be in tolerance, but the oil ring could be weak.
It won't blow up, you could probably drive it for years.
Is it actually taking oil?
 

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Discussion Starter #10
Good post by sandman74, lots of good ideas there.
When did the smoking start? Why did you install new valves?
130 isn't bad for a 400.
Oil burning can come from two sources; worn piston rings (or at least a bad oil ring), or valve seals.
Valve seals usually cause smoke at start-up; the oil rins down past the seal after you shut the engine off, and then gives a puff of smoke when you restart it. If a valve seal pops off completely, then you may get smoke as you accelerate.
Smoking under load usually means worn/weak rings. The compression rings may still be in tolerance, but the oil ring could be weak.
It won't blow up, you could probably drive it for years.
Is it actually taking oil?
Well my father in law is the one who put the valves brand new i bought this quad off from him about 2 months ago and ive done all the tunes ups and everything it says that i have done to it in the last posts...the smoking has been there from the day i bought it and a week ago the valves were regulated because the exhaust valve was too tight it wasn't letting all the exhaust to come out. ive noticed smoke comes out when its on neutral and i rev all the way and let it go then smoke comes out...what should be a good compression number???
 

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All the info you need is posted above.
You can have good compression but still burn oil.
It needs new rings, or a top end rebuild. Or you could just drive it the way it is.
BTW, if the valve lash was set loose enough that the engine couldn't get rid of the exhaust, then the engine must have been HORRIBLY noisy.
 

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Discussion Starter #12
All the info you need is posted above.
You can have good compression but still burn oil.
It needs new rings, or a top end rebuild. Or you could just drive it the way it is.
BTW, if the valve lash was set loose enough that the engine couldn't get rid of the exhaust, then the engine must have been HORRIBLY noisy.
ook thanks for all the info im very grateful :)
 

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If the smoking gets noticably worse and it starts to use/burn a lot of oil. (i.e. if it starts puffing oil like a 2 stroke, its definitely time for a full top end overhaul)
 

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Discussion Starter #16
If the smoking gets noticably worse and it starts to use/burn a lot of oil. (i.e. if it starts puffing oil like a 2 stroke, its definitely time for a full top end overhaul)
ill keep an eye on that and if it does do that then ill make those changes to my engine
 
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