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Doh!...Blue Smoke

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If I give my bike a shot of gas while it's idling, I get a little puff of blue smoke from the exhaust. But not seeing any blue smoke under hard acceleration. And no blue smoke on start up on the choke when cold, or on warm start up without the choke, as long as I don't blip the throttle.

-The air filter isn't over oiled.

-I'm not over full on oil. I changed the oil and filter and refilled with the correct amount to make sure.

-No sign of oil on the exhaust valve stems when you look through the ports, so I'm pretty sure it's not the exhaust stem seals.

-I'm thinking of pulling the carb to get a look at the intake valve stems to look for oil on those, but haven't done that yet.

-The bike has fairly high hours but low mileage (2500 kms). Lots of slow speed bump and grind technical riding.

-Plug electrode colour looks spot on and is clean, but I do see a small amount of oil residue on the plug threads.

-Full FMF exhaust system, AIS removed, JD jetting kit, airbox opened up.

Looking for input on something simple I may not have thought of, before I tear down the top end.

Thanks in advance.

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I just bought my new '08 a month ago. It now has about 75 pretty easy fire-road miles on it. It has the same exact mods you listed, plus a Boyeson Accelerator pump cover. I also get a light puff of smoke when blipping the throttle when the engine is fully warm. So maybe nothing is wrong with your bike. There might just be a momentary rich condition due to the accelerator pump.

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I just bought my new '08 a month ago. It now has about 75 pretty easy fire-road miles on it. It has the same exact mods you listed, plus a Boyeson Accelerator pump cover. I also get a light puff of smoke when blipping the throttle when the engine is fully warm. So maybe nothing is wrong with your bike. There might just be a momentary rich condition due to the accelerator pump.

^ This

Since day one, I've always gotten a little puff here and there. I, like you originally thought something was wrong. 4yrs later, and well over 10K miles, trail and dual sport...I still get a puff :thumbsup:

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It may be something common with these bikes, as you guys have suggested, but it's not black smoke like you'd normally expect from a rich state, and it has only started doing it recently. It's definitely blue-ish/white oil smoke, that has that distinct oil smoke smell.

The bike starts easily hot or cold, and runs top-notch (pulls like a freight train), but I'd love to know how oil is reaching the combustion chamber in amounts great enough to cause the puffs of smoke when I blip the throttle. In my experience that usually means bad valve stem seals or blow-by getting past the rings.

Edited by DRZ400SK4

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It may be something common with these bikes, as you guys have suggested, but it's not black smoke like you'd normally expect from a rich state, and it has only started doing it recently. It's definitely blue-ish/white oil smoke, that has that distinct oil smoke smell.

The bike starts easily hot or cold, and runs top-notch (pulls like a freight train), but I'd love to know how oil is reaching the combustion chamber in amounts great enough to cause the puffs of smoke when I blip the throttle. In my experience that usually means bad valve stem seals or blow-by getting past the rings.

Time to ring it and do a valve job. If you don't ride WFO all the time it might go for years. It's all up to you man..

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The accelerator pump may be a little rich for your setup. It has an adjustment screw near the throttle linkage on the carb.

It's blue-ish/white oil smoke, not the black smoke you typically see from a rich state.

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It's blue-ish/white oil smoke, not the black smoke you typically see from a rich state.

Do you notice more smoke on your first start up after it has set overnight or longer?

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does your bike use oil? My old KX used to smoke a little when the piston and rings needed replaced. But it would also consume a noticeable amount of oil from the crankcase, requiring a top-off after a few hours of hard riding. If you aren't losing/using any oiil I would still suspect too rich on the accel pump. Color of smoke can be deceiving....

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Do you notice more smoke on your first start up after it has set overnight or longer?

Doesn't seem to matter...I can start it after it's sat for a week, and when I blip the throttle I get the puff of blue-ish oil smoke, or I can go for a ride, and when I return blip the throttle, and it will give me the same little puff of blue oil smoke. That's why I'm doubting that it's valve stem seals, because in that case you'd probably only notice it after the bike had sat for awhile. besides, bad valve stem seals at only 2500 kms would be unusual.

If you aren't losing/using any oiil I would still suspect too rich on the accel pump. Color of smoke can be deceiving....

If I'm using oil it's not much, but it's hard to tell, since I change the oil so often. But it's definitely oil smoke, and not smoke from a rich state of tune. Aside from the colour, you can smell burnt oil in the puffs of smoke. Unspent fuel smoke, caused by a rich state, has a definitive gasoline smell.

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Doesn't seem to matter...I can start it after it's sat for a week, and when I blip the throttle I get the puff of blue-ish oil smoke, or I can go for a ride, and when I return blip the throttle, and it will give me the same little puff of blue oil smoke. That's why I'm doubting that it's valve stem seals, because in that case you'd probably only notice it after the bike had sat for awhile. besides, bad valve stem seals at only 2500 kms would be unusual.

If I'm using oil it's not much, but it's hard to tell, since I change the oil so often. But it's definitely oil smoke, and not smoke from a rich state of tune. Aside from the colour, you can smell burnt oil in the puffs of smoke. Unspent fuel smoke, caused by a rich state, has a definitive gasoline smell.

Word. I think it maybe time to do a ring job. Do you still have the crank case vent hose going to the air box? If so pull it off plug the air box side and put a vent hose uni-filter on it and see if it still does it. A side from valve stem guides or seals. the crank case and rings are the only other causes white/blue smoke.

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I have 3500km on the klx and you can see the bit of smoke when you blip the throttle too

It has done that for as long as I can remember - who cares ! - I bought this thing to ride it

NOT polish it or work on it ! It hardly uses any oil so I ride it ! suggest you do the same

the only concern I have is the piston failing and causing a mess - not a bit of smoke !!

What life is the piston good for on the KLX ? :thumbsup:

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Word. I think it maybe time to do a ring job. Do you still have the crank case vent hose going to the air box? If so pull it off plug the air box side and put a vent hose uni-filter on it and see if it still does it. A side from valve stem guides or seals. the crank case and rings are the only other causes white/blue smoke.

If he needs rings...he's doing something else REALLY WRONG! I don't think that's the case. My rig after 10,000 miles didn't need rings and the hone looked great.

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If he needs rings...he's doing something else REALLY WRONG! I don't think that's the case. My rig after 10,000 miles didn't need rings and the hone looked great.

That's great news! What kind of riding do you do?

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That's great news! What kind of riding do you do?

Just about anything from trails to endurocross. I've motocrossed it a couple times, and it was an epic failure. Mostly due to setup...I run SOFT suspenders. I raced a couple weekends back at the RimrockGP which is a high speed blast in a lake bed. Try to ride singletrack a couple times a week, so the miles add up. Odometer broke last spring at the Sparkplug enduro when it went offtrail into a tree. I'm not sure how many miles are on it today. Starts one or two kicks warm or cold. Too bad it's a pig. :thumbsup:

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If he needs rings...he's doing something else REALLY WRONG! I don't think that's the case. My rig after 10,000 miles didn't need rings and the hone looked great.

I remember that post of yours with the pics. How else could he be burning oil ( blue white smoke) if the top end is solid. I would think it would be blow by and pulling it through the crank case breather. Just my thoughts.

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It's just one of those things I kinda need to experience firsthand to give an educated opinion, however from his basic description, I'm imagining him as myself shortly after getting my bike and pondering the 'puff'...nowadays, I just sorta know it exists.

I'm wondering if the break-in went well?

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Aside from the colour, you can smell burnt oil in the puffs of smoke.

The smell of burnt oil is a tell-tale sign. Based on your description of symptoms, I recommend a new piston and rings (wiseco or JE with coated skirts). Make sure you hone your cylinder with a traditional 3-stone hone. Some people believe that nik-a-sil bores don't need to be honed and this is FALSE. You need to remove the glaze from the bore and re-establish the cross-hatching before you install your new piston and rings. Do not use a ball-hone, use a 3-stone. 320 grit is good. Also be sure you are only using dino oil (not synthetic) for the break-in period so that the rings can wear in properly.

One other tip: do not replace the rings alone while re-using the original piston. I say this for a couple reasons. Mainly because the piston is the wear item in the cylinder/piston combo. The nikasil plated bore is very tough and it can wear out many pistons before it loses it's roundness. the second reason I recommend replacement is because the OEM piston is cast aluminum not forged like the wiseco or JE. Forged is much stronger and when a forged piston fails they dont disintegrate into a million pieces like cast pistons...making for a much easier repair if/when the time ever comes.

Cheers!

Edited by Johns08KLX450R

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