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CRF 250r a little "smokey"

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i lso posed this in the general forum but I figured having it here might get more specific attention

So i bought a 2006 CRF 250r used the other day to add to my collection of toys at home. When i bought it everything seemed awesome, ive had bikes before so I knew mostly what to look for. Chain sprockets, suspension ect the obvious stuff.

When I bought it it didn't smoke a bit when you gave it a shot of throttle, hot, cold, or otherwise. Which seemed good, knowing that my buddy's 08 KTM which was freshly rebuilt even gives a small bluish whitish puff when its cold and gets a shot of gas.

Anyway i get the bike home, ride it for a few hours dropped it once, fairly gently, and took it home. However then after changing the oil i'm noticing that the bike smokes a bit cold and it goes away as it warms up, however it is still present.

I figure it is more than likely rings (although its supposedly on a rebuild less than 20 hours old and wasn't raced), or possibly valve seals.

i have a pretty good grasp on the inner workings of four stroke motors as I have rebuilt a few motors but I'd like to hear what you guys who are more familiar with dirtbikes suggest.

there is more smoke cold than warm.

only really started after the oil change (burning off the lighter components of the 10w40 i suppose)

I changed the air filter after it was dropped, it was dry on the outside (too dry) but a little oily on the inside

it still smokes some when warm

smoke is a light blue, and smells of oil, I know its not coolant.

thanks guys

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The valve guides on the exhaust valves are always suspect. It's a very common issue. I've seen the exhaust valves lose after as little as 40 hrs.

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yea thats what i was thinking.

i suppose intake guides could be an issue as well.

i took it for another ride yesterday and the amount of smoking seemed to vary. At one point i was in 5th at a constant speed and was just smoking constantly, however after that and a coold down, and topping up the oil (i had been out for a few hours and it went down the stick about a quarter) it was fairly smoke free except for when i punched it.

regardless i'm looking into a top end rebuild as parts worked out to around 250 dollars.

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yea thats what i was thinking.

i suppose intake guides could be an issue as well.

i took it for another ride yesterday and the amount of smoking seemed to vary. At one point i was in 5th at a constant speed and was just smoking constantly, however after that and a coold down, and topping up the oil (i had been out for a few hours and it went down the stick about a quarter) it was fairly smoke free except for when i punched it.

regardless i'm looking into a top end rebuild as parts worked out to around 250 dollars.

If it seemed to do it when you were beyond 3/4 throttle, you might want to take a look at what size main jet is in the carb. As many years as I've been wrenching on these things, I'm still questionable as to weather it's a oil control problem or a rich condition. There can be so many different variables that make it seem like it's one thing but turns out to be another. I'm just saying that before you start ripping the engine apart, take a look at the simple things first. I'm the first one that when a light bulb burns out on the car, I start looking for a bad module or looking for something way beyond the simple things first. Bites me everytime!

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yea i suppose.

although if it was a wrong sized main jet it would be running rich, giving me a gas smell in the fuel and a black cloud wouldnt you think?

Again im no expert either

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yea i suppose.

although if it was a wrong sized main jet it would be running rich, giving me a gas smell in the fuel and a black cloud wouldnt you think?

Again im no expert either

Sometimes, but understand that the 08/09 came stock with a 188/190 main in it depending on what part of the country or world you are in and it didn't huff black smoke. Even when you got into it there was very little smoke or rich symptoms besides being a dog on the top end. Opitimum set up for the 08/09 was a 172 or 175 main jet. That was the reason I asked about the main jet size. Not saying thats it, but easy stuff to check out first before jumping to conclusions.

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Sometimes, but understand that the 08/09 came stock with a 188/190 main in it depending on what part of the country or world you are in and it didn't huff black smoke. Even when you got into it there was very little smoke or rich symptoms besides being a dog on the top end. Opitimum set up for the 08/09 was a 172 or 175 main jet. That was the reason I asked about the main jet size. Not saying thats it, but easy stuff to check out first before jumping to conclusions.

yea that is for sure a good thing to check out.

i wouldnt assume jetting though. like its an 06, it runs mint, just burns oil.

and if it was a jetting problem making it run rich it may bog, flood, have starting issues and pitch a dab of black smoke.

thanks for the input though.

Have you changed a set of valve guides yourself before? i was looking into it and suggested procedure was freezing the new guides and heating the head then pressing the new ones in. then let the temperature even out and cool before reaming out the new guides.

i was sort of leaning towards taking it to the dealer for that part of the work

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yea that is for sure a good thing to check out.

i wouldnt assume jetting though. like its an 06, it runs mint, just burns oil.

and if it was a jetting problem making it run rich it may bog, flood, have starting issues and pitch a dab of black smoke.

thanks for the input though.

Have you changed a set of valve guides yourself before? i was looking into it and suggested procedure was freezing the new guides and heating the head then pressing the new ones in. then let the temperature even out and cool before reaming out the new guides.

i was sort of leaning towards taking it to the dealer for that part of the work

I know how, but don't have the right equipment to do it. If I did a ton of them, I'd invest in the tools. Find a local machine shop that does machine work on cars. Might want to make some phone calls first. The valve stems are 5mm so let them know that. They may not have the right size reamer for the guides. Chances are you'll have to provide them with the guides also. Should be somewhere around $25-$30 per guide give or take a little. That's for labor by the way.

Edited by Charlie C

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