Honda XR250 1998 - Higher Revving Puff Of Smoke

Hey guys was just wondering about a small problem i have found out with my bike yesterday. I went for quite a long ride with a riding sa group and most of the roads were either 80km/h or 100km/h. Well i had regeared my bike from the previous owners 13/39 gearing to 14/48 and that gave me a top speed of about 120km/h instead of 140km/h. Well heres the thing because some of the roads were 100km/h the bike did have to rev rather hard for short - medium term periods and one of my fellow riders behind me said the bike did great except when decelerating after a medium term stint at 100km/h where it would blow out a puff of smoke. Is this normal for a XR250 since they are meant to be a lower revving bike and it is just some oil blow by? Probably due to the higher revs and hotter oil which might have been bubbling? Would this also be a sign of the rings/etc are slightly worn and the higher revs allow the oil to pass by or? Info as im not the best with bikes / I highly doubt it needs a rebuild etc but what would others do at 7500kms?. by the way it had new oil in it.

It wont happen again as i am going to put the old sprockets back on since i may need to cruise at 100-110km/h again and would rather do it comfortably. Also something i noticed about a month ago was a new noise which was coming from the engine. It sort of sounds like a rattle but only occurs now and then? I would almost think it could be the timing chain but this bike only has 7500km/h on it? When i pull in the clutch whilst going along it stops and when in 6th gear it stops but usually when decelerating is when i can hear it most and maybe whilst accelerating in the lower gears? If so is it a big job to replace or whats involved? The sound was more frequent yesterday in the lower gears to by the way.

Any info much appreciated.


what color was the smoke?

what color was the smoke?

I am unsure but the rider behind made it sound like burnt oil smoke but i am not totally 100% sure, what different types of smoke are there? Or are you thinking since it was revving higher that excess fuel had built up during this period and then when i started decelerating it ignited the build up and presto petrol smoke?. It cant of been too bad as he said he only saw a little puff on deceleration and the bike didn't smoke at all at any other time only on deceleration.

Any ideas then? (Also i started it up this morning to see if i could hear that weird sorta of noise which i am still awaiting feedback on which i think may be the timing chain but there was no sound of it this morning?)

Thanks for any help


Oil burning would be blueish. Incomplete burnt fuel is usually black. Raw unburnt fuel is white but seeing your bike has only one cylinder we know its now raw fuel because the engine wouldn't run.

I would do a compression test on the engine as well as a leak down test. If it puffs a little blue smoke on decel I would say the valve seals could be leaking a bit.

As far as he noise it could be the timing chain or valve adjustment. The thing is you said its not a constant noise but intermittent. I would check your kick starter. My wife bike was doing that after I had the engine apart. I thought my timing chain was out of adjustment but it was my kick starter was one spline off the shaft. I guess I put it back together wrong. My leg would rub the kick starter and it would make a strange noise. Engage your kick starter while the engine is running and you'll here the noise it makes.

A puff of blue/white smoke when opening the throttle after a deceleration from high engine revs indicates worn valve stem seals. On deceleration, the high intake manifold vacuum will cause oil to be pulled past worn seals and when you open the throttle, the small amount of oil is burned producing the smoke puff.


Hey guys i have an update and thank you for all the posts so far and please keep them coming.

Here is the reply from the rider who was situated behind me most of day that mentioned the smoke;


Hey guys was just wondering if the rider who was behind me on Sundays ride who mentioned the smoke on deceleration coming from my whittle Honda XR250R 1998 happened to have any more info on the puff of smoke on deceleration and what colour it was? Eg.

Did it look like blueish smoke indicating burnt oil?

Did it look like black smoke indicating incomplete burnt fuel?

Or did it sort of look like white smoke indicating raw fuel?

Sorry that i cant remember your name but you had the new bike you were still running in and it was 750cc something and looked sweet.

Please pm me if possible as i have asked on an XR forum and am trying to pinpoint the smoke on deceleration and any info/help you could provide would be much appreciated.




Yeah it was me , It was white colored smoke, It happened when you started to slow down eg going down to 80km from 100km outside Delamere, not sure if it was doing under acceleration or not, probably lasted for about 5- 10 secs maybe a little longer, then cleared, when it was idling it seemed ok.

I only saw it a couple of times, cause all the other times you were already stopped.

Hope that helps.

N3uRoTiC (Glenn)

Hope this little bit of info helps and what would white smoke indicate something real bad or something minor because above kc_450_X indicated that it was raw unburnt fuel but i didn't quite understand this statement;

"Raw unburnt fuel is white but seeing your bike has only one cylinder we know its now raw fuel because the engine wouldn't run."

Any help on this issue now with the updated information would be much appreciated and if its normal or if its a minor or major problem and what is involved fixing it etc.



It might run but very poorly if it did. White smoke could mean burning coolant ( does not apply with the 250) Over fueling or cold and not at proper operating temp. If you pull the spark plug and its golden brown your good.

If it only happened a couple times and was not alot of smoke I wouldn't sweat it. If your concerned about your engine you can always do a compression test and a leak down test.

My 450x is a 2006 with low hours and it smokes a little on start up... no worries just ride it.

It might run but very poorly if it did. White smoke could mean burning coolant ( does not apply with the 250) Over fueling or cold and not at proper operating temp. If you pull the spark plug and its golden brown your good.

If it only happened a couple times and was not alot of smoke I wouldn't sweat it. If your concerned about your engine you can always do a compression test and a leak down test.

My 450x is a 2006 with low hours and it smokes a little on start up... no worries just ride it.

So with the latest info i provided you reckon its just one of those little fussy picky things and nothing to really worry about? Also in order to do a compression test how do i go about it with the spark plug in the position it is in the XR250? And what sort of psi/pressure should there be for a Honda XR250 1998 with 7500km's? And i presume if its low it indicates that air/pressure is getting past the seals which is bad and if its normal/high that indicates no air/pressure getting past the seals etc which is good?

Last of all just want confirmation what causes the white coloured smoke? As does that mean its not burnt oil type smoke since its not blueish? And if not what caused it, just a build up of raw fuel then igniting at the end of a long revving stint? The reason i ask is that the bike seemed to be running like a dream even if it was revving harder then usual? Not rough like you are indicating it should if there is white smoke?

Any more info on this matter and confirmation?

Once again thank you very much guys.

Gas shall be in order.


If it runs good and doesnt miss keep running it, just keep an eye on the oil level.

Shes an older bike and if it aint broke don't fix it :thumbsup:

If it runs good and doesnt miss keep running it, just keep an eye on the oil level.

Shes an older bike and if it aint broke don't fix it :thumbsup:

Yer i hear what your saying. She is a good old trustworthy bike but i just don't want it to suddenly go bang for some simple reason and cost me a fortune eg. the timing chain. By the way does anyone happen to know what the compression should be on a Honda XR250R 1998 with about 7500km's?

Thanks again guys


Not sure about the compression. Could cal the dealer or I'm sure someone here would know.

If it idle's smooth doesn't miss on high throttle its probably nothing. Check the oil level like Britincali stated and you should be fine.

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