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Author Topic: Kx250 smoking when hot?  (Read 11161 times)

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Offline Shane3004

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Kx250 smoking when hot?
« on: January 12, 2014, 10:32:09 AM »
Wel lads was out on my kx 2day and noticed dat when i was in the forest, goin slow around trees and gettin stuck here and there the bike got a bit smokey, and when i get bak to the road and drive it on it spluttes a bit and clears its self out, It starts fine and runs wel on the roads, no smoke, just when i slow down, it has a fresh rebuild, jetting seems good, and the mix is 32:1, i think its a build up of oil when i go slow, what yous think? Thanks
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Offline sandblaster

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Re: Kx250 smoking when hot?
« Reply #1 on: January 12, 2014, 12:48:54 PM »
I think if you pull the spark plug you should know.
When you rebuilt it did you go larger on the bore?
What year is your bike and what is the jetting?
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Offline Shane3004

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Re: Kx250 smoking when hot?
« Reply #2 on: January 12, 2014, 10:03:15 PM »
Its a 96, standard bore, got the head replated, jeting is, slow jet 42, main jet 162 and needdle is second down from top, i tryed the neddle at 3rd down, but it wasent as snappy on the throttle, plug looks a bit oily and black, it has a full pc exhaust, im at sea level as well if dat makes a differents, it runs perfert and starts handy enough hot or cold?
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Offline dave916

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Re: Kx250 smoking when hot?
« Reply #3 on: January 12, 2014, 10:33:04 PM »
It could be burning gearbox oil/ right hand crank seal or case joint.
What sealer did u use on the cases?
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Offline Shane3004

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Re: Kx250 smoking when hot?
« Reply #4 on: January 13, 2014, 03:13:29 AM »
I doubt it cause theres new all balls racing bearings and seals gone in and i used black gasket sealer, it real gud, it about €40 tube here in ireland. And if it was dat it be a lot more smokey! I tink its not buring hot enough when driving easy, and causes a build up, im not sure wat to try doh!
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Offline sandblaster

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Re: Kx250 smoking when hot?
« Reply #5 on: January 13, 2014, 03:32:22 AM »
What air filter did you use?
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Offline Foxx4Beaver

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Re: Kx250 smoking when hot?
« Reply #6 on: January 13, 2014, 03:59:17 AM »
this might not have anything to do with it...but...how's the packing in the silencer?...if it's saturated with black spooge, then it wouldn't hurt to repack it.
I had a 250 that suddenly started smoking like a forest fire a few years ago....changed the saturated packing with some fresh new stuff, and it was all set. 

As the exhaust gets hot/hotter, all that black kucka starts to slowly burn/smolder, causing it to smoke excessively...worth a check :?
« Last Edit: January 13, 2014, 04:18:17 AM by Foxx4Beaver »
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Offline motopunk

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Re: Kx250 smoking when hot?
« Reply #7 on: January 13, 2014, 04:51:46 AM »
Quote from: Foxx4Beaver on January 13, 2014, 03:59:17 AM
this might not have anything to do with it...but...how's the packing in the silencer?...if it's saturated with black spooge, then it wouldn't hurt to repack it.
I had a 250 that suddenly started smoking like a forest fire a few years ago....changed the saturated packing with some fresh new stuff, and it was all set. 

As the exhaust gets hot/hotter, all that black kucka starts to slowly burn/smolder, causing it to smoke excessively...worth a check :?

i thought the same..old silencer-packing soaked with unburned 2stroke-oil.. repack the silencer and the smoking could be gone...
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Offline Shane3004

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Re: Kx250 smoking when hot?
« Reply #8 on: January 13, 2014, 08:26:48 AM »
Theres a twin airfilter in her, now dat u mention the exhaust packin, it is after gettin a bit louder lately, and after a spin the mud gaurd wud be a bit black from the exhaust, i,l try it doh and let ya,s no! Sound lads!
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Offline sandblaster

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Re: Kx250 smoking when hot?
« Reply #9 on: January 13, 2014, 08:46:50 AM »
Ok, two things.
Those two stage oil filters are easy to over oil which makes your bike run VERY rich.
Take the oil filter out and clean it and make sure you use a light coat of oil.
Then, pull your muffler apart and make sure that the packing is good.
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Offline don46

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Re: Kx250 smoking when hot?
« Reply #10 on: January 13, 2014, 10:26:03 AM »
based on what you said: going slow in the forest and when you lowered the clip it didn't run good I would say your jetting is to rich, pilot and/or needle. the good old idle screw will cover lots of jetting issues up, keep screwing in until it idles and usually when you first start it up it races for a bit = to rich down low.
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Offline hybridkdx

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Re: Kx250 smoking when hot?
« Reply #11 on: January 13, 2014, 11:37:16 AM »
While your at it, take the pipe off and get it real hot with a torch. Burn all the old oil out of it.
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Offline Shane3004

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Re: Kx250 smoking when hot?
« Reply #12 on: January 13, 2014, 08:28:53 PM »
Ya i soaked the filter in airfilter oil and rang it out and let it dry, but mite be to much, i clean it off and c how i go, the idle screw is broken cause it makes no differents, but like i said it starts grand, and doesent rev up when started, just a bit if the choke was on but dats normal, if i heat the header pipe wit gas torch wud it dis colour the exhaust? Is there any stuff i can pour in to soften the old 2stroke oil? One more question, can i buy jets single or do they come in a set? And if so were, and wud post world wide, kx parts are hard to get here! :x
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Offline dave916

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Re: Kx250 smoking when hot?
« Reply #13 on: January 13, 2014, 10:27:11 PM »
tt may be also worth checking the choke plunger [may be not fully closing dirt etc}
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Offline hybridkdx

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Re: Kx250 smoking when hot?
« Reply #14 on: January 14, 2014, 03:13:51 AM »
I have never had trouble with it turning them colors. Start with pointing the torch inside the pipe. There may be a couple flames jump out, but usually only an inch or so. You will see the oil burning out way before it gets hot enough to turn colors
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