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Ktm150sx goin through plugs like crazy

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Are you riding the bike hard or do you putt around on it?

 

Bike is probably too rich.  Do you know what your jetting is or is the jetting stock?

 

Have you tried any other ratios of mix?

 

What type of oil?

 

Is the spark plug the one the bike recommends?

 

What do they look like afterwards (dark?)

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Is this a recent occurence? Did it always do this, or did it use to run fine and has just started fouling plugs suddenly?

 

If it's always done it, it's probably a jetting issue.

 

If it's a recent change, it's a mechanical issue, such as worn/chipped/cracked reeds or a leaking tranny-side crank seal.

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DirtSmoker250 is right on the money.  The bike is running too rich which is a jetting problem.  For a 150cc two-stroke I would mix at 32:1 with a good quality oil.  There are lots of good two-stroke oils on the market.  Maxima, Amsoil and Motul are all good quality oil brands.  Of course there are several others as well.  A properly jetted two-stroke can definitely be ridden for hours at low RPMs without fouling the spark plug.  Sometimes I ride my two-strokes at very low RPMs on tight trails for hours and never get out of second gear; without fouling the spark plug.  I had to go down three sizes on my main and pilot jets both in my 2007 YZ250 before I started seeing a nice, tan/mocha colored spark plug when I got a reading on it.  I also swapped out the stock needle and made a clip adjustment as well on that bike.  Another thing I did was switch from Yamalube 2R oil to Amsoil Interceptor.  With the two-strokes it's mostly about jetting.  Just pick a ratio to jet for, such as 32:1, and begin making your incremental changes.  I'm sure that someone on this forum that owns a KTM 150SX can make some baseline recommendations for you if they ride at places where the average temperature and elevation is very similar to your riding conditions.  If you are riding MX tracks at extremely high RPMs then you don't want your jetting to be as lean as if you are riding trails at low RPMs the vast majority of the time.  Please keep in mind that less oil is actually a richer condition.  This is the exact opposite of what most people think.  Less oil means more fuel so the bike will be running richer.  More oil leads to higher combustion chamber temperatures.  Like Chokey said, if this spark plug fouling issue has just recently started then it is another type of mechanical issue.

Edited by ron_m
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DirtSmoker250 is right on the money.  The bike is running too rich which is a jetting problem.  For a 150cc two-stroke I would mix at 32:1 with a good quality oil.  There are lots of good two-stroke oils on the market.  Maxima, Amsoil and Motul are all good quality oil brands.  Of course there are several others as well.  A properly jetted two-stroke can definitely be ridden for hours at low RPMs without fouling the spark plug.  Sometimes I ride my two-strokes at very low RPMs on tight trails for hours and never get out of second gear; without fouling the spark plug.  I had to go down three sizes on my main and pilot jets both in my 2007 YZ250 before I started seeing a nice, tan/mocha colored spark plug when I got a reading on it.  I also swapped out the stock needle and made a clip adjustment as well on that bike.  Another thing I did was switch from Yamalube 2R oil to Amsoil Interceptor.  With the two-strokes it's mostly about jetting.  Just pick a ratio to jet for, such as 32:1, and begin making your incremental changes.  I'm sure that someone on this forum that owns a KTM 150SX can make some baseline recommendations for you if they ride at places where the average temperature and elevation is very similar to your riding conditions.  If you are riding MX tracks at extremely high RPMs then you don't want your jetting to be as lean as if you are riding trails at low RPMs the vast majority of the time.  Please keep in mind that less oil is actually a richer condition.  This is the exact opposite of what most people think.  Less oil means more fuel so the bike will be running richer.  More oil leads to higher combustion chamber temperatures.  Like Chokey said, if this spark plug fouling issue has just recently started then it is another type of mechanical issue.

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Is this a recent occurence? Did it always do this, or did it use to run fine and has just started fouling plugs suddenly?

 

If it's always done it, it's probably a jetting issue.

 

If it's a recent change, it's a mechanical issue, such as worn/chipped/cracked reeds or a leaking tranny-side crank seal.

I'm with chokey on this one i had a right side crank seal leak that was actually the collar the seal rides on worn a groove . If it just suddenly started i'd give that a look and it's a simple fix. Will soak a plug in minutes .

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I just got the bike. 40:1 works great! Ima stick to that and make everything work with that. I'm not FOULING the plug cause it isn't oily. I feel like I'm just burning through plugs with te high rpms. The plug looks like a mocha coffee where it ain't burnt white or it isn't oily black. It's just right in between. Idk but I have I change the plug every track day

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Could be reeds, or just jetting, or a right side crank seal. All easy fixes. If you see your tranny fluid is low, replace that seal. Slavens racing and Cooksey crank makes an improved gasket for it. If not the gasket, I like JD jetting. I have had good luck with them. Super easy jetting, and believe that it is worth the money. If you have any more specific questions you can PM me. Edit: you could try a hotter plug, also. I saw that your plug isn't oily. Or it's reeds.

Keep 'Er Rippin

Biggins

Edited by -Biggins-

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It's honda hp2 two stroke oil full synthetic and yes right spark plug. 40:1 ratio

Bike isn't putted on. It's rode hard and gonna get ride harder an harder as I learn in since icane off a kx250f

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It's honda hp2 two stroke oil full synthetic and yes right spark plug. 40:1 ratioBike isn't putted on. It's rode hard and gonna get ride harder an harder as I learn in since icane off a kx250f

the oil dosent matter. You could try a colder plug also. At 3$ a plug, try one size colder, and one size hotter.

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My Ktm 150sx is going through plugs like crazy. 2010 model. 40:1 ratio. Any advice thanks

I run my son's 50sx and mine 250sx with the recommended mottel oil mixed at 60:1 I don't care what anybody tells you I tried richer mixtures and the bike ran hot a lived up to the name smoker...oil lubes and gas actually cools the engine ktm engineers are not putting 60:1 ratio in the manual to have every body to blow up there engines. Your bike is not going to blow up its going to run nice and crisp. All these guys are afraid to mix it that lean including myself and I ride on the pipe times two...my son's bike quit overheating, he's only five so he's not on the pipe all the time so his bike used to over heat until I changed the mixture.

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I run my son's 50sx and mine 250sx with the recommended mottel oil mixed at 60:1 I don't care what anybody tells you I tried richer mixtures and the bike ran hot a lived up to the name smoker...oil lubes and gas actually cools the engine ktm engineers are not putting 60:1 ratio in the manual to have every body to blow up there engines. Your bike is not going to blow up its going to run nice and crisp. All these guys are afraid to mix it that lean including myself and I ride on the pipe times two...my son's bike quit overheating, he's only five so he's not on the pipe all the time so his bike used to over heat until I changed the mixture.

I also run motorex at 60:1 in a 300xc. I trust the engineers. I lug sometimes, on the pipe sometimes, usually in between. Once the bike was jetted properly, it was perfect throughout the throttle. Sounds like the OP has a jetting issue
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I just got the bike. 40:1 works great! Ima stick to that and make everything work with that. I'm not FOULING the plug cause it isn't oily. I feel like I'm just burning through plugs with te high rpms. The plug looks like a mocha coffee where it ain't burnt white or it isn't oily black. It's just right in between. Idk but I have I change the plug every track day

 

 

What exactly is happening that makes you have to change the plug?

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But once you put a new plug in, it runs fine for that entire day? And you don't have any trouble until you try to start it the next time you go riding?

 

I'm thinking you have a weak coil, or a stator that's going bad. KTMs also used to have a resistor inside the spark plug cap that can go bad, but I don't know if they still do.

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