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HELP!! jetting is perfect but still runs rich

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So the other day i bought a brand new 2017 ktm 250sx

I took it for a ride on the mx track and it was great, heaps of power and good suspension. I took it home, cleaned it and did a little bit of maintenance. the next day I tried turning on the bike and it just didn't want to start. I thought it might of been a spark plug so I took it out and it was flooded with black stuff. It was a failed plug obviously. I did my research and it said if it's black, it's rich. so I changed the plug and it started right up with no problems. I checked the owners manual and it said main jet (440), idiling jet(42,5), needle(43-73), clip position(3), idle air screw(2 turns out) and my gas mixture is 50:1. it was all perfect for the temp and height I was riding at so i really dont know what's wrong. there is black oil coming from the exhaust aswell.

Could anyone please help me and sort this out.

cheers

Edited by Ben Causevic

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Sounds normal, you fouled a plug on a 2 stroke. Happens a lot. Carry extra plugs all the time or you will get stranded. 

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I kant help you with the Mikuni with specific advice. If the bike pulls nice on the top end and idles well I'd try dropping the needle a clip and see if it runs better.

Fouling plugs is only normal if it's not jetted cleanly. I could leave my spare plugs back at the car and not get stranded because of a fouled plug I guarantee it, and it's not because I ride on the pipe all the time.

I have used them on friend's bikes but never mine.

 

 

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9 hours ago, BushPig said:

I kant help you with the Mikuni with specific advice. If the bike pulls nice on the top end and idles well I'd try dropping the needle a clip and see if it runs better.

Fouling plugs is only normal if it's not jetted cleanly. I could leave my spare plugs back at the car and not get stranded because of a fouled plug I guarantee it, and it's not because I ride on the pipe all the time.

I have used them on friend's bikes but never mine.

 

 

thanks for the help I'll try dropping the clip and see what happens. I've also noticed that black oil is dropping out my exhaust, could that be a sign of something bad?

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Book jetting doesn't mean real world perfection, reference only it seems, especially on the 17s. Lots of 17 KTM jetting threads, you will get it dialed in.

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29 minutes ago, DEMI said:

Book jetting doesn't mean real world perfection, reference only it seems, especially on the 17s. Lots of 17 KTM jetting threads, you will get it dialed in.

Could you please link me some of these threads cause I can't really find them

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14 hours ago, Ben Causevic said:

owners manual and it said main jet (440), idiling jet(42,5), needle(43-73), clip position(3), idle air screw(2 turns out) and my gas mixture is 50:1. it was all perfect for the temp and height I was rising at so i really dont know what's wrong.

 

What kind of fuel are you using in that bike?  Different fuels require different jetting.  

Also, how are you riding the bike?  Lots of Wide Open Throttle?  Lots of high revving?  

If you answered "no", then thats the real problem!

How long do you let your bike idle before you put it in gear and start riding?

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10 minutes ago, Ben Causevic said:

Could you please link me some of these threads cause I can't really find them

 

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1 hour ago, Ben Causevic said:

thanks for the help I'll try dropping the clip and see what happens. I've also noticed that black oil is dropping out my exhaust, could that be a sign of something bad?

Black oil dripping from exhaust is normal on a two stroke.  I've never had a 2 stroke that did not drip oil from the exhaust.  And I VERY rarely foul spark plugs.  Always running Amsoil Dominator in the two strokes, as well.  Idc what the MFG recommends.  Amsoil Dominator is better.  

Also, regardless of what the MFG recommends, I run 32:1 oil/fuel ratio.  Even in my XC250.  I put about 120 hours on that XC250 in the woods and motocross tracks and I honestly don't recall ever changing the plug for any reason.  I never rejetted for changing seasons, or anything.  My jetting was ALWAYS WRONG, and I NEVER fouled a plug. 

Same exact story with my RM125, and the several YZ250 2 strokes I've owned.  32:1 + Amsoil Dominator + Wrong jetting (usually way too rich) = I never ever foul plugs on any bike.  So theres that. 

Edited by dirtjumpordie

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1 hour ago, DEMI said:

Book jetting doesn't mean real world perfection, reference only it seems, especially on the 17s. Lots of 17 KTM jetting threads, you will get it dialed in.

Exactly. 

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27 minutes ago, dirtjumpordie said:

Black oil dripping from exhaust is normal on a two stroke.  I've never had a 2 stroke that did not drip oil from the exhaust.  And I VERY rarely foul spark plugs.  Always running Amsoil Dominator in the two strokes, as well.  Idc what the MFG recommends.  Amsoil Dominator is better.  

Also, regardless of what the MFG recommends, I run 32:1 oil/fuel ratio.  Even in my XC250.  I put about 120 hours on that XC250 in the woods and motocross tracks and I honestly don't recall ever changing the plug for any reason.  I never rejetted for changing seasons, or anything.  My jetting was ALWAYS WRONG, and I NEVER fouled a plug. 

Same exact story with my RM125, and the several YZ250 2 strokes I've owned.  32:1 + Amsoil Dominator + Wrong jetting (usually way too rich) = I never ever foul plugs on any bike.  So theres that. 

black oil or spooge is NOT normal , it is a symtom of a rich mixture , excessive smoke is not normal either

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1 hour ago, kxrob said:

black oil or spooge is NOT normal , it is a symtom of a rich mixture , excessive smoke is not normal either

Well I've owned and seen many good running two strokes that have spooge coming from the exhaust.  If it were a problem, I would alraedy know about it.  Its fine. 

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