KTM 2 stroke Sand Jetting

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5/22/2018 8:04 PM

Why in my manual does it say to jet it specific for riding in sand? I know that sand is hard on bikes but what exactly is it hard on? it says to throw in a super rich main jet a 470? just curious i never ride sand so i don’t know

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5/22/2018 10:23 PM

Engine is under more load.

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-'09 KX500AF

- '19 KX450F

5/23/2018 12:39 AM

Wide open for a lot more plus it's loaded so a lot of heat. Need to cool it down with richer jetting.

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5/23/2018 1:19 AM

UPSman334 wrote:

Why in my manual does it say to jet it specific for riding in sand? I know that sand is hard on bikes but what exactly is it hard on? it says to throw in a super rich main jet a 470? just curious i never ride sand so i don’t know

Which model year is it? I had a 2010 150sx with Keihin carb. Standard was something like a 165 Main Jet. The manual also said "use a 470 Jet for deep sand" which is clearly a typo or left over from a Mikuni carb.
I'd suggest you just run a main jet one size larger in deep sand than your normal setting for the specific sea level / temperature. A slightly richer mixture lets the engine run cooler and reduces the chance of pinging.

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5/23/2018 1:27 AM

Older generation 150SX will "ping" (detonation) itself to death with stock jetting in heavy sand. I have used #200 main jet in my 2013 150SX and I heard some guys running even bigger main jets in their 150's

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5/23/2018 2:02 AM

JMX82 wrote:

Older generation 150SX will "ping" (detonation) itself to death with stock jetting in heavy sand. I have used #200 main jet in my 2013 150SX and I heard some guys running even bigger main jets in their 150's

True, the top of my 150's piston looked like lava on the outlet side..

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5/23/2018 6:02 AM
Edited Date/Time: 5/23/2018 6:02 AM

#434 wrote:

Which model year is it? I had a 2010 150sx with Keihin carb. Standard was something like a 165 Main Jet. The manual also said "use a 470 Jet for deep sand" which is clearly a typo or left over from a Mikuni carb.
I'd suggest you just run a main jet one size larger in deep sand than your normal setting for the specific sea level / temperature. A slightly richer mixture lets the engine run cooler and reduces the chance of pinging.

Not a typo, with C12 I run a 470 MJ. With oxygenated fuel I'm running now I have a 490 in it.

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2018 KTM 250sx
Instagram CamaroAJ

5/23/2018 6:13 AM

UPSman334 wrote:

Why in my manual does it say to jet it specific for riding in sand? I know that sand is hard on bikes but what exactly is it hard on? it says to throw in a super rich main jet a 470? just curious i never ride sand so i don’t know

#434 wrote:

Which model year is it? I had a 2010 150sx with Keihin carb. Standard was something like a 165 Main Jet. The manual also said "use a 470 Jet for deep sand" which is clearly a typo or left over from a Mikuni carb.
I'd suggest you just run a main jet one size larger in deep sand than your normal setting for the specific sea level / temperature. A slightly richer mixture lets the engine run cooler and reduces the chance of pinging.

AJ565 wrote:

Not a typo, with C12 I run a 470 MJ. With oxygenated fuel I'm running now I have a 490 in it.

You should re read his post

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5/23/2018 6:17 AM

Fatten her up or blow her up wink

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