KTM 250 exc 2017 Keihin jetting

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1/14/2020 10:04 PM

Scratching my head with this one... I swapped out the Mikuni that came standard and inserted Keihin 38 PWK. Fitted a JD jetting kit and have arrived at : blue needle on 3rd clip, main 172, pilot 45, a/s 1 1/2.... running Klotz R50 at 60:1 with 95 octane. I have gone the rich pilot in an attempt to cure pipebang / deceleration chug.... better but not cured..... looking to clean up decel and have the power smooth to perky top end.... ageing bush bandit on weekend forest jaunts..... any help gladly excepted

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1/16/2020 11:57 AM

Steve, email James Dean at JD. He might ask about elevation and weather, but can probably give you some great tips based on the little info you have here.

If there are a lot of hours on the bike, replacing the silencer packing, having the exhaust seal at the header, fresh filter and top-end, stock cylinder head are all important.

Lots of guys throw performance mods at their buggered used bikes and wonder why it doesn't work out.

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KTM250SX YZ125 YZ85 PW80 ZX6 FZX700

1/16/2020 12:32 PM

Cheers mate , I will give him a ring. I bought the bike new and it has done less than 20 hours. I changed the Mikuni carb with a new Keihin and JD kit, but struggling with this pipe bang/ decel issue.... hoping it can be sorted with jetting rather than head work.

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1/16/2020 1:22 PM

Did that bike have a 36mm carb stock?

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1/16/2020 1:46 PM

A Mikuni TMX 38 is standard

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1/16/2020 2:02 PM

steve7 wrote:

A Mikuni TMX 38 is standard

👍

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1/18/2020 1:11 AM

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1/20/2020 10:35 AM
Edited Date/Time: 1/20/2020 10:38 AM

steve7 wrote:

Scratching my head with this one... I swapped out the Mikuni that came standard and inserted Keihin 38 PWK. Fitted a JD jetting kit and have arrived at : blue needle on 3rd clip, main 172, pilot 45, a/s 1 1/2.... running Klotz R50 at 60:1 with 95 octane. I have gone the rich pilot in an attempt to cure pipebang / deceleration chug.... better but not cured..... looking to clean up decel and have the power smooth to perky top end.... ageing bush bandit on weekend forest jaunts..... any help gladly excepted

There is a lot of info under the jetting section of the ktmtalk forum. Check out that and contact JD.

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KTM250SX YZ125 YZ85 PW80 ZX6 FZX700