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Help For KTM 2007 EXC-F 250

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I've a 2007 KTM EXC-F 250.

There is fmf factory full system with powerbomb header on the bike.

The jets and the carb all are stock.

Here are the problems:

- Exhaust is popping too much at deceleration

- Bogging at low rpm

- Generally stalls at idle

- Sometimes doesn't start (generally when its hot)

I ride at sea level.

These are from the owners manual;

250 EXC-F

Keihin FCR-MX 3900G

Main Jet: 168

Jet Needle: OBEKT

Idling Jet:40

Main air jet:200

Idling air jet:100

Needle position: second from top

Starting Jet:85

Mixture control screw open: 0.75


Performance restrictor: slide stop

Stop pump membrane: 858 / 2,15 mm

Eddie you saved my life when I had a jetting trouble with my ex-bike (drz400). I'm sure you have cure! ­čĹŹ

Thanx from now...

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Hi guys, currently searching for a solution to EXACTLY the same problem with a 2005 EXC 250F. Standard pipe is the only difference.

Depecherider.... Does she sometimes run from nearly stalling to screaming whilst sat idling?

I substituted the carb for a borrowed one from an Exc400, ran perfectly.

The 250 has a connection for a TPS but there isn't one on the carb. could this be an issue?



Edited by Barneytrouble
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  • 3 weeks later...

Barney's bike is the RFS engine with 37mm carb

Depchech's is the RC4 motor with the 39mm carb so no relationship

On Depchech's two "must dos"

1: The needle is deathly lean in lower throttle range, the OBEKT needle "T" is the size before the taper starts, we need "P" or "Q". The "P" is KTM part number 59031034100

2: The "pump membrane" you mention, not certain if that is the stock one or not, if stock the accelerator pump is too agressive and basically floods the engine if you twist quickly, 2007 had a hole drilled for a "leak jet" (first KTM to have this) but they have a plug or undrilled jet. we need a leak jet (called power jet in KTM books) about #60, KTM #54631085060

If you want to order a couple of those to tinker with the last two didgets are the size in mm, you currently have 54631085000 (no hole) and might want to try a 54631085040

The Decell poping, that is a air leak at the head pipe, ignore it or try to seal it

If you still have the performance restrictor (this is NOT in US models) order 57331032000

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