KTM Owners Forum banner

1 - 7 of 7 Posts

·
Registered
Joined
·
5 Posts
Discussion Starter #1
My mate recently bought a new bike, a 09 250 EXC. He previousy owned an 07 model.
The bike being new is completely standard.
On part throttle and low revs, the bike seems to splutter and bog down slightly, which, when riding technical routes, leads to problems with the bike stalling.
He was running 50-1 mix but has increased this to 60-1.
Carb has been pulled apart by two different bike shops and no problems found.
Any ideas what would cause this??
The 07 bike had a FMF gnarly expansion chamber fitted, would this smoothe out the botom end. Different reeds maybe???
 

·
Registered
Joined
·
5 Posts
Discussion Starter #3
Jetting is standard. Plug and plug cap have been changed, still the same problem, spluttery on part throttle.
His 07 ran sweet as a nut but as stated, that had different pipe. Those pipes are not cheap but if that solves the problem then worth it.
Just seems very strange a bike thats "ready to race" with only a few hours on the clock has this problem!
 

·
Registered
Joined
·
104 Posts
A mate has a 30 with a Gnarly pipe, madde a big difference to low end power, the pipe is good so i'd look elsewhere for the problem, sorry can't be more specific but it narrows it down,
 

·
Registered
Joined
·
109 Posts
Sounds like a possible yet issue if it's 'spluttering', for what they cost i'm suprised a jet change isn't one of the first things thats tried...

Has the mixture screw been adjusted? made any difference? EG, bottom end better, rest worse or the opposite

Has he tried doing a plug chop at low throttle to see what the fuelings like?

Has either of the bike shops stuck it on a dyno with a gas analyser up its bum?

All process of elimination stuff thats not all that easy to do over the internet lol
 

·
Registered
Joined
·
5 Posts
Discussion Starter #6
He took it back to the ktm dealer he got it from and they said they set the carb up.
He was still not happy with it so took it to his local yamaha dealer, who in turn contacted ktm with regards to the correct jets and he already had those fitted.
I'll mention the plug chop to him, thats a simple task he can do himself. If thats ok, then the gas analyser is a good thought.
My own opinion would be to change the expansion chamber as this made the 07 much more responsive.
 

·
Premium Member
Joined
·
31,506 Posts
I would try raising the clip on the needle a couple of notches to see if it crispens up.

Is the float height set correctly? Does it leak fuel if you shake the bike with petrol turned on and motor stood?

You do know that by altering the premix to 60:1 you have richened the air/fuel ratio and you will need to lean the carb to compensate?
 
1 - 7 of 7 Posts
Top