Nebuchernezzer
16-05-2009, 06:47 PM
Howdy, I'm newish here. I'm one of Fimp's mates :). Anyways i just rebuilt a bike I bought recently so i have some questions about tuning it if anyone knows.
I picked up a 1997 KTM EXC 250 off a mate for $500, it was in need of a top end rebuild which I did a few weeks ago. Now that it's all back together I'm looking at making it run nicely.
So far with the factory settings (jet sizes etc all taken from the KTM workshop manual) it runs and starts no worries but it does have a few problems.
At low to mid revs it stutters and carries on. It's not happy like this and it doesn't like to rev cleanly.
From mid to high revs it opens up and roars away happily, the exhaust not changes and it's great.
Free revving it doesn't sound very clean either.
I turned the air screw out another half turn from the factory spot (1.5 turns) to make it 2 turns and it ran worse.
I turned it in 0.5 of a turn to make it 1 turn and it ran a tiny bit better, but not really.
Now I have a rough idea of how the jet sizing and needles etc work but I'd like some advice on what to look at next.
Also i've got to seal the expansion chamber on properly, it leaks a bit currently, but not heaps.
The airfilter is clean (and I'm guessing even if it wasn't it wouldn't be the problem since the bike roars away at high revs no worries).
Any help would be much appreciated :).
I picked up a 1997 KTM EXC 250 off a mate for $500, it was in need of a top end rebuild which I did a few weeks ago. Now that it's all back together I'm looking at making it run nicely.
So far with the factory settings (jet sizes etc all taken from the KTM workshop manual) it runs and starts no worries but it does have a few problems.
At low to mid revs it stutters and carries on. It's not happy like this and it doesn't like to rev cleanly.
From mid to high revs it opens up and roars away happily, the exhaust not changes and it's great.
Free revving it doesn't sound very clean either.
I turned the air screw out another half turn from the factory spot (1.5 turns) to make it 2 turns and it ran worse.
I turned it in 0.5 of a turn to make it 1 turn and it ran a tiny bit better, but not really.
Now I have a rough idea of how the jet sizing and needles etc work but I'd like some advice on what to look at next.
Also i've got to seal the expansion chamber on properly, it leaks a bit currently, but not heaps.
The airfilter is clean (and I'm guessing even if it wasn't it wouldn't be the problem since the bike roars away at high revs no worries).
Any help would be much appreciated :).