450 EXC-Needs diagnosis

ktmkube200 · 08-29-2011, 09:24 PM

2005 450 KTM EXC which idles fine with choke on and your able to reve it up, turn choke off and bike starts to back fire, spits and stalls and your unable to reve it up. We have replaced the spark plug cap and coil. Gone through carborator twice and can't find anything. I'm not sure if this is a carboration problem or ignition problem or something else.

Need help!!

bajadog · 08-30-2011, 06:09 PM

Sounds like it's running lean.

Have you checked for air leaks around the carb or airbox?

Also unrelated possibly, but when did you last adjust the valves?

ktmkube200 · 08-30-2011, 07:58 PM

Valves were adjusted in the spring. Started cutting out on top after 3-4 rides after, then starting doing this. Thought it might be accelerator pump but that wasn't it.

Then thinking maybe ignition problem but we've been through the electrical.

Totally baffled!!

ktmpegger · 08-30-2011, 08:51 PM

Quote:

Originally Posted by ktmkube200

Valves were adjusted in the spring. Started cutting out on top after 3-4 rides after, then starting doing this. Thought it might be accelerator pump but that wasn't it.

Then thinking maybe ignition problem but we've been through the electrical.

Totally baffled!!

All of my 4 strokes at one time or another have done this and in all my cases it was the slow jet (pilot). Partially or completely clogged. It has a very small orfice and does not take much at all to clog. My wife's smallest sewing needle couldn't even fit through the hole. Had to cut off one of the wires of a very small wire brush to fit through the orfice! I would re-inspect the slow jet before you start getting crazy with it!