u/Hot-Increase75

Hi,

I’m looking for advice on a no-start issue with a KTM I recently bought as a non-runner.

The bike appears to be a 2005 KTM 450 SX with an RFS engine, and it looks like a previous owner converted it to battery/e-start, so the wiring is not stock. I confirmed that the bike has an SX stator, SX flywheel, and correct SX-F CDI. The wiring harness has several splices/adaptations. The bike will turn over by bump starting down a hill, but immediately dies.

Here’s what I’ve done so far:

• Rebuilt and cleaned the carb
• Fresh fuel
• New air filter
• New fluids
• Adjusted fuel screw
• Checked cam timing
• Set valves to spec
• Confirmed spark
• Unplugged kill switch for testing
• Disconnected manual decompression cable for testing

Symptoms:

• The bike will not start with the kickstarter
• It will bump start, but when it starts it runs briefly, bogs, and dies
• It will not idle
• Kickstarter is mechanically working and does turn the engine/flywheel
• Manual decompression cable is not hanging open
• Hot-start plunger is not hanging open

Important findings:

• The original flywheel and stator were damaged. The flywheel had gouging inside, and the outer ring was separating. The stator also showed clear physical rubbing/damage
• I replaced the flywheel
• The crank taper and keyway appear usable from visual inspection
• I later realized I may have installed the woodruff key incorrectly. I mistakenly thought it should sit flush, so I tapped it down until it was almost flush. I now know that may have caused incorrect flywheel indexing or improper seating

At this point I’m trying to determine whether the main issue is:

1. incorrect flywheel/key installation or timing relationship,
2. carb/pilot/float/idle issue,
3. weak low-RPM ignition due to modified wiring,
4. or some combination of those.

Does this symptom pattern point you in one direction first? If you were diagnosing it from here, what would you check next?

Thank you

Hi,

I’m looking for advice on a no-start issue with a KTM I recently bought as a non-runner.

The bike appears to be a 2005 KTM 450 SX with an RFS engine, and it looks like a previous owner converted it to battery/e-start, so the wiring is not stock. I confirmed that the bike has an SX stator, SX flywheel, and correct SX-F CDI. The wiring harness has several splices/adaptations.

Here’s what I’ve done so far:

• Rebuilt and cleaned the carb
• Fresh fuel
• New air filter
• New fluids
• Adjusted fuel screw
• Checked cam timing
• Set valves to spec
• Confirmed spark
• Unplugged kill switch for testing
• Disconnected manual decompression cable for testing

Symptoms:

• The bike will not start with the kickstarter
• It will bump start, but when it starts it runs briefly, bogs, and dies
• It will not idle
• Kickstarter is mechanically working and does turn the engine/flywheel
• Manual decompression cable is not hanging open
• Hot-start plunger is not hanging open

Important findings:

• The original flywheel and stator were damaged. The flywheel had gouging inside, and the outer ring was separating. The stator also showed clear physical rubbing/damage
• I replaced the flywheel
• The crank taper and keyway appear usable from visual inspection
• I later realized I may have installed the woodruff key incorrectly. I mistakenly thought it should sit flush, so I tapped it down until it was almost flush. I now know that may have caused incorrect flywheel indexing or improper seating

At this point I’m trying to determine whether the main issue is:

1. incorrect flywheel/key installation or timing relationship,
2. carb/pilot/float/idle issue,
3. weak low-RPM ignition due to modified wiring,
4. or some combination of those.

Does this symptom pattern point you in one direction first? If you were diagnosing it from here, what would you check next?

Thank you