▲ 2 r/KTM
KTM 350 SX-F wouldn’t start
Symptoms:
- First ride after bike sat for a long period
- ~22 hard-ish hours on engine
- Started fine from cold initially
- Engine sounded slightly off, but difficult to compare as I normally ride my 450
- After a few laps and once warm, bike would crank and occasionally fire but would not start
- Compression tested low/borderline acceptable (didn’t record exact numbers)
- Could get it started from cold with careful throttle input, but took a long time
Once running:
- oil leaking from breather hose
- smoky exhaust
- would bog badly if throttle opened quickly
- could only rev if throttle was applied very gradually
Troubleshooting:
- Completed basic tests first including injector, fuel pump, spark, and brake cleaner into intake
- Checked valve clearances — all within spec
- Removed cylinder head — piston crown looked reasonable for hours
- Removed cylinder and found part of piston ring broken and loose
- Bore has minimal scoring/scratching
Current plan:
- Replace piston rings
- Reassemble and retest
Anything else worth inspecting while I’m this deep into the engine?
u/BeginningAuthor3694 — 26 days ago