Surging, died, won't start - Page 6 - KTM Duke 390 Forum
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post #51 of 55 Old 10-12-2019, 12:55 PM
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My suspicion since there was no apparent noise with the engine giving up: burnt valve(s) and/or valve seat(s)

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post #52 of 55 Old 10-12-2019, 01:15 PM
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Or detonation debris from over lean damage has fouled the exhaust valve stem
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post #53 of 55 Old 11-02-2019, 11:39 PM Thread Starter
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Well, that took quite a while, but apparently she's back to running. I got a call from the shop yesterday letting me know it was ready, but I was out of town and they're closed on Sunday and Monday, so I won't be able to pick it up until Tuesday.

The guy told me when he called that they found the root cause of the top end failure. Apparently there was a small piece of plastic that got into the engine and clogged up the oil injector, which starved the top end of oil and caused the failure.

Since the engine has never been worked on it obviously came from the factory that way. I haven't seen the plastic, but he said it looked foreign, not something inside the engine that broke loose.

Chalk one up to crappy QA at the KTM factory. I'll try to get more specifics on Tuesday and share what I learn.
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post #54 of 55 Old 11-03-2019, 03:17 AM
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Glad thatís sorted. Iím not a big fan of the sealant theyíve used between the engine cases for just this reason. Iíve seen the top end die on bikes before because someone thought that silicone was a good way to seal up the rocker cover.
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post #55 of 55 Old 11-03-2019, 03:05 PM
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For a piece of plastic to get into the oiling system it has to get by one of two screens and a filter, so it did not get into the oiling system but was probably assembled at the factory with the foreign object in place.

Glad to see they finally sorted you out.
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