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Discussion Starter #1
I'm wondering if anyone else has ever had this happen. My son's 200xc recently got a complete top and bottom-end rebuild. I bought the parts from Rocky Mountain, but had a bike mechanic do all the work. After two weeks we got the bike back, took our time breaking it in, and then started taking it on rides. About the 3rd ride we took (maybe 6 hours of riding after the rebuild) the bike bogged to a stop and we couldn't get it started. Pushing it back to the truck my son was able to bump start it but he said it sounded weird so he quickly shut it off. I take it back to the same mechanic and watch as he takes the cylinder off... and the piston and crank are covered in what appears to be oil saturated clay. The mechanic said he's been working on bikes for 40 years and has never seen anything like it. He said dirt or mud was getting into the engine through the airbox. Eventually the combination of dirt, oil and heat caused the spark plug to stop firing and that stopped the motor.

Could the dirt have entered the motor through a faulty seal or any other way? The air filter didn't have much dirt on the surface, but there was dirt caked around the base where the air filter joins the airbox. The mechanic has spent his life working on bikes, but has only done a few KTM's. Is there anything else that could have caused this to happen? Before going on that last ride we noticed some oil leaking from somewhere around the drive sprocket... but it only leaked when the bike was on it's kickstand. When it was on the bike stand (level) it didn't leak at all. Any thoughts?
 

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Oil leak from l/h side: If you have oil coming out when bike leans to left you have a worn seal on the main shaft out from the gearbox (where the front sprocket sits). There also is a steel sleeve that goes over the shaft and an O ring that fits inside it. Is the O-ring there?? If they are then the shaft seal that sits in the motor casing is worn.

If you have oil leaking from the oil plug that has the magnet in it (also on left side) the coppar washer is missing.

The 2009 had the older style of air filter. Easy to get it wrong when fitting as in a tight space. If you have done a crappy job when fitting the air filter you will see where the dirt has gone in under the filter. We always use grease on the mating surface between filter and boot.

If the carbi was poorly fitted to it's manifold to the motor your bike would not have run, or run crappily. If the air boot that connects the carbi to the airfilter was poorly fitted to the carbi you would have the motor sucking in dirt through there.

Without being able to see the bike and how it all looked I would focus on the following areas:
  • Make sure carbi is well fitted to the boot that has the airfilter.
  • Make sure you fit the airfilter properly (First time my son was left to do this alone the result was a seized engine...) Chek and double check every time!!
  • Use grease on the mating surface between airfilter and intake boot!
  • Make sure your airfilters are of a good quality, has no rips or holes and you oil them properly before use!
 

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Your engine does not produce gunk on its own, so the most likely cause of gunk was an external gunk contamination of the internal parts of your poor motorcycle. I suspect that your contamination was probably caused by a poor fitting or damaged air filter. The description you gave indicated a clean filter with dirty edges. Typical for this sort of problem. I’m afraid your mechanics good work has all gone to hell and needs to be redone. The abrasive crud has ruined the engine. Best to replace air filter also. KTM air filters are sometimes a pain to get fitted properly, but it has to be done correctly. See my posts in tips and tricks thread for air filter service. Good luck to you. Check back as needed
 

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Discussion Starter #4
Thanks "Axzon" and "augiedoggie" for your excellent feedback! When I returned to get the bike the mechanic showed pictures he took of the airbox and reed cages... they were both covered with dirt that had got sucked in past the air filter. And you were right about the seal needing to be replaced, so I had him replace that as well. This was a costly lesson to learn. Thanks again for all your insight, I'm sure it will help others as well.
 
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