Inside a blown-up RC390 engine......it happened to me

s30series

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So some of you might remember me- I joined this place a long time ago. I was told by my dealer I was the first person in the state of GA to take possession of an RC390, MY2015. I left this forum and said "see ya!" a year and half back when the motor decided to lock up in the N. Ga mountains.

Story: Bought the bike from a dealer in S. Atlanta in 2015. Did not go to a MMS because I had a bad experience there buying my Yamaha Bolt. Early on in the bikes life- airbox plastic cracked and nipple on top of radiator overflow bottle somehow was broken off. Took it to MMS instead of purchase dealer to get warranty work done. They refused- saying the bike was modified. I threatened mag. moss. act and they fixed the rad. tube by drilling out and sticking adapter in- and wouldn't touch airbox. I basically said "i hope your dealer burns down" and left, promising myself to never return. So far so good, bought an XSR700 from the same place in S. Atlanta as the KTM. Anyways- I didn't want to take it down to S. Atlanta so I just lived with it.

Fast foward 4k miles and a year or so- we went for a mountain drive and my friend who rides Vespas rode the KTM. At one point me and other friend didn't see the KTM behind us- so we turned around. Found him on the side of the road. Said he heard an absolutely horrible noise, the oil pressure warning/light came on the dashboard and it was hot. I got on the bike and from I recall it was not overheating- just a little warmer than usual- attributed it to mountain riding (high revs, low airflow, etc). Drove it around and it sounded fine. Checked oil- level looked good. Nothing wrong. Decided to head home and I'd ride the KTM. Started riding slowly with low engine load, and engine would squeak. I knew it was toast and about a mile later full throttle and 0 power- at that point it locked up.

Left the bike on the side of GA400 hoping someone would steal it- left for a month for some Army training- got a call from the police about it. Finally came up there with a truck and took it hope where it sat for 18 months.

Well- I ended up selling the bike to friend for very little money and he has the time/space to take it apart. Two days after picking the bike up from my place it's already in 1000 pieces- and here's what I found.

IMG_20190804_200137.jpg

I'm a stickler for starting a motorcycle and instantly getting on and riding it under low load until the water temp goes up. Really thats how I treat anything with a motor. This is 5k miles- cross hatching is still perfect. Piston had no scoring on it- skirts showed "normal" wear on the coated pad.

IMG_20190804_200153.jpg

This is obviously the water pump impellar. Looks like its been chewed up pretty bad.

IMG_20190804_200158.jpg

Behind the impeller. My friend thinks its scratches- I'm more inclined to think casting/machining markings? Talking about the concentric circles here. Obviously water and oil mixed- there is a fine grey powder/slime in here.

IMG_20190804_200758.jpg

Yikes. This is interesting. The cam bearings on the opposite side of the chain are TOAST. Head looks simliar (see below). Oil jets are clear of debris. So odd to me that the ones opposite cam chain got destroyed and not the ones closest to it. Strange.

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Once again- so strange. Only one rocker arm is toast (back intake). I'd like to look at the oil passage diagram to see how the flow of oil is....perhaps the very last place oil goes is that back oil passage (above the spark plug in the picture)? Cam lobes are not ground down, however they have a nice rainbow color to them do to I'm assuming overheating.

The rest of the motor has not been taken apart (crankcase, etc) but I'd like to know what he finds in the bottom. It seems the stars aligned to blow this sucker up.

This happened 6 months our of warranty.

I can't for the life of me figure out what happened- we ate dinner at my friends house last night and I couldn't sleep because I was running things through my head.
 
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ReidMcT

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That is very strange indeed, and, like you, I'd be wanting an oil circuit diagram to ponder.
 

ReidMcT

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And here it is. Rather poor quality, but it does show that your damage is at the end of the line. So, either a blockage or - most likely - an oil pressure problem. Bad pump? Clogged filter?
Oil Circuit Diagram.JPG

Checking oil pressure calls for a special fitting that replaces the oil filter cover. An annoying expense, not to mention wait time for shipping probably from Austria.
 
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