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Discussion Starter · #1 · (Edited)
My friend's 2015 CBR300R had a terrible noise and reduced power, then it died and wouldn't restart. Once I dropped the engine and started taking it apart, I discovered that the intake shims were missing (!) and the left-side cam bearing surfaces were trashed. I pulled the head and saw scoring in the cylinder, I pulled the cylinder and saw scoring on the piston skirt, and when I stuck a magnet in the crankcase it came up with the missing shims ... plus pieces of main bearing. All of this seemed like pretty clear evidence of oil starvation even though the sight-glass had showed a good level of oil.

Only then did I remove the right side cover and discover that the oil filter had been installed backwards, and that doing so blocks oil in the cavity, preventing it from lubricating the engine. I was flabbergasted. It is trivial to come up with several simple designs that would make this impossible (starting with the obvious - a normal spin-on filter, like almost all cars and motorcycles in the world today), but somehow this design was approved and manufactured.

This engine is ruined. I could rebuild it by buying pretty much everything other than the side cases and transmission, but it would cost about as much as a replacement engine from a wrecked low-miles bike (and a LOT more work).

So please learn from this tale of woe, and remember: the end of the filter with a hole goes towards the engine. And join me in a moment of silence for this engine. Soichiro Honda must be spinning in his grave.

-Craig in Sunnyvale, CA


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Discussion Starter · #2 ·
BTW a big shout-out to lightningfrog27 (who is a member of this forum) for posting an amazing video series on youtube with details about engine work on this exact bike. What an effort that must have been. My hands are always too greasy to even take good photos; I can't imagine how much time it must have taken him to do all that video work. If you ever need to work on your CBR300's engine, you must watch his videos!

-Craig in Sunnyvale
 

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Discussion Starter · #4 ·
I'm still scratching my head over the design. Even if you wanted to have a cartridge filter instead of a normal spin-on filter (though why you would is beyond me), it's just so easy to come up with several easily manufactured designs that would make it impossible for this to happen. My friend is heartbroken over this mistake, one that I believe should not be possible to make.
 
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