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I normally only work with really old engines often abandoned for a long time and in that case typically hearing crunchy or scraping noises when moving the piston is undoubtedly a bad sign and warrant at least taking off the head and inspecting the bore.

That being said I am now looking at a "new" engine. I put it in quotes because the engine has 0 hours on it but it has been stored in its original package in a storage locker for a couple of years. The engine is a small engine, an 168F chinese diesel engine:

Engine picture

Before running the engine I filled it up with 0.7l of engine oil according to the manual, the dipstick is fine. I gave it a couple of pulls with the pull start and the decompression engaged and could already hear a scraping sound when moving the piston. I did not think much of it, its new, probably barely lubricated yet so might as well be.

I used the electronic start afterwards again with the decompression to get some oil pressure going and splash it around and get things lubed up. When using the pull start again the scraping did not get much better. I ran the engine for a few seconds and there you cant really hear the scraping, but as soon as I stop it and use the pull start again it does sound crunchy...

My thoughts are this is some sort of breaking in procedure? Getting things properly seated together, like rings and bore. Is this normal in new engines? I would like to make sure I am not chasing ghosts here and start tearing the engine apart to inspect whats going wrong :)

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  • Sounds like the sort of noise that will self-clearance after a few hours of runtime :-)
    – Criggie
    Nov 20, 2023 at 0:57

1 Answer 1

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I actually decided to go ahead and just tear into it no matter the answer and can make the following statements:

  • Bore and piston rings were absolutely immaculate and there was no scraping whatsoever
  • There are magnets glued to some kind of tin that is then screwed to the back of the flywheel for the charging system. All 3 screws that held the tin with the magnets to the flywheel were for some reason not tight meaning the tin with the magnets was sloppy and could move. Also 2 of the 3 screws snapped when getting them out... It should not have caused the noise as there are magnets all over it which should have kept it at equal distance from the stator everywhere.
  • Even though the engine did also seem completely new from the inside it has a massive dent at the bottom of the blower housing which I think also slightly bent the sheet of metal holding the electric starter
  • The flywheel rubbed against the bent sheet from the starter over the length of approximately 5mm which caused the noise

So to answer my question above: No, also a new engine should probably not make any scraping sounds :)

P.S: I made the executive decision to simply grind down the bent sheet of the starter where it touched the flywheel since it was too thick (around 4mm or so) to bend back and the noise went away.

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    Please do not forget to check your answer as the answer. Nov 24, 2023 at 12:12

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