Author Topic: CB759f1 Piston rings dumb quesiotn  (Read 152 times)

Offline mortyboy

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CB759f1 Piston rings dumb quesiotn
« on: June 22, 2022, 12:48:10 PM »
I've just refitted new pistons and rings into freshly honed and thoroughly cleaned cylinders , having checked all end gaps and spacing are OK. I very lightly oiled the rings & pistons before installation and they all went in perfectly, after a bit of faffing.  On rotating the crank I can hear a 'rubbing' sound as the pistons move through the bores.  Is this normal? I was perhaps na├»vely expecting a nice smooth, silent rotation. There's also now some very light vertical discolouration marks in the bores, visible in the residual oil film left above the pistons after the rotation. Do these perhaps mark the piston ring gap position? Should I dismantle, check and re-fit the rings? Your advice would be greatly appreciated. Thanks.

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Re: CB759f1 Piston rings dumb quesiotn
« Reply #1 on: June 22, 2022, 01:04:28 PM »
The sound is correct, should be like a slow cutting noise from metal on emery cloth to be right when new.

It's an odd process when you consider a "new" bore, but the hone marks are very specific in that they are there to cut the new piston rings (lapping process) and get to fit precisely into their new bore/home for their working life. The rings when compressed to put them in will be likely not entirely round and this process is completely normal in running in an engine, also why you need oil change after set period to remove the byproduct of this process.

If you went to check after a few thousand miles you'll hear it as you expect, with a nice accurate seal between the two but with clear evidence of the hone Mark's remaining visible as they retain oil while the piston travels over them in use. So a very concise set of transformations follow through as you run the engine to hopefully give it a long life.

Offline Nurse Julie

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Re: CB759f1 Piston rings dumb quesiotn
« Reply #2 on: June 22, 2022, 01:14:04 PM »
Description sounds just perfect at this stage.
Im a Nurse, trust me, this won't hurt.....much !!!

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Offline mortyboy

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Re: CB759f1 Piston rings dumb quesiotn
« Reply #3 on: June 22, 2022, 02:10:07 PM »
That's great to hear, thankyou very much.  😊

Offline Trigger

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Re: CB759f1 Piston rings dumb quesiotn
« Reply #4 on: June 22, 2022, 05:04:39 PM »
You need very fine stones to hone a Honda. Too course a stone and it bur's the rings  ;)

 

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