New rings produce scraping sound - crank turned by hand

[smealy]

Hello all, long time reader, first time poster here. I have used this site to guide me thru a rebuild project, and can't tell you how many tips i've stolen and branded as my own.

So I'm finally buttoning her up after a top end rebuild - new rings, lapped valves, new rubber, and gaskets. After installing the pistons and securing the jugs and heads, I went to turn the crank by hand and was greeted with quite the unpleasent sound. It seems like one of the pistons (or rings) are scraping along the cylinder walls. I kno this its the theory behind rings, but it seems unusual because it's only apparent in one cylinder. The resistance of the crank is not smooth, quite intermittent actually, but there is close to no resistance when the pistons are at TDC and BDC. Is this normal? should I have used more oil? I would dissasemble to make sure everything was situated, but I'm hesitant to do that, because I have already compressed the gaskets, and skeptical that they can be "re-compressed". Maybe add some oil in spark plug hole?

 

[HoughMade]

Did you use any lube on the cylinder walls when assembling? If not, I wouldn't even try to turn the engine without oiling the cylinder bore....and more.

 

[smealy]

yes oil was used to lube rings and cylinder walls. I used my finger to disperse the oil across the entire length of the cylinder.

I did use a buddy's honing tool, so the manufactures X-hatch is no longer there.

 

[drewpy]

did you clean the bores with solvent after honing?

did you trap/twist a ring when feeding the pistons in the bores?

valves timed correctly?

pistons in right way round?

 

[smealy]

Thanks for suggestions. I may have trapped a ring when inserting the pistons into the bore. Pistons are oriented correctly, timing chain was not hooked up when I heard the scraping. Sounds like my scenerio is not normal, and will have to dissasemble again to diagnois. Do i need to replace the head gasket now that I compressed it already? Also the gasket between crankcase and jugs?

 

[smealy]

I took another look at it last night, and I just don't know what I was concerned about. When I turn the crank, the pistons and rings sound fine. They seem a little tight, but that is expected. The rings must not have seated properly and made me think something was wrong. After sitting overnight, the funky sound has disapeared. Thanks for the feedback boys - Soon I will post some pics.

 

[xschris]

Good to hear

 

[Greasey Fingers]

I like a story with a happy ending!

 

[drewpy]

good result