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jdwilson

Honing Cylinders

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steve-wis

I have a flex hone that I use all the time. If there is alot of wear I have the ability to bore cylinders so I don't hone alot of stock out of them. I have two sets of stones, one coarse and one finer. I don't know the grit of the stones, sorry. I usually rough it up good with the coarser ones till any scratches are gone, then just enough with the finer ones to finish it off. Your cross hatch marks should be aprox. a 45 degree angle to each other. I believe the hone should run between 400 and 700 rpm, and do NOT go more than a quarter to a third of the length of the stones past either end of the cylinder or else you will start to bell the ends. I use atf thinned with a bit of kerosine for honing. Make sure when you are done you clean the block really good, get rid of all the grit.

Hope this helps you.

Steve

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powerking_one

Jeff,

Looking at the pictures of the bore, it looks like the "light" scoring is more than that and they are deeper; most likely due to dirty oil causing them. The darkness in the groves are probably from combustion carbon deposits. If you try a flex-stone hone to break the glaze, I'd bet the vertical scores will remain. Also note the oily top of the piston. IMHO the cylinder will need to be bored to the next over-size to do the job right.

Tom (PK)

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leeave96

How do these flex hones compare with ball hones? I've heard both terms used to describe hones - so I gather they are two different styles?

When you hone a cylinder, how much meat are you taking off - .001, or more and how do you know when to stop?

I've got a 10 hp engine that the cylinder bore looks OK and am thinking of doing a hone on the cylinder, but have never done this - so this is a great topic.

Thanks!

Bill

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powerking_one

Bill,

"Flex hones" are synonymous with ball hones. They are not very aggressive with material removal. So they just basically rough up the cylinder walls (say less than 1/4 of a thousandth of an inch or so) when running the hone up and down the bore for 1-2 minutes (with oil). This slight roughing is to promote break-in and faster seating of new rings. It will not correct bore geometry problems or scoring in the bore.

The 3-leg spring loaded type hones do the same thing, but are more aggresive and are used to finish the bore surface after an oversize boring operation and typically take off the last 1/1000" of the desired final diameter.

Tom (PK)

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steve-wis

Maybe because of a different part of the country, but I call the spring loaded three stone hone a flex hone. This as opposed to a true cylinder hone, which has two stones and two guide bars. These hones have a knurled nut that when tightened, applies much more pressure to the stones. these hones can remove alot of material very fast. In my post, I was referring to the spring loaded, three stone hone. A ball hone to me is one with a round ball stone on the end of each wire that comes out from the center, much like a bottle brush. These are for light scuffing of the cylinder wall only and remove almost no material.

Sorry for any confusion. I also agree that the bore you are picturing may need to be bored out, but I would try a hone first to see what happens. You can always bore .010 over if it needs it.

Steve

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powerking_one

Steve,

I agree in your comments about terminolgy/descriptions of the various types of cylinder hones out there. See the link below for what I described about the "ball" stone type of hone/glaze breaker. No big deal; peace...

http://www.brushresearch.com/flex-hone.php?gclid=CMTWof3uzbYCFcx9OgodJWkAEg

Tom (PK)

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Kenh

Are the rings in the photo the old rings or are they the new ones? If new they have too much gap indicating a worn bore.

If you can catch your fingernail in the scratch, I would vote for re-boring the cylinder and new piston.

Ken

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jdwilson

Those are the old rings. I put them in to show the gap. This is really a pretty long story. Suffice it to say the lawn mower repair shop that assembled this engine, after a block repair, is no longer in business!

rps20130418_184428.jpg

The man that did the aluminum welding did a an awesome job! I only wish the assembler did the same.

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powerking_one

Jeff,

As Paul Harvey used to say "now for the rest of story". When this engine threw the conn-rod, right there and then (including the cylinder scoring evidence, dirty crankcase, free extra ventilation in the block), this was obviously a seriously abused and mantenance neglected engine. To me, this would have been a no brainer for the best long term fix; a new short block, another used 8hp engine, or repower with the 10-12.5HP series. I hate to imagine what this "repair" shop charged you for this "rebuild" service.

JMHO,

Tom (PK)

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