[SEL] piston rings and bores.

[bill at antique-engines.com]

Rings need to "Wear in" and with a glaze, there is nothing to cause the
rings, or the cylinder to "wear to match". The cross-hatching also
actually holds oil causing an even better seal and REDUCING friction.

If this were a car, there are different types of honing to match different
ring constructions. There are measurements for the "roughness", actually
scopes to measure it.

In your case, simply "deglaze" it, make sure it's as round as you can get
it, taper is nill and you'll be fine.

Bill


> In this case John, removing the glaze has done it ,top compression and no
> blow back out of the breather.
> ----- Original Message -----
> From: "John Culp" <johnculp at chartertn.net>
> To: "The SEL email discussion list" <sel at lists.stationary-engine.com>
> Sent: Monday, May 02, 2005 7:36 AM
> Subject: Re: [SEL] piston rings and bores.
>
>
>>I dunno, I've put new rings in totally glazed old bores that weren't
>> hugely
>>enlarged or out of round and had good results. The glazing itself isn't a
>>problem with gas sealing so much as it reduces the oil-holding capacity
>> of
>>the cylinder wall and can cause problems with ring and piston
>> lubrication.
>>A much bigger problem is if your bore is worn till it's not round. The
>>rings may have worn and turned as the bore wore so they sealed fairly
>> well
>>in it, but new rings won't. They'll bridge between high points across
>>out-of round sections and you'll get tremendous blowby.
>>
>> On pulling a piston out, I always look where the ring gaps are. In a
>> perfectly round bore with free rings (not pinned), there is no preferred
>> orientation and the rings will rotate randomly over time running in the
>> engine. The gaps won't be found oriented the same way when you later
>> pull
>> the piston as when you put it in. (That's why orienting them in specific
>> ways isn't critical.) Often you find the gaps all lined up on one side
>> of
>> the piston. That means the bore has worn to an egg shape, with the gaps
>> lined up on the pointy side of the egg. That bore will have to be
>> rebored.
>>
>> John
>>
>> On May 1, 2005, at 6:38 PM, peter ogborne wrote:
>>
>>> I just rebuilt a small single cylinder ,four cycle engine. .....short
>>> cuts ,don't take them ! Because i could not readily buy new rings i
>>> made
>>> some ,no problem there but i did not take the glaze off the bore. When
>>> reassembled there seemed to be lots of compression and start up was
>>> easy
>>> . After an hours run absolutely no compression...first thoughts it was
>>> the valves . I did the usual and shot some oil down the spark plug
>>> hole....compression !That eliminated the valves as the problem .
>>> Pulling
>>> the barrel off and examining the bore showed considerable glazing
>>> ,there
>>> was evidence of blow by ,oil coming out of the breather. So now it out
>>> with the hone ...................
>>
>>
>> John Culp
>> Bristol, Tennessee, USA
>>
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>
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