The good oil

**dino3310** · 14th September 2010, 21:51

Originally Posted by Taz

One of the piston rings jobs (oil Ring) is to scrape the oil from the bore on the down stroke. If the bore is "glazed" the oil can smear past the oil ring resulting in high oil consumption. Two strokes don't have an oil ring as this is beneficial in their case (not the glazed bore tho).

is it bikes or sex you talking about

**Taz** · 14th September 2010, 21:52

Originally Posted by Woodman

Yea naa. A modern cx3 oil ring has virtually no tension and does not scrape, but relys on creating a high pressure zone under the ring and by way of cutouts/ grooves or (old school) holes, makes any oil go to the nearest low pressure zone and drip back into the crankcase.
Smooth is our friend.

2 strokes don't need oil rings because it don't matter as the oil is in the fuel and is the same mix as what goes into the squish area. (Think thats what you said)

Too smooth is not our friend. We want a little rough thats why we hone a crosshatch into our bores.

**dino3310** · 14th September 2010, 21:58

Thought so .

**pete376403** · 14th September 2010, 22:01

Originally Posted by That looks like fun

KTM oil turning black (due to combustion blow by?) Why do gearbox and diff oils turn black then?:

If its a conventional 4 stroke motorcycle engine, gearbox oil turns black because it is running the same oil as the engine. Otherwise can you provide more info about the type of gearbox that is blackening the oil?
Likewise black diff oil? (car diff?) might be LSD cones wearing. Again, something wrong.
But in the main, gearbox and diff oils do not get black under normal conditions

**Taz** · 14th September 2010, 22:02

Originally Posted by dino3310

is it bikes or sex you talking about

Bikes. I know nothing about the latter.

**Woodman** · 14th September 2010, 22:06

Originally Posted by Taz

Too smooth is not our friend. We want a little rough thats why we hone a crosshatch into our bores.

Ok explain chrome bores

The main reason for honing a cross hatch is that normal boring tends to tear cast iron and the surface is not smooth enough. When re ringing the way now is to not deglaze the bores as the best surface for rings is a bore that has been worn (rubbed) smooth by the rings running up and down them.

Another reason why to not deglaze a bore when re ringing is that the bores are often not cleaned properly afterwards and the carburundum from the hone is still embedded in the cast iron and comes out when the engine starts up for the first time scratching the bore and ring faces.

Is this still an oil thread?

**dino3310** · 14th September 2010, 22:11

Originally Posted by Woodman

Is this still an oil thread?

dunno i got lost on the first page

**Taz** · 14th September 2010, 22:18

Even chrome (nikasil etc) bores have a crosshatch honed into them.

**Woodman** · 14th September 2010, 22:26

Originally Posted by Taz

Even chrome (nikasil etc) bores have a crosshatch honed into them.

Yea you are right in that you can kinda see where there was a x hatch in the original machining in some of them, but it is very very insiignificant, and you can't feel it.

i have never seen a glazed bore

This could go on for days.

**Taz** · 14th September 2010, 22:32

Originally Posted by Woodman

Yea you are right in that you can kinda see where there was a x hatch in the original machining in some of them, but it is very very insiignificant, and you can't feel it.

i have never seen a glazed bore

This could go on for days.

You should probably use Google. There are actual experts out there who can explain it better than me. P.S they use a diamond hone on nikasil cylinders...... Why should you be able to feel it? Don't need it that rough.

**Woodman** · 14th September 2010, 22:46

Originally Posted by Taz

You should probably use Google. There are actual experts out there who can explain it better than me. P.S they use a diamond hone on nikasil cylinders...... Why should you be able to feel it? Don't need it that rough.

I will do some research, am always willing to be proved wrong, but I maintain that smooth is better.

**Woodman** · 14th September 2010, 22:52

Just found this.

Didn't think about the varnish aspect, and it explains oil and running in etc too.

http://http://coxengineering.co.uk/bore.aspx

**pete376403** · 14th September 2010, 22:59

Originally Posted by Woodman

i have never seen a glazed bore

This could go on for days.

It describes how peoples eyes glaze over when some bore keeps going on and on and on...

**warewolf** · 14th September 2010, 23:26

Just back from the pub, 'avin' a few bevvies with a recently ex-pro bike mechanic.

"Glazed bores: fact or fiction?" says I.

"Fact. The trouble is oils are too good these days!" says he.

ROFL!

Says he wouldn't have believed it himself without seeing it first hand. Their tour fleet of BMWs would burn lots of oil if run on semi- or full-synth. On mineral oil, they never used a drop and ran better. Reckons it is more of a problem with older design engines using new synth oils. He agreed that the increased lubricity of modern oils is unfortunately a problem for good ring seal (are we talking about sex again?!

). The problem is that the glazed/varnished bore is so damn smooth and slippery that you get a film of oil getting past the rings into the combustion chamber (my impression is that it is similar to surface-tension behaviour, or like the way plain bearings float on a fine film of oil, thereby avoiding metal-to-metal contact) and combustion gases getting past the rings reducing efficiency.