Oil very black

[Octain]

Sounds like dude's gonna do a topend no matter what.

[Nessism]

I had the engine completely apart before it was running and you could eat off of the internal parts and casing. I'm using Castrol 10W-40 and yes it's brand new oil everytime hahaha

The UK variety Castrol is good for motorcycles, but not the US/EPA mandated (reduced zinc/phosphorus) version. Get some diesel oil.

[matt1100]

oversize rings are for oversize pistons. standard ring on standard piston. Just paid 29 and change for mine from cheap cycle parts.com, good price but they are draggin ass getting them here

[JEEPRUSTY]

oversize rings are for oversize pistons. standard ring on standard piston. Just paid 29 and change for mine from cheap cycle parts.com, good price but they are draggin ass getting them here

What bike? More info please.

[tkent02]

It's an air cooled engine, oil turns black quicker than it does in a Toyota. Looser clearances, less constant temperatures, we tend to wring the schitt out of bike engines a lot more often, the clutch is in the same oil as the engine, the transmission gears chew up the oil molecules, and some other technical reasons I can't think of right now....
It's just the way it is, the oil turns black.
The lubrication is still working, go out and ride it fast enough that you can't think so much.

[tkent02]

Sounds like dude's gonna do a topend no matter what.

We get that a lot around here.

[Potts4]

Thanks for the mega-welcome!!
So I don't have to worry about the compression being on low side (110-130psi)
I have put on about 1000 miles since the rebuild and have changed the oil three times.

[DanTheMan]

You should be fine. Do your next oil/filter change in 1500 mi., inspect it then. Keep track of your oil consumption as well. Use a high quality diesel certified oil such as Rotella.
I still can't understand why you tore it down to parade rest and didn't just do the rings at that time though.

[Normk]

If the oil turning black is bothering you more than any other aspect of operation then try a non-detergent oil which are marketed for vintage vehicles. Non-detergent or straight mineral oil stays much cleaner than modern formulations so that should solve that issue to some degree.

*Note* that I don't suggest that this is a good idea! It is not.

The reason that the oil is turning black is that it is picking up, and holding in suspension, carbon particles (mostly colloidal) which are the result of partially burned fuel blow-by past the rings. The only way to reduce the amount of this material is to either reduce the amount which the oil is carrying, resulting in that material being left in the engine, or to reduce blow-by of unburned fuel.

Some others have referred to the fact that these engines are less "tight" than newer designs of automotive and this is certainly correct. What you may wish to consider is whether the degree is markedly greater than for similar motorcycles operating under similar conditions.

A rich air-fuel mixture will tend to produce lower combustion temperatures and more carbon particles which will contribute to greater oil contamination but this may not have as great an effect as anticipated.

Wear/poor sealing of the piston/ring/cylinder walls will contribute to blow-by and elevate the carbon content in the oil. Short runs and cooler operation will also elevate carbon particle production and so oil contamination.

The most fundamental question relates to whether this is an issue which requires overhaul (I note that you used the term "rebuild" but since you didn't rebore with new pistons & rings, the term does not apply). I agree with others, just ride it.

You may be advised to check to ensure that the jetting is not overly rich and that the "choke" is off completely. If you are in the habit of warming the engine up before starting out to ride, this can contribute to the oil contamination and is not advised regardless of the "myth sayers".

[1948man]

Ride it hard for a few thousand miles and if you recheck, the compression may have risen. That's assuming the bike hasn't been run regularly over the last few years.

[Billy Ricks]

If you are in the habit of warming the engine up before starting out to ride, this can contribute to the oil contamination and is not advised regardless of the "myth sayers".

Learned that when I was a kid. As soon as my vehicles will roll out of the driveway I'm off. Let them warm up as I ride or drive. If you have a properly working enrichener they should pull away right after start up.

[1_v8_merc]

Black oil happens.
Every GS I've owned had this problem to some extent.

It might take around 4 or 5 oil changes, before the oil looks cleaner.

You gotta remember, most of these bikes are 25-30 years old.
As long as the bike runs good, and the oil is Sticky, you're okay.

[sedelen]

I wouldn't rebuild the engine because the oil is black, just so long as it isn't sludge coming out of it. Just ride the thing,
over time it may start to improve, change your brand of oil to Shell Rotella.

[tkent02]

Black oil happens.
Every GS I've owned had this problem to some extent.

But is it a problem?

If they all do it, and there's a sound engineering reason for it, and they have all done it since they were new, is it really a problem?

Diesels turn their oil black too, maybe every one of them in every ship, train and truck in operation anywhere in the world needs a rebuild.

You save the world by re-ringing everything, I'm going riding.

[1948man]

Diesel oils hold more stuff in suspension, I believe.