Engine oil turns black 50 miles after oil change

I have had to change my oil every 500 miles or so because it turns black after an hour of riding on a fresh oil change. In the 3 years and 3,000 miles I've put on the bike, I've changed the oil 7-8 times with Rotella and new oil filters every time.

Recently had a tune-up at a motorcycle shop and explained the problem and suggested a compression test to determine the condition of ring and valve seals. They were going to look into it but didn't get around to it. However, they did adjust my valves which seemed to make the bike run a little smoother.

The bike runs well and only smokes out the left exhaust pipe when I goose the throttle and it doesn't appear to burn any oil because my level stays constant. The only changes from a stock bike are K&N pods, and an emission control hose system that was removed. What is wrong with this picture, and why is my oil turning black immediately? I thought I had a lot of carbon build-up stuck inside the bowels of the engine and ran some seafoam in the oil for a few minutes at idle right before the oil change but that didn't seem to make the oil stay cleaner any longer. I've done this a couple of times right before an oil change with the same results. Fresh oil was still heavily contaminated and black after 50 miles. It seems maybe a piston ring isn't properly separating the exhaust fumes from the engine oil, but the bike seems to run well and it seems like it wouldn't run this good if it needed rings. However, it does backfire at start-up before the engine is completely warm-which sounds to me like a tell tale sign that something isn't right. Any ideas what is wrong with this bike?

seems normal for diesel oil to look dark fast,i run rotella T in my tractors,does pretty much same thing.but maybe its just me

if you do a compression test and all is within spec and the oil doesnt stink of gas, you could be scooping crap out of oil pan with the seafoam....a lot of these old bikes have a lot of shit/smeg in the pans....i plan on pulling mine this winter just to see what kind of trinkets i find and to put in a newer oil pump.......keith

these little motors burn the oil black and then it get's blacker......imo ...if you change it a lot...good for you...but if you wait till it's been a few thousand.....then ...oh well..it is still gonna run till the comet gets here....mine has seen 33 yrs and i'm sure folks did not change it with great oil and ofetn very much.........that said i change it often now..and as keith said...it gets a bit cleaner each time:woohoo:

maybe the oil is workingas designed and cleaning crud out of the engine. You wouldn't believe the scum you find in the bottom of old oil pans. Gravity alwys gets it's way with sediment particles.

It could be a few different problems, but if the bike runs fine, and compression numbers are good, changing the oil frequently is your best defencive weapon.

Keep up the good work.

I run rotella in mine, and it does seem to come out darker when the oil is changed, prob due to the make up of the oil.
I am considering going to a bike specific synthetic but as of yet I have not done it.
run a compression check, if nothing else it will let you know where you stand with the motor.
you didnt say anything about the history of the bike,and adding seafoam to it may also help in cleaning out the oil system.

rottela is designed for diesel engines which are inherintly dirty so the oil has a detergent built in to it to aid in clean up of sludge and crap that is a by product of combustion. the benifits of the additive package that is in the diesel oil far out wieghs the appearance of the oil so i would keep using it and not be so concerened about appearances just keep to your oil change scheduale and you should be good.i also just noticed that your changing the oil every 500 miles you don't need to do that, go to 1500-2000 if you got that 500 mile oil analized it would be virtually new i'm sure.

I just put Rotella in my bike for the first time yesterday. i will have to keep an eye on it to see how it looks as time gos on. I used to use Wall-Mart Synthetic for years and changed the oil at the end of each season ONLY. That is about every 10-12K miles, dependent on the season. That oil was not even dirty than.

Ok, thanks for all the feedback. I was concerned that I was "wearing out the engine" prematurely by continuing to run black oil. But it sounds like this is not the case and that the new oil is not too abrasive on the internals even if it is black. Time for a compression test. Thanks again.

I've just winterized the bike for now - removed battery and treated gas with Staybil. Performed oil change about 100 miles ago (2 months ago) I hope to avoid gumming up the carbs and fuel system over the winter here in Minnesota for a clean start in the spring. When it gets warmer out, I'd like to run a compression test on it.

As far as the history of this bike, I know that it has been garaged (with fluids) most of its life. It was assembled at the Lakewood plant in Colorado and has spent most of its life in New Mexico at 6500 + feet. It's never been thrashed, raced or laid down as far as I can tell. I just had new valve cover gaskets installed because it leaked oil out the top of the engine. When I moved to Minnesota, I asked the motorcycle mechanics whether I needed to change the jets or settings on the carburetors to compensate for a return to sea-level riding and they said no. Since the move it has been more difficult to start than it used to be.

Castrol GTX looks black in the sight glass window within a few days of an oil change but it seems to be doing it's job.