Hey all.. been fighting this problem for a while and tried some suggestions from here but nothing seems to help. My son has a 2009 Honda Rebel CMX250 and within a few days after changing the oil it appears gray and milky. I have drained the puke tube and blew it out with some low pressure air but still an issue. Recently I have cleaned the carbs, replaced plugs, basic maintenance stuff. I assumed it was due to his short rides so I had him do some longer runs to bring up the temperatures but no difference. Any additional suggestions would be greatly appreciated!
tanascar
What kind of oil is he using? And what is happening with the fuel level when the bike sits with the engine off?Any indication of drips and wet spots under the bike? Does he shut off the tank valve when the bike is not running? Something is contaminating the oil, and the most common cause is fuel overflowing from the carb (float stuck) and draining into the cylinders. Does the oil on the dip stick have a definitive smell? Since your in a position now of attempting a resolution by elimination I'm posing the most obvious questions. I apologize if this is ground you have already covered. You can try to search past post threads for "discolored oil" or "oil contamination" and see if something matches the issue you describe. I would suggest that the engine not be run even after an oil change until you resolve this. As I'm sure you know if the optimum viscosity of the oil is compromised it will compromise the life of the engine. The air cooled twin relies on optimum lubrication to keep that engine from overheating leading to premature metal parts failure and destruction. Best of luck in resolving this.
Welcome to the forum.
you've already done what I would have in your situation. Because it's counterintuitive, I always ask if the oil level is checked with the bike level and the dipstick unscrewed and resting on the threads? What brand and weight of oil have you been using? Have you tried a different brand? Does the oil level remain stable or go up? To me, gray/milky oil would indicate serious moisture contamination, but that's not possible with an air cooled engine unless someone is adding it to the crankcase to mess with you or your son.
you've already done what I would have in your situation. Because it's counterintuitive, I always ask if the oil level is checked with the bike level and the dipstick unscrewed and resting on the threads? What brand and weight of oil have you been using? Have you tried a different brand? Does the oil level remain stable or go up? To me, gray/milky oil would indicate serious moisture contamination, but that's not possible with an air cooled engine unless someone is adding it to the crankcase to mess with you or your son.
I don't know if this observation has any validity but you can consider it. A link to an ATV forum site that has the grey oil issue.
www.atvriders.com/vbb/showthread.php?425725-Why-is-my-oil-grey-looking]Why is my oil grey looking?
www.atvriders.com/vbb/showthread.php?425725-Why-is-my-oil-grey-looking]Why is my oil grey looking?
I would check that the air filter/box isn’t completely soaked for some reason. Open that air box up and check that out if you haven’t.
Since we haven’t seen the gray it’s hard to say but only a small number of ways for water to get into the oil. The other option is metal flakes in the engine... Because bad things are happening. 😢
Since we haven’t seen the gray it’s hard to say but only a small number of ways for water to get into the oil. The other option is metal flakes in the engine... Because bad things are happening. 😢
My 2 cents, milky oil is water/oil mix. Gray oil sounds like worn out aluminum somewhere...not good...
Doesn't look like the milky gray I'd expect from moisture. Looks to me like engine carbon/sludge from an extremely dirty engine. Did the previous owner ever change the oil?
I would suggest trying another oil change, then running it a while and checking it again. One of the plus sides of 10w40 Castrol GTX is it is inexpensive, and the Rebel doesn't hold much. I suspect the detergents in the fresh oil are cleaning out the filthy engine. If this is the case it may take a few cycles of running for a few hundred miles then changing oil, but it should clear up.
Another possibly related question though, when was the last valve adjustment?
I would suggest trying another oil change, then running it a while and checking it again. One of the plus sides of 10w40 Castrol GTX is it is inexpensive, and the Rebel doesn't hold much. I suspect the detergents in the fresh oil are cleaning out the filthy engine. If this is the case it may take a few cycles of running for a few hundred miles then changing oil, but it should clear up.
Another possibly related question though, when was the last valve adjustment?
I agree with Lexiyntax - It doesn't look as gray as I was suspecting. I had a 2009 Honda 450X that was street legal. For whatever reason when I changed the oil it would come out graphite gray. The guys on the forum seemed to think that was normal. I never did, but the bike ran fine and I just kept it changed.
However, I want to mention on your situation. Could it be clutch material in the oil? It is a wet clutch. Ask your son how the clutch is doing. Any slippage?
And further, I would try a different oil (another that is ok for wet clutches) and see how it comes back. Castrol GTX is my go to oil for cars, but I'm running Shell Rotella T4 in The Piglet, available at Walmart and not expensive. My engine is relatively new. The last time I changed it, it came back darker than I would have expected, but I'm not sweating it.
7milesout
However, I want to mention on your situation. Could it be clutch material in the oil? It is a wet clutch. Ask your son how the clutch is doing. Any slippage?
And further, I would try a different oil (another that is ok for wet clutches) and see how it comes back. Castrol GTX is my go to oil for cars, but I'm running Shell Rotella T4 in The Piglet, available at Walmart and not expensive. My engine is relatively new. The last time I changed it, it came back darker than I would have expected, but I'm not sweating it.
7milesout
+1 on probable dirty engine.
Not recommending, but I have used 2 oz of seafoam in the crankcase and ride easy-like for about 25 miles and then change the oil.
I have done this and the drain oil was way beyond filthy and very black.. As said, not recommending. Just saying...If you do so, proceed at your own risk.
Not recommending, but I have used 2 oz of seafoam in the crankcase and ride easy-like for about 25 miles and then change the oil.
I have done this and the drain oil was way beyond filthy and very black.. As said, not recommending. Just saying...If you do so, proceed at your own risk.
Hi 7milesout, the clutch could be a possibility, he has mentioned before that it seemed to slip some but that was right after an oil change and he hasent mentioned it since, I will ask him though. I did a new clutch myself on it almost 2 years ago and there is always a chance I did something wrong.. or possibly the clutch plates were junk and are breaking down..? You think its worth pulling apart and doing a new clutch, I dont think the plates were all that expensive.
Tanascar...Good for you wanting to try Seafoam. By the way, I've had drain oil a lot dirtier than what your photos show yours to be. Recently bought another air-cooled bike and after changing the oil and running for one ride, the oil was dirtier than that in your photos. (I had no Seafoam on hand at the time, so just did the oil change.)
Make sure there is 3/8" - 1/2" of free play at the end of the clutch lever. I change oil every 1,000 miles and use Shell Rotella. It is always black when drained. As 7milesout suggested, this is more a function of the detergents in the oil doing their job and suspending combustion byproducts rather than the oil being "old".
Valves that need adjustment shouldn't cause the gray oil, but they will affect performance and engine life.
I wouldn't dig into the clutch as long as it isn't slipping consistently.
Valves that need adjustment shouldn't cause the gray oil, but they will affect performance and engine life.
I wouldn't dig into the clutch as long as it isn't slipping consistently.
I've been following this thread closely because it reads like a good mystery novel. And the questions and suggestions have all been intriguing. I'm 70 years old and have hands on experience with internal combustion engines since I was about 10. My first bike(?) was a 1964 Honda supercub C90. I have to say that in all the years of observing used oil I have never seen that grey color you photographed. For sake of simplicity I burn the Honda GN4 10/40w. And I only burn non ethanol gasoline. My '86 250 has a little over 12,000 miles and I change the oil every 1,000 miles. The oil is dark at that point but not, say, coal black. Others on this forum have their own preferences for oil which I would not dispute. However, I'm very curious about the effect (of whatever is contaminating the oil) on the oil's viscosity since that will severely impact the life of the engine, transmission, and clutch. From what I've read so far, I would agree with Guba's point about the grey color resembling aluminum. But in the second and third pics there appears to be a mixture of what I consider to be the normal dark color of used oil, and the grey-ish color. As others have mentioned, it doesn't resemble typical moisture contamination. It will be interesting to see what your son says about clutch performance. Good luck Sherlock! 
Lexiyntax - The vast majority of the time, when valves clearances become out of spec from useage, it is too much gap. The problems that arise from that are that the follower doesn't follow the cam profile and the opening ramp up becomes less of a ramp up, and more of a slam up. Which furthers wear and increases noise. And, since the valves won't push open as far, a bit less power too.
But there shouldn't be any way to affect the oil with an out of spec valve clearance.
But there shouldn't be any way to affect the oil with an out of spec valve clearance.
Looks like aluminum in the oil to me. Check the balancer chain tension. If it has too little tension the chain will rub crankcase housing and wear off aluminum to contaminate the oil. If you hold the oil in the light, you will see the glitter of metal flakes. After doing a little research it looks like you don't have a balancer chain in that model, but I'm not sure.
if oil is grey it's getting water in it, i'm not sure how that works on a rebel but it's like white smoke out the exhaust. it's always water in the oil. it can also completely destroy your motor/anything else that oil touches. it's likely a seal somewhere, i'm not talented enough to tell you how to determine which one other than checking every one which means replace every seal after you check it. basically you have a defcon 6 issue with your lube off the top of my head i really can't think how water would get into that motor depending if you store it outside in a monsoon or not.
Quick update.. I put seafoam in and had my son put some miles on it and then changed the oil using the Rotella. After the change, he took it for a quick ride and about a week later (finally got the time) I checked the oil and same grayish look. Also noted the level when I did the change and a week later the level did not change (at least a notable change). I have recently found on other sites people having close to the same issue and it was due to having aluminum clutch plates. I changed the clutch last year but not sure if the plates were aluminum. Upon very close inspection of the oil, I think it does resemble super fine particles of some sort of metal. I am going to remove the clutch cover and see if I can see anything. The last time I replaced the clutch I only did the friction plates, not the steel plates, should I have done both? The plates I used was these https://www.amazon.com/gp/product/B00KS735Y8/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1
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