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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!
 

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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.
 

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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.
 

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Any chance we can get a look at the oil via a picture for diagnosis?
 

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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. 😢
 

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My 2 cents, milky oil is water/oil mix. Gray oil sounds like worn out aluminum somewhere...not good...
 

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Discussion Starter #8
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.
Thanks a lot for the reply, we are using Castrol GTX 10w 40, not sure on the fuel level but no drips or wet spots under the bike. He sometimes shuts off the gas but not always (he is 19 :) ). The oil does not smell like gas, no different than the oil in my own bike.
 

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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.
We do check the oil as you mentioned and we are using Castrol GTX 10w 40. I do believe the oil is in about the same place as when I last changed it, but I will keep an eye on it. I left the fuel on to see if it increases the oil level. The bike is kept in our garage so I dont think anyone is messing with us. I appreciate the response and will post if I see a change in the level.
 

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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?
 

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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
 

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+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.
 

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Hi Lexiyntax, I have changed the oil I think 3 times in the past 6 months or so but will do it again and see if it starts improving. I have never adjusted the valves, could this moisture or whatever to get into the oil?
 

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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.
 

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Hi Bokobob, according to the Seafoam website it should be fine to add to the oil. I think I will put like 1 1/2 ounces in and have him ride it for a few miles before I change the oil. Whats the worst that can happen :) Thanks for the suggestion!
 

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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.)
 

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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 - I am a (former automotive OEM) engineer. Still an engineer but not in automotive now. I broke out my nerdy engineering spreadsheet mentality when it came to choosing an oil for the Rebel (The Piglet). As much as I resisted using Rotella (I'm a Valvoline Premium Blue fan for diesel applications vs Rotella), I chose Rotella T4 for the Rebel. FWIW.

The T4 conventional meets all the (recalling this from memory) JASO testing spec's. But just doesn't carry the certification(s). I would be skeptical of this, if I didn't have direct experience with similar situations in engineering life. I'm not an oil expert regardless of engineering background, but it seems oils for diesel applications tend to have whatever materials in them to help suspend particles better than the average engine oil. Because, like my Cummins diesel pickup, the engine tends to pollute itself with soot. And Premium Blue suspends it / carries it well and gets rid of it in the filter and at oil changes. I find this a good aspect for an air-cooled engine. That and Rotella T4 is OK for wet clutches … and is inexpensive. I could not find any information on the Premium Blue that it met all the same specifications that I found right on the T4 bottle.

All that blathering aside, might I suggest you try T4 next go around? It may look less clean when draining than you might like, but it is a sign that the oil is carrying deposits versus letting them remain in the engine.

As for your son's clutch, unless he says it is slipping to the point of causing rideability issues, I wouldn't bother replacing it.


7milesout
 

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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.
 

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Discussion Starter #20
7milesout, what weight do you suggest for the Rotella? Looks like they only have 15w-40 and 10w-30, I currently use 10w-40 and live in the northeast, so cooler climate.
 
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