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Smoking oil and antifreeze

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I've been riding this rm-z250 for about 6 months. I ride mostly trails and stuff, haven't been riding it too hard. Been taking care of it, changing the oil and filter regularly. It started smoking several weeks ago and it smelled like antifreeze. Due to the well known design flaw of the single water cover / oil cover I replaced the cover with a Pro Circuit two piece. I also replaced the gasket. Since that time the problem went away but returned the last time I was out. It seems the problem is with the separation of oil and antifreeze around this area but would like to know if anyone else has had this problem or if anyone thinks the smoke could be caused by anything else.

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Maybe the gasket on the water pump cover is not in the groove perfectly and allowing antifreeze to get into the oil. I have never had this problem, but youmight try getting a new gasket.

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I doubt antifreeze can get in the oil at the filter area. The oil is under pressure at the filter. It would have to happen when the bike wasn't running and the cooling system still had pressure from being hot. But, a passage allowing this to happen would allow oil to get in the coolant when the bike was running. This bike also has a water pump seal and an oil seal on the pump shaft with a weep hole in between so unless that hole is stopped up the 2 fluids can't mingle there either.

More likely you have a blown head gasket or possibly a cracked head, especially since you ride woods alot. Make sure to also check for a warped head when it's apart. The other place to look is the pipe plug located in the bottom of the hole beside the spark plug hole. It is visible with the valve cover off and is used to plug a casting hole. It takes an allen wrench to remove it. Possibly it just got loose as it is steel and the head is aluminum which expands at a different rate.

To pressure check the coolant system you can apply 10 lbs of regulated air pressure into the system thru the radiator overflow tube with the cap still in place. Apply it slowly. Pull the exhaust pipe off, and the spark plug wire and kick the motor over. (you don't want it to start) Look for signs of coolant being blown out the exhaust when the valves open. If it is present there the problem is somewhere in the head. If none shows up relieve the pressure and remove the radiator cap. Drain all the oil from both drain plugs and move the bike sideways back and forth to get as much oil out as possible. Reinstall the cap and pressurize the coolant system again. Dump the drain pan, wipe clean, and put back under the drain holes. Then move the bike back and forth and see if any coolant appears out either oil drain plug. It will come out and separate into drops in the drain pan. This is how I found our leak.

I had modified the coolant routing, splitting the outlets from the head by installing a pipe nipple where the aforementioned plug is located and routing the flow from that side of the head to the left radiator. The nipple had cracked at the threads allowing coolant to escape into the oil. It would steam like crazy out the overflow but show few other signs of water in the oil except for a milky looking drip out the overflow pipe. I first thought it was just condensation on a cold day but started loseing coolant.

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I had modified the coolant routing, splitting the outlets from the head by installing a pipe nipple where the aforementioned plug is located and routing the flow from that side of the head to the left radiator. The nipple had cracked at the threads allowing coolant to escape into the oil. It would steam like crazy out the overflow but show few other signs of water in the oil except for a milky looking drip out the overflow pipe. I first thought it was just condensation on a cold day but started loseing coolant.

I hadn't even thought about it but those are the same symptoms I have. A lot of steam comes out the over flow, white milky stuff comes out the oil over flow, and it always needs antifreeze. I guess all these are obvious signs of a problem to many of you, but this is all new to me. I still wonder why has this problem occurred? Why would riding in the woods cause problems? Is this related to a design problem I have read about with the cam? When I take it apart can I leave the engine in the bike or do I have to take it out? Should I use all OEM replacement parts or should I replace (upgrade) them? Thanks

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Cracked head gasket is what I have found so far. I've been riding this bike for about 6 months and probably have 50 hours on it. What should I be replacing while I have the engine apart? Valves/springs, cams, piston/sleeve, timing chain?

The shop book take a proactive approach replacing parts after specific number of hours. (I don't race just ride trails.) What sort of conversion should I use to replacing parts on my bike?

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Check the cylinder head to make sure it is not warped. Heat generated from riding the bike slow through tight trails will cause the trouble. You may lose more coolant than you think and once it gets low the engine really gets hot. As the head and block expand and contract due to heating and cooling the head gasket eventually fails allowing compression to enter the coolant passages when the motor is running, which will also force coolant out the overflow, and allows coolant to seep into the cylinder when the bike is shut off. This coolant eventually seeps past the rings and goes into the oil turning it milky white. If the bike has really been run hot and low on coolant the head could have cracked also. Usually this occurs between the valve seats.

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It's been a few weeks now since I rebuilt the top end and everything is great. After riding a YZF426 '02 in the meantime I'm really appreciating this bike more. Sure it doesn't have the brute force of the 426 but the handling is awsome. (I softened the front/rear compression by two clicks off the default. Very good for woods w/ 160Lbs rider.)

I also replaced the stock chain with a EK 520 X-Ring. REALLY nice chain for about 75$. I went to a 50 tooth rear sprocket b/c I mostly do trails. Did the trick but I have to shift a lot if I ride else where - not a big surprise there.

Aside from the head gasket this bike is really durable. Kudos to the Suzuki team.

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I have the same problem the raditor seems like it doesnt wanna hold any water or coolant it all just comes out the over flow and is milky white and i have white drips coming out the the motor over flow yet there is no water in the oil..

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I also replaced the stock chain with a EK 520 X-Ring. REALLY nice chain for about 75$. I went to a 50 tooth rear sprocket b/c I mostly do trails. Did the trick but I have to shift a lot if I ride else where - not a big surprise there.

Umm why in the world would you go to a 50 rear for trails? If anything you should have gone down one/two teeth in rear or up one in front..

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