Oil mixing with my water on a yamaha dt 125 r

Are you sure this is a DT 125 as with this particular bike it is self mixing there should be a separate tank by the handle bars just under the front plastics opposite the water tank this is where you fill it with oil then just put gas in the gas tank and it will mix it self you do not have to do anything else do not put oil in the gas tank with the gas mixing would usally be dirt bikes or really old bikes only

Smoke in a two stroke motor is caused by two things. 1) Even a four stroke will smoke if it has too rich of a mixture or a carburetor that has a malfunctioning choke (a new choke plunger would fix this). Make sure you have a good o-ring on the main jet holder. This was a common problem on old Yamaha two stroke carburetors.2) The type of oil you are using is of a very low grade. Smokeless oils and synthetic oils will smoke less and could solve the problem.
You could just be seeing old residue burning out of the exhaust system, try cleaning the baffle. When you rebuilt the motor did you use a semi drying liquid type gasket material between the two case halves? This would keep transmission oil from leaking into the crankcase. If you have only started the motor in the driveway you may have to just go out for a long drive down the road to clean up all the systems.

Your barrel? LOL. Sounds like the valves need to be gone through. I would suggest taking and valve train apart and put it back together correctly then go from there.

stick your cok down the petrol hole

Assuming you are using two stroke engine oil, the pump is pumping too much into the gas. DO NOT use motor oil in the gas. If 2 stroke oil is being used, then get a new pump, fix the one you have or disconnect the pump and mix the oil with gas when you fill up. Four ounces of 2 stroke oil per gallon of gas equals the standard 32/1 fuel mix.

excessive piston clearance.really needed bore job with oversized piston,not just honed and rings.measure piston to cylinder clearance,check spcifications and verify

• If a hole in the piston then install new piston and rings. Next, clean the carbon off the head and install a new head gasket.
• If cylinder wall is scared the piston has seized up. Pull the cylinder off and take it to the dealer. Have them bore the cylinder and return it along with a new oversize piston and rings.
• While at the parts counter, get a new stock spark plug and a supply of Yamalube Two Stroke Motor Oil. You need to add 4 ounces per gallon when filling up. This will be a 32/1 gas to oil ratio. NEVER ride the bike without at least the needed 32/1 mix.

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the problem arises in this situation because the water system is mixing with the oil system? if i am right in thinking that this is an liquid cooled version with the infamous powervalve system then you might find it usuially has something to do with that. if you keep running th engine then you will find out that it will do lots of damage to your piston which relies on oil to move and cool.

hi karen, that is right, i do have a DT 125 myself and same thing has to be done.

Usually this is balance the engine so that the moving parts will move to a limited place. this is also to avoid further block damage when the piston is moving up and down.