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YFZ 450 milky oil, water leak?, cutting out on idle?

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i have a 2004 yfz 450 and ive recently had a full rebuild, after a few weeks i had picked up a water leak which dripped from the water pump tell tale hole, changed outer seal only and water leak stopped.

now i have a leak again aswell but dont know where from cant see any leaks also ive now got milky oil and when i remove the transmission breather pipe (the one coming from the oil filter casing) really milky water like fluid drips out probly about a teaspoon worth.

the engine runs great except after a few mins it will struggle to idle and then cuts out and struggles to restart.

also popping on exhaust when down shifting or general slowing.

ive drained and changed the fuel and drained the carb and checked the jetting,

any one have any ideas, im thinking about doing an oil & filter change and replacing the inner water pump seal while im at it.

please any advice will be great as this is doing my nut in.

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took for a 30 mile run today topped up water and kept a good eye on her as we were going and she was fine.

still lost a little water but she stopped stalling and as if by magic all the water in the sump has evaporated out.

milky oil returned to black, starts first time again and ticks over.

i reckon the water pump inner seal, a new clutch as thats been going for a while and an oil and filter change will do the trick.

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You may need a new water pump, seals, and bearing. YFZ's are somewhat famous for leaking coolant when cold and then stop once the motor warms up. Your popping was probably a plugged pilot jet that cleared itself after enough fresh fuel was run through it.

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  • 5 months later...

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