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1998 YZ125 wont run right

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Alright so I finally got around to fixing my old dirt bike, a 1998 YZ125. The Cylinder was replayed and the head redone also. I installed it on my bike thinking everything would go as planned...well I was wrong. I had a coolant leak coming from the head, no big deal, I fixed it...yet my bike was still not idling right and sounding very very very bad. Turns out there was a rats nest in my header pipe...used a flame and power washer to hopefully get all crap out of it.

So I run my bike again still to no avail it Barely has any bottom end or top end power and won't hold a nice idle or barely want to move. So I take off the header agin and I notice this gray sludge type substance coming out the cylinder. Could this be a sign of engine oil mixing with premix? Or coolant again? There was a leak from the bottom of the cylinder but I thought I fixed that also along with the head.

Any information on what may be causing this would be awesome. I have plenty of time on my hands being that I'm still recovering from a gnarly crash on my other bike. If you guys need pictures or anything let me know to better help diagnose the issue.

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I didn't check my crankcase oil, being that all that gray sludge is coming from the exhaust port of the cylinder

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Pressure check the cooling system to confirm it isn't leaking into the engine.

 

Leakdown test the crankcase to confirm RH crank seal isn't sucking it gearbox oil.

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Pressure check the cooling system to confirm it isn't leaking into the engine.

Leakdown test the crankcase to confirm RH crank seal isn't sucking it gearbox oil.

How would I go about pressure checking the coolant system, what tools are required

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A cooling system pressure tester,

it screws onto the radiator cap's opening and pressurizes the system and also allows to test the cap separately :

 

j-24460-a.jpg

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So I drained the gear oil it looked normal nothing out of the ordinary. I replaced each seal on the crankcase. The bike still produces that gray looking sludge/liquid out of the exhaust when I take off the pipe.

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ImageUploadedByThumper Talk1447394451.155853.jpg ImageUploadedByThumper Talk1447394485.018625.jpg ImageUploadedByThumper Talk1447394546.488930.jpg

This is the gray liquid stuff, I guess there could still be a coolant leak would have to buy another set of brand new gaskets. Just want opinions as to what could cause that weird color sludge.

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quoted: I replaced each seal on the crankcase.

 

Just to confirm did you replace some crankcase seals (gaskets under the clutch cover, magneto cover etc.)

 

or crank seals (circular rubber seals that go at each end of the crankshaft) ?

 

Post a few clear pictures of the piston taken from the exhaust port.

Edited by mlatour

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