Old really bad oil in the crank of my 175.  

I have done a lot of top ends and never have I seen this before.  It’s was filled to the brim with bad oil from years ago.  Level did not change when I drained the crank case.  Just got the bike, no history on it.  Cylinder and piston looked ok otherwise.

I Was hoping to just do a piston and cylinder hone and reassemble.  Bike has not run in 10 years.

any idea what caused this or what I need to do?   

The first thing that needs to be determined is that there’s no water in the bottom end from being left outside in the rain. Once that has been identified’ that there is no water, the engine needs to be taken out of the bike turned upside down and drained. It’s possible that you can use diesel fuel or Marvel Mystery Oil for a few days to soak the bottom end before you turn it upside down a second time and see if it spins and feels smooth? If it doesn’t, it needs a total tear down and rebuild of the complete bottom end. Normally, when this happens - they have 90% water. 

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Whomever did that [filled it up for longterm park up]might've save the day. Or more likely the oil tank has gravity fed through the pump then water got in [if it was outside with plug out] & the oil is sitting on top of water. How's it feel to spin over on kickstart with piston off & bungy cord from the conrod up to the frame.
Hope it sounds good--no growls. Better drain it [as Asco said above] & see what it shows--oil water mix.
Be great if these long term parked bikes could talk.
Re-thinking, if someone put it in then i guess old oil is better than full of water.

Greetings from Tennessee. 
  was the cylinder and head off when you got it if not probably the autolube drained in there from the tank from sitting a long time because of a bad check valve

First thing to know is this is a two stroke... you drained the transmission, not the "crankcase".

Crankshaft on almost all two strokes is sealed from the transmission and is lubed by oil that is mixed into the fuel.

Hopefully not full of water... I've been lucky, the several I've had like that have all been full of oil.

That said, VERY common on a bike that has been sitting that long for oil to seep past autolube check valve as HT1kid said. Check valve might not even be "bad"... 10 years is a long time and just a drop of oil a week adds up. First thing is need to suck out or pour out as much of the oil as possible.

Harbor Freight has an low priced orange hand pump that does remarkably well at sucking out oil. www.harborfreight.com/multi-use-transfer-pump-63144.html Turning it upside down might be better though.

I wouldn't be surprised if head pipe on exhaust was full of oil too?

Thanks for the advise, turns smoothly, i sucked the oil out with a oil removal pump from the bottom, no water was observed in the suction tube or in the collection tank once removed.  Love the idea of mystery oil for a bit to condition the area.  THanks!

Yup Pipe was full of oil....the bike has been stored intdoors since 1985 and ridden up to 2011, when it was "put away".  the sellers husband passed but he had a bunch of these old bikes and knew how to take care of them, Its possible that it was done as preservation, the rest of the fluids were brand new, Auto lube reservoir was full of clean oil not this scummy stuff.

I plan to:
-Fully drain, "rinse" with some clean oil, drain again
-replace the crank seal on the clutch side (replace clutch disks in the process)
-hone the cylinder and put a weisco piston in (i have had great luck with them but i am open to other thoughts)
-rebuild the auto lube

Anything else i should consider?


 

Thank you. I would absolutely try to obtain a yamaha piston. Even if you’ve had fantastic luck with weisco get a general consensus from the group about siezco pistons. 

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I love Wiseco pistons, never gave me trouble. Early ones came with rings that absolutely needed the rings filed to set the correct end gap... just like most "performance" rings did back then, even for cars. Too tight on the ring gap will cause problems including seizure. Modern ones don't have that issue and computers/technology/metallurgy have fine-tuned the shape to where the clearance doesn't need need to be as big as it used to be. One drawback is the "steps" between bores is twice what Yamaha offers.

Nothing wrong with Yamaha pistons either... In my opinion it's false economy to hone and swap pistons. Send the cylinder to someone like Bill Bune and have it measured and bored to next oversize if you're going to do something. Enduronut likely has piston and rings at a good price.

I'd replace the ignition-side crank seal with the true double-lip ignition side crank seal from the 77-79 IT175... (was also used on YZ125's of that era)

Oh, and if Autolube tank was full of fresh oil, I'd bet it was topped off recently... you're seeing what used to be in the tank.

You could also check the check valve at the pump outlet... often a little bit of swarf gets in there... not sure what year you have but not hard on most to remove fitting/spring/ball to check and clean.

Thanks! i plan to rebuild the pump (well i got a rebuild kit anyway now i just need to find instructions).  Doubt the oil in the tank was recent it was clean, but clearly old and thickend up with age, the owner died several years ago and it has not been touched since.  

Ill do both seals, i just ordered the tools to pull the stator.