Hi  Bought this Enduro new in Japan while there with the Marines.  My older son had it for the past few  Starts okay but runs poorly.  My son (or a shop he took it to) overfilled the trans with synthetic oil.  I drained it and refilled it with conventional 10W40.  It smokes VERY BADLY (white).  I could sure use some advice with diagnosis.  Could overfilling damage crank seals?  Pat in Utah

I tried to post an 18s video but received a message saying I wasn't "allowed".

Have you verified what is in the two stroke tank if the wrong oil was put in the other side perhaps something else is in the two-stroke tank

Thanks for the quick reply! The autolube tank is full of Yamalube 2-stroke engine oil 2S smokeless.

New members need a certain number of posts before they can upload pics/videos etc. It's to deal with bots and spammers.

Pahiker, thank you! Makes sense.

I’ve run HP four Honda synthetic in my 125 without problem. I would find it somewhat hard to believe that would be the problem with the bike, but let’s see what others have to say.

I had the same issue happen on BOTH of my DT360As. Unbelievable amount of white smoke. Both incidents were the result of the crank seal having popped right out of its bore. Even bent the keeper!

first occurrence on one 360A
 share.icloud.com/photos/04f6tPZgJrpdIbuFZZLf8teKg

second occurrence on my other 360A
youtube.com/shorts/-ag6f_QkmYY?feature=shared

I had a farm quad bike with a tank of dodgy fuel think was diesel & petrol but then again horse people so could bee some horse drench but the white smoke was unbelievable but the knocking & banging from the motor had me worried but no harm done luckily. Fuel change & all good. Was a 4 stroke though. How dies yours run apart from smoke because if it's the right crank seal out it'll struggle to run if at all depending if it's out or pushed at an angle with retainer trying to hold & it's poked one part just free of the case but will still run poorly. Best go have a look. Did they fill the Trans to the top? Couldn't see anyone doing that but then again I've had it at work with scooters & customer complaining of poor performance as it paddles its way through the oil.

My first question is how long this bike has been parked since it was out on a nice long ride?  

Oil pump check valves tend to seep and allow oil into crankcase while parked.  It can take quite a while to clear out the excess oil, the "fix" is to ride it for a while.  (I have a friend that messed around with his bike for over a year trying to fix the excessive smoke.  The one thing he never did was just get out and take a nice long ride which is all it needed)

I've seen this same thing dozens of times...  sometimes crankcase is so full that the bottom end "hydraulics" and pushes out a crank seal when attempts are made to start the bike.  But a crank seal pushed out usually makes the bike really hard to start.

Since you said it starts easy, crank seal would not be my first guess.  

Another common contributing factor on a bike that has been sitting is the little o-ring on the carb that seals the bowl to the jet setter goes bad.  Now you have a super rich fuel condition which makes the bike barely run and makes it nearly impossible to clear out the excess oil by riding it...  it gets "loaded up" with fuel as well as the excess oil.

Good luck, thank you for your service, and I hope you get it running well soon!