Update-It starts, idles, and revs, but rev is kinda slow. Do these have a centrifugal advance mechanism? I put a chain on it, and rode it up and down the block twice, hoping the smoke would clear out. This things smoked like a locomotive. Maybe it's because of the premix I put in the tank...
Maybe it's a crank seal too, or the exhaust is full of oil?
I took the dipstick out while it was running and the RPM went super high, so I stuck it back in. Would a bad crank seal make it do this? or is that what happens on a running 2 stroke when the crankcase is opened up while running. My gut tells me something is amiss there.

Would a bad crank seal make it do this?   YES

So should I start with the right side? are both left and right seals something I can change without scattering the entire engine?

I was hoping it was just too much oil with the premix and the autolube, but the way that idle took off when I pulled the dipstick... I've never seen an engine do that

2strokenewb, this is my DT360, right side cover removed.

Right Side Cover Removed:(note, this is during disassembly; new basket case has been installed for those that note it is broken)


Crankshaft drive gear and seal. To remove, stick a rag between the drive gear and clutch gear. I use an impact.

Note, the seals on the FAR RIGHT are the "castle" seals and the good ones.

So, the rag will prevent the crank gear from turning the clutch basket? I can do this with the clutch basket in place?

I tried to buy those seals, but seller is on break until Friday

Thanks all, for the looks and responses

I had the same issue with both of my DT360As. The link below may be helpful. Start at post #54 thru #60. Good luck!

www.yamaha-enduros.com/index.php/forums/...ish-me-luck?start=50

Two stroke crank seals must seal pressure and vacuum...  original seals are "SW" type with two spring-loaded seal lips that accomplish this... basically two seals in one.  

 

The plethora of "inexpensive" seals on ebay are "SD" seals with one spring loaded lip...  the second seal lip is a rudimentary "dust seal" and does not have a spring.  While these seals might work "okay", they generally will never seal as well or as long as original type.

Castle turret bumps on original seals are there to prevent pressing them in too far and restricting the oil to the main bearings.  The seal lips themselves on original seals are specially coated to be low friction and last a long time in the harsh environment. 

There are MANY reasons to go with OEM SW seals!  The drawback is they can be harder to find and sell for about $45 each on ebay.  The others are about $30 for both on ebay...  and even less at a bearing supply house.

Both OEM seals were available on ebay when I just checked. 

And yes, basket MUST be removed.  Pay careful attention to the way the discs and thrust washers are installed!!  Take pictures!  Do NOT rely on exploded parts diagrams to assemble as they are not correct in most cases.  And use an inner clutch hub holding tool when loosening the nut.  Never try to hold the inner basket with the outer basket unless you want to buy a new outer basket after you break off an ear or two. 

I would also suggest an air or electric impact for the crank nut...  remember to loosen before removing clutch. I've shredded rags and destroyed pennies trying to wedge the gears and remove the nut without an impact gun.  

Thank you Mark, for the well explained post. I found the NOS seals on ebay and bought them as well as gaskets for both sides. Isn't there also some sort of oring for the kicker shaft hole?

I have both electric and air impacts

I do not have the tools for the clutch basket removal. Can I buy these? any recommendations on what to get and what to avoid would be greatly appreciated

It's cleaning up nicely considering it sat abandoned for so long

The fuel and oil tanks on that bike look great.

For reference:

Clutch Basket Tool:
www.amazon.com/gp/product/B09LYGT9Q8/ref..._title?ie=UTF8&psc=1

Kick starter Seal:(no orings except on the crank gear where main seal is I recall an oring there)
www.partzilla.com/catalog/yamaha/motorcy.../dt360a/kick-starter