Hello guys, my father and I just recently bought a Cota 123T and are in the process of restoring it to a proper riding condition. After riding it around for a day or two dark back oil starting spitting out of the exhaust pipe and we came to the verdict that it needed new seals. So we got the magneto side off completely fine but we cannot get the primary gear off even with heat and a good puller. That thing is stuck on there. Any tips on what we should do? Thanks!

Edited April 13, 201610 yr by baurespdx

Are you sure it's not just unburnt 2 stroke ? Is there a lot of grey smoke, are you lossing gear oil. What ratio of 2 stroke are you running, if 25:1 you will get oil coming out the pipe.

I don't think the drive side crank seal is gone, but if you really want to get that drive gear off, you will benefit from a very strong puller that doesn't damage the gear teeth, and cycle it hot and cold while it is loaded up. If you search in the forums you will find many discussions on the subject of 1970s Montesa Cota drive pinion removal.

Black oil dribbling out the exhaust is definitely not a leaking crank seal. It is just part-burned two-stroke oil. If you do more than just tiddling around on it you will burn more of the premix oil and lessen the goo production rate and might even clean some of the goo out. Also make sure you don't have too much oil in the premix or a too-rich fuel air mixture

Gearbox oil leaking into the crankcase forms a dense white/light grey cloud of exhaust smoke which stinks and the oil level goes down

Normal exhaust smoke is clear pale blue and smells like normal two-stroke exhaust

Yes, if it the pleasant 2 stroke smell (this is how you can tell someone has been involved with motorcycles for decades, the 2 stroke oil smells good) it's fine, if it's the "lawn mower burning oil" smell or the clapped out car burning oil smell then it's tranny oil.  

i tried to mess with the carb setting and no matter what the setting where at the engine would bog down as soon as i rolled the throttle. people were telling me it was a lack of compression do to one of the seals. we cannot get the primary gear off either... also, what kind and quantity of fork oil should be in a cota?