Cub 70 motor smoking

[cub1961]

Getting started on my 2nd refurb, this one being a model 70. Looks pretty original and runs good except for the smoke. puffs a lot of blue smoke on startup and pretty much anytime i accelerate. So far my experience is on all the "easy" stuff, wiring, steering, carb, valve adjustment, ignition, etc and haven't torn into a motor or trans yet. What would be a good plan short of a complete teardown? just pull and clean the head and replace gasket, check for slop in piston, cylinder condition, etc? How would i tell if it needs rings if the rest looks ok? i would like to get this one ship shape but am hesitant to rip into the engine since i have not done it before. any advice would be appreciated.

 

[HKCooper44]

The last Model 70s were produced in 1965, so if you have the originally installed engine, it's at least 59 years old. Who knows what had been done (or had never been done) to the engine in all that time! If you're serious about this tractor, and if the engine rins and doesn't knock and bang, you can leave the engine alone to puff smoke. Or you can spend about $150 on parts (as I did on a '64 Cadet 100) and plane the head, hone the cylinder, and replace the piston, rings, rod and valves. Once the head and sump are off, why not?