Re: New and need help.
As stated pictures would be a big help in diagnosing your issues but from what I gather by your post you are trying to make a friction drive. Correct?
If so knobby tires and a piece of slick pipe are going to barely give you enough surface tension to drive the bike without slippage (which will cut the tires down fast) let alone if you are trying to bump start it. If this is the case you are better off pull starting the engine.
And as Rohmell said it is always good to have as much support as possible on both sides of a shaft. And you are also correct that if you exert too much pressure for long periods of time on a shaft you can expect to have bearing / bushing and seal issues in short order.
On a side note no matter how you are designing your drive if you are using clamps on an aluminum frame you should make sure to put a piece of steel (like a partial section of EMT conduit) between the frame and clamp to distribute clamp pressure over a larger area to avoid serious frame damage.