Small Engines (Lawn Mowers, etc.): Garden tiller Repair, briggs carburetor

Question
Have an old garden tiller Lazyboy 5  model 12038
has briggs 135292-017001-9301082  engine.

Problem # 1 engine will not start unless I prime carb with gas . Then if stopped will restart for a limited time.

Problem #2 with engine running tines will hot engage
Engine has two output shafts going to double pulley on
shaft that drives tine chain.  There is a hand control on right side lavbeled forward but pulling in doesn't engage
tines.
Is there some type of clutch inside of chain cover ? Also
belt on straight (not reduction shaft is in very bad condition . How to diagnose problem ?
Thanks,
Alex

Answer
Problem 2 I can't help you with as I can't find any pictures or diagrams of your tiller and I just don't know how it's put together.

Problem 1 I think I can help you with.  I'm not sure I understand what you mean by will restart for a limited time. Will it die after restarting or will it restart without priming for a limited time?

This has the carb mounted on the tank doesn't it?  It sounds like you have a diaphragm that's getting weak.  Does it do this even if the tank is all the way full?  The best way to resolve this issue is probably going to be to just go through the carb and replace the diaphragm and gaskets.  

On that type carb, the diaphragm acts as a fuel pump.  It picks fuel up from the main tank and drops it in a smaller tank within the gas tank.  The smaller tank acts as a fuel bowl and fuel is picked up and fed into the venturi from there.  

So what can happen is fuel leaks out of the fuel bowl into the main tank leaving you with no fuel for the venturi and the diaphragm is to weak to pump just from trying to start the engine.  But when the engine is running, the impulse signals are much faster and stronger so the pump can keep up.

Also what can happen is that fuel bowl can rust away and leak fuel out, causing the same effect.

Also, you could have some dirt in the system causing a weak fuel supply.

This is why it's easiest to just rebuild the carb and give it a good soaking, you eliminate most of the causes at once.

Let me know if you have any questions.  Thanks, PK.