Is the diaphrams getting hard? That would stop it from pupming enough gas to run right.

Also there are 2 little screens in the Carb. they get pluged.

A rebuild kit is about $10.00 and a can of spray carb cleaner is about $5.00.

That's about the price of a replacement Carb. off the auction site.

Berrymans B-12 will help soften the diaphram.
Don't leave it on the diaphram to long, it will disolve it.
Get the spray stuff and spray it in all the passages to clean out the Carb.
You could get lucky.