After two pump type primer failures I trashed that idea and went to a good marine primer bulb. I flew one on my Bee for about 3 1/2 or 4 years without a problem and I'll keep using them. What Tim said is important. You really need to plumb in a bypass around the bulb for safety pruposes. I have mine st up so it drives fuel to the carb bowls all the time, but the primer line works off the same bulb via an inline valve. So my start up procedure is:
1. close the primer valve
2. squeeze the bulb to fill the bowls
3. open the primer valve and squeeze the bulb to prime the carb throats (the carb bowls are full and therefore force the fuel into the primer circut).
4. close the primer valve and start the engine
There is no danger of leaving the primer valve open, as the engine will not run right until it is closed.
My 2 cents. Anyway, it has worked flawlessly for me for years.
I hope it helps.