Cofe
Lieutenant Commander
- Joined
- Apr 23, 2009
- Messages
- 1,883
My chain saws and weedeaters have seen many years of service so I decided it was time to install new fuel lines. Here is how it went....
My two cycle equipment are of the McCullough brand. They have Walbro carbs and have a primer bulb.
Well I decided since the old primer bulbs were getting hard and cracking, so I would bypass them and run the fuel line that came from the carb back into the tank...... well the motors didn't run well at all after this modification.
After playing around with carb settings for awhile I decided to perform destructive testing on one of the old primer bulbs. After removing the clear push bulb I noticed there were two brass jet looking orifices, they had real small holes about needle size. " I was thinking.....is the fuel regulated back to the tank?"
I then decided to put a short piece of hose on the "in" side of the bulb and tried to push air through, and suck back out......nothing.......no air going either way. Put the hose on the other fitting, and under a vacuum it would let air through, but it would not allow pressure to go through.....
Pondering this....... I decided to crush this piece of *^%@!. After this final destruction, to my surprise I found there was a miniature check valve between the orifices.
Go figure...... the primer bulb function was only to pull gas through the carb then block off any flow. And all along,,,,,, I was thinking that a primer bulb pushed fuel to the carb....... So I replaced the primer bulbs and everything is smooooooooooooth.........
I hope this helps someone else out.....caused me a headache and the wife complaining that I smelt of gas....
......like I usually smell of one form of gas or the other......
My two cycle equipment are of the McCullough brand. They have Walbro carbs and have a primer bulb.
Well I decided since the old primer bulbs were getting hard and cracking, so I would bypass them and run the fuel line that came from the carb back into the tank...... well the motors didn't run well at all after this modification.
After playing around with carb settings for awhile I decided to perform destructive testing on one of the old primer bulbs. After removing the clear push bulb I noticed there were two brass jet looking orifices, they had real small holes about needle size. " I was thinking.....is the fuel regulated back to the tank?"
I then decided to put a short piece of hose on the "in" side of the bulb and tried to push air through, and suck back out......nothing.......no air going either way. Put the hose on the other fitting, and under a vacuum it would let air through, but it would not allow pressure to go through.....
Pondering this....... I decided to crush this piece of *^%@!. After this final destruction, to my surprise I found there was a miniature check valve between the orifices.
Go figure...... the primer bulb function was only to pull gas through the carb then block off any flow. And all along,,,,,, I was thinking that a primer bulb pushed fuel to the carb....... So I replaced the primer bulbs and everything is smooooooooooooth.........
I hope this helps someone else out.....caused me a headache and the wife complaining that I smelt of gas....
......like I usually smell of one form of gas or the other......