When doing my pop off pressure test I have to also plug my fuel pump inlet along with the fuel out side. Is this normal? It's not blowing out the pump inlet but it leaks out so I have to pump like crazy to get it to 38 psi if I dont plug it, I have replaced the diaphragm twice and still doing so I'm not sure if this is normal, my carb it the o ring type
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787 pop off test question
- Thread starter drake1
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JeremyD615
Well-Known Member
No, that’s not normal, and will cause fuel flow issues at higher higher rpms/engine loads... I would go back through and look at your check valves. If you replaced the round clear check valves, you may have put them on backwards. They are actually slightly concave, and they will leak if installed backwards. The other common problem with them is poking a hole through the grommet during install.
Sportster-2001-951C-Stock
Well-Known Member
Concave side of check valve disk goes against the seat. I'm curious though, if not pressurizing through the fuel inlet and sealing off the fuel return, where is your pop-off pump connected?
Edit: You must be connecting to the fuel feed for the 2nd carburetor. I'd pressurize the fuel pump inlet and seal off the 2nd carburetor fuel feed b/c you're testing pop and not fuel pump check valves, which can leak and throw off your pop test. Some minor leaking of the fuel pump check valves can be normal, the volume of these passages is quite small so any leak will look large when air is involved, when these are filled with liquid fuel the story will be completely different.
I test the fuel pump by simulating the pump pulse using mouth pressure and diesel fuel for the liquid to judge how well the pump operates. Other liquids can be used as well, such as 2-stroke oil (more viscus, but works) depending on which flavors you prefer. Well, surely you're not in the habit of taste-testing?
If the leak you're experiencing is large though, might have a look at those check valve disks, no holes in the grommets!
https://www.winderosa.com/files/Download/instructioncheckvalveinstalation.pdf
Edit: You must be connecting to the fuel feed for the 2nd carburetor. I'd pressurize the fuel pump inlet and seal off the 2nd carburetor fuel feed b/c you're testing pop and not fuel pump check valves, which can leak and throw off your pop test. Some minor leaking of the fuel pump check valves can be normal, the volume of these passages is quite small so any leak will look large when air is involved, when these are filled with liquid fuel the story will be completely different.
I test the fuel pump by simulating the pump pulse using mouth pressure and diesel fuel for the liquid to judge how well the pump operates. Other liquids can be used as well, such as 2-stroke oil (more viscus, but works) depending on which flavors you prefer. Well, surely you're not in the habit of taste-testing?
If the leak you're experiencing is large though, might have a look at those check valve disks, no holes in the grommets!https://www.winderosa.com/files/Download/instructioncheckvalveinstalation.pdf
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Do not put pressure into the pulse fitting.
The fuel inlet is where your gauge is connected. On the MAG carb just connect the out and return hoses with a loop of hose. On the PTO carb just put the gauge on the inlet and your thumb over the return fitting.
Better yet follow this.....Carb Rebuild Thread
The fuel inlet is where your gauge is connected. On the MAG carb just connect the out and return hoses with a loop of hose. On the PTO carb just put the gauge on the inlet and your thumb over the return fitting.
Better yet follow this.....Carb Rebuild Thread
Sportster-2001-951C-Stock
Well-Known Member
Hopefully nobody is pressurizing the pulse fitting beyond 5psi!?!?
The carb thread is a great reference thus the link helps most everyone seeking high competence for these mikuni carbs.
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