Freestyle Pop off question

[stefan]

soo checked my pop off the orther day and both carbs was att 21 psi, whitch was fine but one carb only droppede 5 psi before resealing the orther 15. Tryede a couple off times with gas and also WD40 same result, does this have and effect on engine performance ?

 

[Vumad]

soo checked my pop off the orther day and both carbs was att 21 psi, whitch was fine but one carb only droppede 5 psi before resealing the orther 15. Tryede a couple off times with gas and also WD40 same result, does this have and effect on engine performance ?

I'm not 100% clear what you're saying but I'm pretty sure what you are getting at.

There are 2 parts of a pop-off test. One part is the actual popoff, which you did, and got a crisp 21psi.
The second part is to test for leaks. A carb should hold 10psi for 10 minutes (although I never wait that long). I also make sure the carbs will hold the psi just below the popoff for a few seconds, like 20, just below the popoff. So, in your case of 21psi pop, I'd stop about 15-18 and wait a few seconds to see if it's leaking at all.

The point of the second test is to check everything that is not the needle. If air is leaking out but there's no bubbling from the needle, it's coming from somewhere else. Spray WD40 on the carb to find it. Air leaks around the fuel pump body are common with non-mikuni O-rings and dirty / damaged surfaces. It's also common to have leaks around the fuel lines, so use reusable zip-ties during your testing.

If your fuel pump is leaking, then yes, it will affect your performance.

In the off chance what your saying is you have no leaks and your pop is crisp, and what you are asking is about how much the gauge drops after the pop, there's nothing to worry about that. The popoff test is different than the actual running conditions where the fuel pump is constantly generating pressure. In most cases, it opens and stays open. It doesn't flutter open and closed fast enough to be concerned about what you may be asking here.

 

[stefan]

Thank you just what i was looking for.

 

[smoofers]

The pressure test (test #2) at 10 PSI is VERY important! My slave carb (the one with no fuel pump) was leaking out of the rectangular plate (where the fuel pump would be) and I ended up melting a piston. I didn't find the leak until after I blew the motor.

 

[stefan]

I did that one no issue an run dual internal pumps.