Pop Off Test on Mag Carb

[Tman240]

I'm trying to check the pop off pressure on the mag carb on my 96XP. Obviously doing something wrong since I can't build any pressure. Can someone post a picture of which lines and openings should be blocked and which line should the pop off tester connect to.

The PTO carb was easy to check and I suspect the MAG side to be as well once I have the right lines blocked.

What about the pump cover and pump body? Shoud they be on or off?

Tom

[Bill O'Neal2]

Re: Pop Off Test on Mag Carb

The pump cover must be on if testing through the fittings on the side of the carb. Put your PO guage line on the inlet fitting (bottom fitting) and block off the top fitting line.
If it still does not build pressure, your needle and seat is stuck open. If it does pump up some pressure, make sure it holds at least 15-20 psi for a minute or more without leaking off the pressure.

[Tman240]

Re: Pop Off Test on Mag Carb

Thanks Bill. Will try it. I replaced the needle and seats but for the life of me, couldn't get pressure.

I have another question. The PTO pop off pressure is 28 PSI...in accordance with what the manual says..albeit on the lower side of the range. While rebuilding, I noticed that the low speed screw on the PTO was 2 1/4 turns out....while the MAG side low speed screw was 1 1/4 out. Manual indicates they should be 1 turn out and more importantly, PTO and MAG should be the same. Do you concur or based on your real-time experience is there a more optimum setting for the low speed screws..PTO and MAG.

Tom

[Bill O'Neal2]

Re: Pop Off Test on Mag Carb

Tom, Many times I have replaced needles and seats and not got pressure. Sometimes we all make mistakes. Open the carb and check the lever arm, spring, and make sure the bar is seated properly in the slot. Activate it with your finger to be sure it is in there right.

Both low speed adjusters should be close to the same setting. Usually between 1.25 and 1.75 turns out from closed.

[Tman240]

Re: Pop Off Test on Mag Carb

I've rechecked the needle/seat and all seems okay. I can generate some pressure now such that I achieve the pop off, in this case, 29 PSI BUT thats only if I pump it quickly. When I hit say 20 PSI or so and try to hold that pressure, it just bleeds right off down to zero. I have the needle/seat area covered in WD40 to see if any bubbles but nothing....where else could there be a leak?

Tom

[Bill O'Neal2]

Re: Pop Off Test on Mag Carb

Use soapy water on the carb body. They usually leak off at the fuel pump covers. You will see the bubbles.