Yamaha pop-off specs.

wjw · 07-28-2009, 04:48 PM

Hello, Bill. Do you know what the pop-off pressure would have been on a 2001 xl-700. Mine is all stock. I have done the carb kit thing and using the original springs (1.5 needle seats) the pop off was over 50 lbs. I used shorter ones in the kits and put it back together with 48 lbs pop-off. ,. My original problem with this ski was loss of top speed. After my carb work I have same problem compunded with boggy low power. Have read Mikuni tuning page, and am pondering higher or lower pop-off?

wjw · 07-28-2009, 07:17 PM

As an addendum, have read SBT tech post re pop-off. Seems to me if the motor starts easily and idles well, then the pop-off is not too high for the system and will not affect idle to high-speed transition?

Bill O'Neal · 07-28-2009, 08:02 PM

I believe those motors had like 51 psi or something like that, very high pop off.

To know your PO is good, the motor needs to start easily, run clean at low rpm, accellerate nicely to full rpm, then react well when getting into and out of the throttle at speed.

wjw · 07-29-2009, 12:44 AM

Thanks for reply, Bill. I think I'll restore pop-off with original springs tomorrow. Can't reason why its so high, but I'm no mechanical engineer!

Bill O'Neal · 07-29-2009, 01:29 PM

When you see a carbureator with very high Pop Off pressures, you know that motor has high manifold pressures. ( lot's of vacume in intake manifold ).

C Holmes · 08-14-2009, 09:29 PM

I have a Suzuki engine in a Tigershark and also am having pop off issues. I can't seem to find out what it should be. It is a 640 single carb. The original spring was well over 50lbs but it started very hard. I changed it to around 35 and it will not start at all. almost like not getting fuel at all. 130lbs compression. rebuilt carb (kit) no lines plugged. can't figure it out.

Bill O'Neal · 08-17-2009, 01:00 PM

I would try raising the pop off pressures and installing a primer kit.