Pop-off Valve Setting for X30 With a HW27

Looking for information on pop-off valve, X30 Tillotson HW27.
I can find YouTube videos on carb rebuild & pop-off. I’m looking for information on adjustment/settings of the pop-off based on the track, temp, altitude etc. Any good videos out there or articles?

Essentially a low pop off pressure will draw more fuel Into the carb and run richer. Higher pop off will result in generally leaner setup. Of course, your screw settings can compensate for this to a large degree. The popoff will also affect how much fuel is drawn at peak torque

My 2c, is that consistent popoff across rebuilds is more important than tweaking it for tracks unless you’ve gone from one extreme to another and just can’t get it dialed in with the jets…

Specifically for the X30 @Ryon_Beachner from 2Wild can probably give a good baseline setting.

For example, let’s say I know before hand that a track is at 300 feet above sea level and temps around 70 degrees, what would be a good starting point for the pop-off? Or if I travel to a track that’s a mile high, what would be a good pop-off? Then I can dial it in with the Jets.

I’m looking to buy a pop-off tool during the off season and start doing my own carb rebuilds.

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I wouldn’t adjust pop off depending on conditions like that. I would pick a pop off that seems to work and tweak the needles accordingly.

We used to test different pop off’s all the time in Formula A. I don’t know why its not a big deal anymore.

I always found a higher pop off faster and more responsive but harder to drive (if you just dump the throttle you get lean spots/misfires).

If i raced regularly I would be testing this sort of thing like crazy.


That’s why I’m recommending keeping it simple… :smile:

OK, I got this info from Andy Fallon who’s Tillotson’s product engineer, so you can rely on this as a good baseline.

The X30 carb settings are quite simple. The std spring works well pretty much everywhere which is 37g (opens approx 10psi). Don’t recommend to go softer in the spring but a 42g can work well in hot conditions also.

Senior X30 Settings should be:
L: 1T
H: 1T 30-35mins

Lever flush to the metering body and should be good to go! Hope that helps…



Thank You Everyone! Great information and answers my question.

Thanks again, Wade