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Pop off pressure for Moster Walbro carb


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est 12 psi.  i had alot of problems with my carb settings .thus checking the color of the spark plug.after each flight to see how how its running.and thats what you can do.....   but because i come from a mx back ground and know abit about engines. i decided to buy a brand new carb.and all my carb problems. went. it took ages for me to solve the problem. hope this helps.this is what worked for me.

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Walbro wb 37

Reseat pressure 14÷12psi never less than 10

Optimum popoff 14÷18psi

My own experience  12psi popoff pressure its to loow ,very often under vibration running engine needle valve its not seal properly and give to much fuel

You can get new metering spring from

Rowena carburetor part no 98-192

This set you stright thrue to 16psi popoff pressure


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Just did carbs on my two Mosters, Pop off and re seal was ok on first one but second one was pop off at 12 psi and re seal just under 10 psi. I fitted new lever and spring and this gave a pop off of 20 psi, I cut off one turn on end of spring which gave me a pop off of 16 psi, just shows fitting new parts can some times not give ideal settings. Idle is much smoother on second engine now. I like this forum where people share their Knowledge

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Yeap 16 psi its really good

But if you like more smooth midrange revs you can do this http://www.webring.org/l/rd?ring=2fly;id=1;url=http%3A%2F%2Fwebspace.webring.com%2Fpeople%2Fbf%2Fflphg%2Fidle_adaptation.html

Throttle plates modification give really preaty job

On photo from link its walbro wb32 and wg8

But walbro wb32 are exactly the same like wb37(exept valve control membrane in wb37 not installed)

I personally make and recommend do this .


Edited by Dariuszk24
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I read about this modification years ago but just tried it now, The Moster starts far easier and idle is a lot smoother, what a difference. I managed to unscrew the butterfly valve flap from carb no problem, I got a good fitting screw driver and put my finger in carb from other side to support shaft as not to bend it.

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Did the butterfly valve mod on my wb32/solo210 some years ago, and also plugged middle jet with a steel wire, much better throttle respons and leaner mid range (was awful, something was needed to be done). Super happy with how smooth it is since then. Recommend to try if any of the two common problems exist.

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Problems that I fixed by doing a butterfly mod are:

1. Doesn't work well when idling. The mod means a small jet of air passes directly over the jets and means the engine idles indefinitely without bogging or 4 stroking.

2. Poor control of mid-range. The mid range control improves dramatically, and it feels like the throttle response is much easier and smoother to control. This isn't surprising when you see how the mod works, you are never shutting the butterfly valve completely.


The other issue which can be fixed is the wire through the high jet described by casper above. I've not bothered doing this, but the mod basically restricts fuel flow and will lean the engine a bit, only for the high end. The default with this carb is to run rich at the high end (and there's no screw to modify it).


Sadly the carb is not tuned specifically to the paramotor engine when you buy it, but it's easy to mod to make it run way better.

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The other issue which can be fixed is the wire through the high jet described by casper above.

On wb 32/37 you have a two low/mid jets, the second is the one you can plug, not the high jet! Be careful so you don't mix it or you will lean out and destroy your engine quick.

If butterfly mod is enough, (recommended to all engines that need to have a tight screwed in idle), then stick with it. This gives a bigger throttle range, good for smoother acceleration and more precise throttle control.

If mid range is way to rich and feels like a problem, consider doing the jet-plug mod, but careful and check your temp on mid and high range so you are sure not to lean out. In other words, don't do it if you don't know how to do it in a controlled way, recommend to look at CHT, EGT and RPM. This should only be done if everything else is correct, right fuel mix, new spark plug, clean carb and correct settings. You still have to re-adjust the needles after plugging the jet.

Read the guides to get a good understanding how the WB works


In the last link he says, "advanced pilots can try blocking the #3 jet, then screw the HI needle ¼ anti clockwise, you also need a clean butterfly disc......(no notch grinded in)"
It works perfect with both mods, but since you get more air on idle you have to be careful, easy to avoid any problems if you just re-adjust from a rich setting.

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