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Carburetor high speed jet adjustment in the Walbro WG-8

by Had Robinson

It is rare that the WG-8 will need any high speed adjustment unless the carburetor has been damaged or you are flying at high altitudes.

Before attempting to adjust the high speed system, be certain that the idle and low speed systems have been properly adjusted, the metering lever height is correct, and the fuel delivery system is working properly.  If the ignition system has any defects, starting will be difficult and the top end performance will suffer.  If the carburetor is worn out, it will not idle or run smoothly.  If the reed valve block is not torqued down properly it will leak air and the fuel pump will not work properly, if at all.  Always check these things if carburetor adjustments do not work as expected.

There is no easy adjustment of the high speed system.  That is, there is no jet needle that you can screw in or out to adjust the high speed fuel mix.  This was designed on purpose: to keep pilots from burning up their engines.

The high speed fuel air ratio adjustment of the WG-8 is done in two ways:  1.) By changing the fuel pop-off pressure or 2.) By changing out the fixed high speed main jet or modifying it.  I do not recommend changing the pop-off pressure as it requires a spring kit and a lot of experimentation.  Changing the high speed jet is easy to do.  We now have the high altitude jets, if needed, and also pop-off spring kits.  Contact us to purchase.

After adjusting the high speed system, the idle and low speed systems will have to be re-adjusted.  If you do change the high speed system, I hope you are smart enough to have installed a CHT....