The Walbro WG-8 Carburetor
If you want to save hours searching for info on the Internet and, much worse, not learn the hard way, check the sites and info below. There are many pilots who have become experts on how Walbro carburetors work, especially the WG-8, and I have posted their important work here. The Walbro is a simple device but it is not tolerant of rough handling or abuse. This page is specifically for the WG-8 but most of it applies to other models, as well. Remember: The WG-8 has no way to easily modify the high speed mixture except by replacing the fixed jet. The jet is only made by Miniplane and they do not offer different sizes. If you need to modify the jet size, see my tech note below. Do not consider making changes to the high speed mixture unless you install a CHT (cylinder head temperature) gauge. Failure to have a CHT could result in burning up your engine. The "spark plug color" method, on the other hand, is imprecise and time consuming. I do not recommend using it. It is for general use ONLY and is useless for any accurate jet calibrations. If you have any questions or comments let us know.
If you do not want to do the repairs yourself but have a professional do it, we can help. Please contact us for details.
Bent Fuel Metering Lever Part I - by Had Robinson
Bent Fuel Metering Lever Part II - from Walbro. The tech at the Walbro group fails to explain that the condition of too great/too little metering lever height refers to extremes. That is, when bottoming or topping out of the diaphragm occurs. This is a rare condition. If a pilot sticks with the preformed lever out of a rebuilt kit, he should be OK.
Carburetor Adjustment - by Had Robinson
Disassembly and Modification - by Wind Drifter Richard Cobb -- An excellent tech note on the intractable problems with the Walbro carburetors (especially the metering lever) and how to fix them. It has some additional notes by Had Robinson
Fuel System Test - Here is a quick and easy way to check whether your entire fuel system is functioning properly.
Jet Size Modification - by Had Robinson -- This tech note shows how to modify the existing jet in your carburetor without making permanent changes.
Parts Diagram -- This image can help you identify everything inside the WG-8. The model used by Miniplane has a FIXED main jet instead of an adjustable "power needle" and is only available from Miniplane. If you need other parts, like a rebuild kit, contact us.
Priming the Carburetor without Flooding the Engine - by Had Robinson
Service Manual - from Walbro -- This is not very helpful but has some information not available anywhere else.
Starting the Miniplane - by Had Robinson -- This can be helpful after storing it for a while.
Throttle Shaft Play - by Had Robinson -- Worn throttle shaft bushings will cause the carburetor to leak air and cause stalling or poor performance at idle and low speeds. Is your carburetor worn out?
Spring Modification and Replacement - by Had Robinson -- If you fly in cold weather or dislike
the wimpy stock throttle return spring, try this mod.
This site was last updated 04/15/14