04/25/12

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 WG8, 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 WG8 but most of it applies to other models, as well.  Remember:  The WG8 has no way to easily modify the high speed mixture because the Miniplane version has no high speed needle adjustment.  If you need to do this, 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 will likely result in burning up your engine.  The "spark plug color" method is imprecise and time consuming and 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. -- Had Robinson

If you do not want to fool with your WG8 but have a professional overhaul and check it out, you may send it to us.  Please contact us for details.

Common issues of the Topo80 and the WG8 carburetor - by Had Robinson

Calibration & Modifications for the WG8 - by Gerry Farell (This is one of the best articles on the WG8.)

How to Modify Jet Sizes - by Had Robinson (These notes show you how to modify the existing jet on your carburetor without making permanent changes.)

Installing a Cylinder Head Temperature gauge (CHT) - by Alex Varv  We can supply a rugged CHT for $99 + shipping - contact us for details.  Note:  Most 2 cycle engine manufacturers specify a max head temp of 250 degrees C.  Ordinarily you should not exceed 200 degrees C.)

Metering Lever Problems - from Walbro (What happens if you accidently -- and easily -- bend the metering lever.)

Pop Off Spring Adjustment - by Mike Forbes

Pop Off Spring Adjustment - by Alex Varv (Info on how to use home made tools to measure the pop-off pressure.  There is debate on whether to modify/cut the spring or just replace it with one of a different value.)

Slow Midrange Adjustments - by Alex Varv (Alex adds to the info on the midrange problems of the Walbro and how to fix them.)

Reading Spark Plugs - if you insist on doing this, here is the best way to do it.  However, if your motor is running very rich, this is an inexpensive and easy way to tell.  Most pilots should NOT change their spark plug from the manufacturer's specification unless they are skilled.  Remember:  The gap must be correct for the plug to do its job!  If your Top80 sputters at full throttle and lacks power, it is likely a spark plug with too great gap.

Walbro Carburetor Dimensions - by Gerry Farell (This sheet compares the dimensions of the various Walbro carburetors and is helpful if you are considering upgrading from the WG8 to another type.)

WG8 Disassembly and Metering Lever Issues - by Wind Drifter a.k.a. Richard Cobb (This is one of the best tech notes on the intractable problems with the Walbro carburetors and how to fix them.  BTW, I have confirmed that the metering lever height for the new diaphragms should be 0.75mm. - Had)

WG8 Parts Diagram  Note: The WG8 model used by Miniplane has a FIXED main jet instead of an adjustable "power needle" jet -- part#40.  This fixed jet is only available from Miniplane.  If you need specific parts, like the tune-up kit, for your WG8, contact us with the number of the part you need.

Walbro Service Manual - has some important info missing which is supplied on this page