Gregory Bender

Petcock alignment

Moto Guzzi V700, V7 Special, Ambassador, 850 GT, 850 GT California, Eldorado, and 850 California Police models



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Because the petcocks screw directly into the tank in a bolt-and-nut fashion, it can be difficult to get the petcock both sufficiently tight and properly aligned so as to afford access to turn them on and off. As original, thin shimming washers can be used to achieve the desired results.

Thanks to Mike Tiberio for providing the following information on the Yahoo! Loopframe_Guzzi news group. In Mike's own words:

McMaster-Carr to the rescue again. They have stainless steel shim washers with metric IDs. They come in 0.1 mm, 0.2 mm, 0.3 mm, 0.4 mm, 0.5 mm and 1 mm thicknesses.

McMaster-Carr metric shim.
McMaster-Carr metric shim.

Photo courtesy of McMaster-Carr.

Gregory Bender adds:

An ID of 12 mm is needed. Since the thread pitch is 1 mm, a shim of less than that thickness is needed to achieve proper alignment. A shim of 0.5 mm will change the alignment by 12 a turn; a shim of 0.2 mm will change the alignment by 15 a turn, etc. I suggest purchasing 0.2 mm thick shims and stacking them as needed. 0.1 mm may sound like the perfect solution for very granular control of alignment. But keep in mind that 0.1 mm is very thin and easily distorted.

Spring steel shims

18-8 stainless steel shims

316 stainless steel shims

Mike Tiberio also posted an interesting alternative to the standard petcock alignment:

I think most folks assume the standard position with their petcocks. That is the plane of motion for the swinging lever is a vertical plane, parallel to the fore/aft axis of the bike. This puts the hose tap pointing inward toward the centerline of the bike.

I never liked what I consider a number of side effects of using the stock petcock orientation. The hose barb pointing inward makes removing the hose problematic, and taking the tank off without snagging a fuel line tap or fuel line is also problematic. The lever just seems tough to operate from a human factors point of view. Add to all this, the fuel line routing is tortured (IMHO).

What I have done is rotated the petcocks 90° so the plane within which the lever swings is perpendicular to the longitudinal axis of the bike. This has a number of beneficial effects (once again IMHO).

First it seems easier with a gloved finger and thumb to operate the petcock lever with an in/out motion rather than a fore/aft motion. The fuel line tap now points either forward or aft (possible since the petcocks are off in either horizontal) as necessary to ensure a short and nicely curved hose run. The hose is now much easier to remove since it isn't buried under the tank. Obviously I point the lever outward when off.

just my $0.02, you might want to give it a try.