TOPIC:

There's been some criticism over the years about the difficulty in turning (selecting) the 1300's original fuel-valve lever. I had the same issue with my 1980. When the bike was up to temperature the valve was extremely difficult to turn. I fixed this issue very simply. On the back of the lever is a "tab" that engages a notch in the tapered plastic valve cone. This couples the two to turn as one. A small (but stiff) spring fits between the two pieces and is intended to apply an inward pressure, forcing the cone to fit snugly in the tapered valve body.
The problem ( in my opinion)is an inherent design-flaw: When completely assembled and the face-plate screws are tightened the tab bottoms-out in the cones notch and crushes the cone into the tapered bore. This renders the function of the spring useless and applies a permanent force on the cone that increases with heat expansion.
I reduced the "tab" height by about .040" and the problem was fixed. The tab now "floats" in the notch, the spring now functions as intended and the fuel-selector lever now turns VERY easily in all conditions. As the fuel-selector body (pet-cock) heats up there is now some room for the cone to "adjust" by creeping out of the taper the few thou. needed to remain "rotational" while the spring ensures a reasonable amount of pressure on the cone, ensuring a leak-proof fit.
The entire procedure took 20 minutes.
If the fuel valve leaks from the front, it suggests the o-ring needs attention. Leakage from the fuel-outlet when selector is 'OFF" indicates the Cone is not all the way seated for some reason or (and more likely) the mating surfaces of the Cone and the tapered Bore are damaged. The damage is likely in the form of scratches on both due to foreign material from the tank. Rust and scale being the primary suspect. This is why keeping the in-tank filter is a good idea. The plastic valve-cone and the tapered bore in the body itself can be lapped-in with an appropriate compound. Make up a fitting that will engage the slot in the "cone" and you can spin it in the aluminum body with a low-speed rotary tool such as a drill. Some light to medium scratches can be removed using this method. It worked for me!

Scotch:

Good to know.

hola scotch podrias poner una foto de la herramienta que fabricaste para arreglar la valvula de combustible saludos


Hello Scotch,
Could put a picture of the tool you made up to fix the fuel valve?
Greetings

No picture required - I used a file to reduce the tab height and a larger flat-blade driver was fitted to the cordless drill to spin the cone in the bore. You just need to center the bit in the slot so it spins concentrically and found it easiest to hold the valve in-hand.

Also sometimes the screw that holds the selection lever in sometimes bottoms out and binds on the body of the lever, a small flat washer gives a little bit of clearance, hope you don't mind if I throw a few photos in so new people know what the inside of one looks like ??, I am not trying to hi-jack your thread, apologies if I overstep the mark ...

Good pictures of the fuel valve ! Two types on the carb'd version. I believe the one pictured is a '79. The 80's and up used a separate chrome face-plate and it's two screws to retain the cone assembly.
A good point regarding the style pictured. The single retaining screw could cause some interference so adding a "shim" washer would alleviate that concern. The "tab" on the back of the selector lever is what requires it's height to be reduced to avoid "crushing" the cone into the bore, which is why the valve is difficult to turn and becomes very difficult when things heat up.
With the height of the engaging tabs reduced the spring shown can now do the job intended of applying an inward pressure to maintain a consistent tight fit of the nylon cone to the tapered bore. If the cone or bore are (lightly) scratched the two can be "lapped" together using a light abrasive compound. I used a slotted screw-driver head in a cordless drill to spin the cone. The success of this will depend on how badly the two pieces are scored. Scratches (gouges) that are too deep will require the valve be replaced as the valve will leak when shut off. The scratches/gouging of the cone and or bore will result from the in-tank filter being removed and (typically) rust and other debris making it into the valve assembly.