Motorcycle Repair: 1975 Honda XL175, overflow tube, carburetor body

Question

1975 Honda XL175   After sitting up for about 5yrs. i have my 1975 Honda XL175 running again... This is after cleaning the tank, new spark plug, new points, carb rebuild, and fresh oil change... The only problem i am having is that when i run it the overflow hose to the float bowl leaks gas... i have adjusted the tang on the float many times but can't get it to stop leaking gas out of the overflow tube... any help you can give me would be greatly appreciated...

Answer
Bob, nice clean original bike....

Take the float bowl off and hold the float up to where it should shut off.  The float level setting is 22.5mm FYI.

If the float tang is contacting the float valve at the correct float level setting and gas continues to flow, then the needle/seat is dirty or damaged. Unless the tank and petcock are hospital clean, often little bits of stuff can work their way down the fuel system and lodge behind the float valve, leaving a little debris behind to keep the needle from closing all the way.

If that is not the case and the rising float is shutting the fuel off, then remove the float and check it for pin holes and fluid inside one of the two floats. If the float has gasoline inside the lobes, then it won't rise properly and shut off the fuel. Inspect the float for any tiny holes and shake it, listening for anything rattling inside, which will probably be a liquid.

With some of the aftermarket carb kits, the float bowl gasket is not well made and bulges inwards, contacting the float before it raises enough to shut the fuel flow off. Check the float for signs of rubbing contact with the gasket. Many of the rubber parts in carburetors now react with the alcohol in the gasoline, causing them to enlarge and distort.

If the float has been twisted, it can alter the float shut-off point. Be sure that both sides are even with each other.

I'll assume that you put the gasket in between the float valve and the carburetor body opening.

If the float valve isn't exactly the same size as the OEM one that was in the carburetor, then the height of the float needle or location of the float valve seat may be altered from specs.

Bill Silver