Topic: gas leak/float pin questions

[ErikP]

There are many threads about float pins and gas leaks, but I seem to have managed to come up with some more questions!

If the tip of the float pin moves freely when the rubber float dingus presses on it, that would mean the float pin is okay, right?  ie, if its stuck and gas is always flowing out of it, the float would be unble to move the pin tip....?

Also, does the normal float level stay below the gaskets?  In other words, if you have bad gaskets on the float bowls, would gas just keep leaking out, or does the gas not normally stay that high.

I have been having some leak probs.  I changed out the rubber piece in the petcock (which was worn) so that at least I can stop the gas at the petcock.  However there was gas coming from a few of the carbs at the gasket area.  I took off one of the bowls, and the pin seems ok, so I'm not sure if that means the gasket needs to be replaced?

Any help would be great!  This is a 72 CB500F.  Curious too - what kinda mileage should a well tuned CB500 get?

-Erik

[Bob Wessner]

Also, does the normal float level stay below the gaskets?  In other words, if you have bad gaskets on the float bowls, would gas just keep leaking out, or does the gas not normally stay that high.

When floats are set to the correct height, the max fuel level should still be below the gaskets. If the level is at, or above them, the float height is not correct or they are not functioning correctly.

[TwoTired]

Bob is correct, provided the bike is upright or on the center stand.  If the bike is on the side stand, a leaky bowl gasket will weep until the fuel level depletes below the gasket level.  Also, inertial forces will slosh fuel to the gasket level and weep.

Regardless, if the gaskets are leaking, they need to be replaced.

The float needle tip or seat can become damaged or blocked with debris and leak.  Simple movement is no guarantee of seal.

In stock form, the CB500 should get 40-50 MPG depending on tune and what gear and speed you predominately operate in.  If you spend all your time in first gear or neutral and 7000 RPM, expect 10 MPG...about.

Cheers,

[cafehonda]

One thing I have found is to polish the pins with Mothers mag polish. I also took the time to polish the floats inside the pin area. I used a wood dowel and some of the Mothers polish. Clean well with lacquer thinner or carb cleaner. Also, if you have the carbs off the bike, take the time to make sure the floats don't hang up on the sides, even when at an angle. I've seen a lot of bikes that seem to have floats that hang up when leaned over but seem to never leak when on a center stand. A little judicious sanding with 1000 grit on the adjacent parts will often times take care of this problem. Be careful, don't remove too much.
    good luck, Dyno.

[motorcycleclaude75]

Hey,

On my bike, I get great gas mileage, about 120 miles on a tank.  Of course this depends on your driving habits, on a nice country road I've seen over 50 MPG, most of the time the average is about 45 which is great.

I've still got the original engine that has over 50,000 miles but I keep it well tuned.

I suggest you buy a carb rebuild kit and get them done unless you have the ability.  WARNING, this is not a cheap process, but once you get it done, you will notice a difference.  Keep in mind,once you work on your carbs, I suggest you synchronize them to get the full performance.

After I had my carbs done last year, my bike ran better, stronger and I got better gas mileage.

Claude

[ErikP]

Thanks for all the feedback.  I think I'm going to hold of on the float gaskets until I have some other things to do in there - for now at least with a working petcock and keeping it on the centerstand it doesn't lose any gas at all.  For now it seems to ride ok as far as I can tell.

Claude - it looks like we have the same bike!  I'm getting 40mpg, but haven't really been able to take a ride that didn't involve at least a moderate amount of stop lights.  I think I would probably peak at 45.

-Erik

[motorcycleclaude75]

Hey Eric,

Your bike looks closer to the original colour than mine.  I always enjoy seeing other 500's.  There aren't many in my neck of the woods.

Claude