Who Is The Expert On....

gas caps ???
I keep getting a persistent small of gas from my mint original 650C2 in (I believe) the gas cap area. The cap's rubber seal is in perfect condition.
I dismantled the cap but couldn't see any problems except...
I'm not quite sure if the cap internals are supposed to have a check ball of some kind in there or not. Most caps that I've dismantled on other bikes usually have some kind of check valve or ball arrangement. This cap is the oblong/oval shaped one with the lock at the front with the rotating cover over the key slot. The internals have nothing there except for a weird cardboard disc that appears to have been there from new.
Are there any experts out there who can help me with this ???
Are there any suggestions as to where else the gas smell might be coming from ??
All contributions/theories gratefully solicited.

There is a vent in the cap. Not sure how it works as I've never had problems with mine, but air does have to get into the tank as the gas gets used up.
I replaced my rubber seal as I noticed some leakage when I filled it up to the top.

Tanks have to vent both ways in and out. If tank heats up in sun it out gasses. if you don't see gas I would venture you're OK!

I have learned up gas up while on the kick-stand as opposed to the center stand. If the fuel reaches the gas cap while the bike is at rest, it leaks.

How full are you filling your bike?

Qdude: I fill it up fairly close to the top....let's say within 1" with the bike on the centrestand. My problem is the fact that even with the bike stone cold in the morning just sitting on the centrestand I still get the lingering odour of gas around the bike.
None of my other bikes do this, not even my H2 which is a notorious odour-emitter.
I'm stumped. The only other source I can see that MIGHT be the problem is the vent tubes from the carbs.
Hey, maybe I should search for the fume source with a lighted match or lighter ???:laugh: :laugh: :laugh:

Here are some other possible sources of gasoline odor --

Ultra-small unnoticed seepage from float bowl over-flow tubes, evaporating before visible;

Faulty float bowl gasket;

Loose fuel line fitting at petcock, inline filter or carb;

Loose fuel pipe between carbs;

Leak in petcock or petcock fitment into fuel tank;

Loose petcock;

Loose float bowl screw;

Bent ear on floatbowl where it attaches to carb body;

Crack in fuel line;

Clogged floatbowl overflow causing fuel to rise into carb throat and flow back into pod or air box;

If vacuum petcock, faulty diaphram allowing fuel flow through vacuum line into carb throat and running back into pod or air box;

Pin-hole in tank;

Crack in overflow tube inside floatbowl.

With a properly operating manual petcock, sometimes just turning it to off position when parked will help avoid leaking fuel anywhere downstream of the petcock.

Good Luck!