TOPIC:

I have a 1978 KZ650B, not sure if it's a B1, B2, etc.

It was in storage for the winter. When I put it in the garage last night and came out to the garage this morning, I smelled gas. Then I remembered, it smells like that pretty much all the time.

There's never been any gas on the floor and there's no visible drips on the engine, though the starter cover is a little stained/discolored from gas. The rubber carb holders were replaced some time ago when I sent the carbs to WiredGeorge; when I got them back from being rebuilt, I replaced them.

I think, but I'm not sure, that I remember the smell going away if I haven't ridden the bike for a few days.

The petcock is not in the PRIME position.

Any ideas?

Gas tank has a pin hole or petcock is leaking past the diagphram o-ring

make sure the float needles are stopping the flow of gas. It could be coming out of the overflow tubes and evaporating before you see it

Thanks for the reply. Wouldn't I see gas (or a stain on the floor?) Or maybe Nickleo is right and it's evaporating.

Gas usually doesn't leave a stain when it lands on concrete. When I accidently left my petcock on PRI last season it was dripping all over the floor overnight (leaving my gas tank almost empty) and had evaporated leaving just a gas smell

You should also check your air box, & make sure its not getting in there ..Pete

Be sure to check oil level in the crank case. If the needle valve is leaking the gas could be running into the cylinders from your carbs and then seeping past your rings into the crank case. Remove the oil fill cap and smell...see if you get the scent of gas in you oil. That would be bad news to run the engine with gassed up oil. Good luck
Ty

When my fuel tank petcock was defective, I routed the carburetor drain tubing to a clear juice container under the bike to collect the leaking gasoline for visual verification of the leak. Cuts way down on the fumes too (just about eliminates the odor).

I would remove the petcock and clean & inspect it. Buff the mating surfaces w brass wool or steel wool, especially where the diaphragm o-ring contacts the petcock body - it needs to be smooth there. If pitted or scratched, you may have to replace it. If the petcock body seems rebuildable, either get a petcock rebuild kit or a diaphragm kit. K&L parts are made in Japan. The stuff may still be available from the dealer.

In the air box? You mean it's leaking backwards through some of the carbs?

Be sure to check oil level in the crank case: This has been going on for several years and so I've changed the old many times. The oil seems ok-- doesn't smell gassy and doesn't seem thinned out. The level in the sight glass on the crank case is usually very stable and constant-- looks low when the engine is running and returns to just above half-way mark with the bike off and on the center stand. Does this mean it's probably not leaking into the cylinders?

Thanks.

Martin:
Great idea to use a jar under the overflow tubes-- I will have to try that.

I think I replaced the petcock some time ago, or rebuilt it. I'll have to inspect it again.

Thanks.

Leaking into the cylinders is a possibility - something to check. The overflow tube in one or more of the carbs bowls could be clogged, so excess fuel has to go elsewhere, either the airbox or the cylinders. The excess fuel could be from a defective petcock or a float needle valve problem. So as suggested, check the airbox & also remove the oil filler cap & sniff for gasoline odor.

To collect the leaking fuel use a juice container w a small opening to cut down on evaporation.
If you use a jar, cover it w a thick cloth.