Fuel Economy

Ron, I understand that you were replying to vach's post, but just so there is no misunderstanding, the KZ1000M that I was talking about has BS34 carbs. The only 650 here has a GPz750 motor in it, with BS34's also

Aside from the KZ1000M that I gave to my brother, the only other 1000 I have had was a 77, and that was a long time ago. So the info I provided may or may not apply, but I thought (and still think) it's worth checking.

well, I just rode twenty miles on about a half gallon of gas. SWEET.
She's idling with no problems; smooth acceleration; very very quick...
So quick in fact that one of my brand new turn signals blew right off!!! HAHAHA:ohmy:

Ok, I don't have my bike here it's out of state.. So let's say it's leaking from the petcock through the vacuum line.. Where is the vacuum lin on the bike? On the upper end on the side of the carb? It would, depending on the leak in the petcock, go right into the motor or airbox? I fixed the petcock and needle and seats, I assumed it was going through the needles. It must have been going through the vacuum line? Gotta be right? ]:blink:

RonKZ650 wrote:

vach wrote:

If the needle valves were worn wouldn't the gas just leak right through the carb into the cylinder block down into the crank case? That's exactly what my bike was doing. Bad petcock and needle valves. Sure some can go out of the overflow tubes but if the needles are bad gas would leak right through the carbs, wouldn't it?

The only way gas can get into the engine or airbox would mean the fuel level in the carburetor would have to be higher than the throat of the carburetor. I just measured a set of KZ650 carburetors. The overflow tube in your float bowl is sitting approx 10mm (1cm) lower than the throat of the carb where gas would have to be to enter the engine. The overflow works just like an overflow drain in a sink or bathtub. When the water gets to the overflow it cannot theoretically ever rise higher so water could be added all day and the tub would never overflow. Same with the carbs. The only way the carbs could flow gas into the engine would be if gas was filling much faster than it was flowing out of the drain for some reason or other and it rised about 10mm above the overflow tube. Very unusual for this to happen as it's really not possible but stranger things have happened so I'm not doubting it, just relaying the facts.[/quote

You're right about that. If it leaked through the vacuum diaphram it would go right in the engine. Never thought about that one. Every vaccum diaphram I've ever had bad just stuck in the open position causing gas to never shut off, but it could definately also go bad in other ways. Good point.

vach wrote:

Ok, I don't have my bike here it's out of state.. So let's say it's leaking from the petcock through the vacuum line.. Where is the vacuum lin on the bike? On the upper end on the side of the carb? It would, depending on the leak in the petcock, go right into the motor or airbox? I fixed the petcock and needle and seats, I assumed it was going through the needles. It must have been going through the vacuum line? Gotta be right? ]:blink:

Yep.

Had that exact problem myself. A split in the diaphram allowed gas to drizzle down the vent, flooding the whole shootin' match. Gas never got into my particular crankcase, but it's possible it could.

One of the symptoms to watch for is extremely rapid fouling of the #3 plug.

If the cylinders don't fire, gas will be sucked into the combustion chambers regardless of overlfow tubes or not. The carbs will do their job if there is vacuum and there will be vacuum if there is no spark and some vacuum if there is low compression; in either case, if the cylinder isn't firing, gas will end up in the oil.