Fuel Economy

vach wrote:

How is your bike running? If your bike was missing a cylinder or two, i think you would notice... :blink: Your saying the bike gets bad gas milage, not that it's running like it's missing a cylinder.. The bike would run like super crap..:blink:

No it don't, been there, done that.
It will still run 90-100 mph, at least a 82 KZ1000M will, and if you have not ridden it when it has full power you might not even notice. My brother didn't notice the lack of power, he just noticed the gas leaking from the carb when the bike was idling
The bike was new to him and he hadn't ridden it much, plus he don't have a lot of experience riding bikes.

I think Link14 is talking about the diaphram in the petcock itself. If that gets cracked or gets a tiny pinhole it can allow gas to leak through it and suck gas straight to the cylinder it is hooked to. Pull the hose off the petcock and see if it is wet inside. If it is, there is your problem.

This, on the other hand is possible, although the hole in the diaphragm would have to be a little more than tiny.

Post edited by: steell, at: 2007/05/07 09:47

You might notice a cylinder not firing or you might not. I have been riding these things so long, I can usually feel a non-firing cylinder pretty much immediately but then some folks will not. The problem you are having isn't carb related. Carbs are doing their job... putting gas into the combustion chamber. If the cylinder isn't firing, which is what gas coming out the exhaust juncture with the head means, then there are really only two reasons I can think of...

1. no compression
2. no spark (or firing at the wrong time)

Check compression first. Generally, no or low compression is from a bent valve, bad rings or no valve clearance. The valve clearance issue is easiest to check because all you need is a feeler gauge. If you have no clearance, the valve will hang open. If you find that valve clearances are not the issue, other troubleshooting will need to be done. See the article on valve clearances on our website at www.wgcarbs.com under "wg's Tech Stuff Index".

If you find that you have good compression, then the spark is almost certainly the reason for your non-firing. I suspect you should move to the electrical section in a new post at that the point where you have narrowed the issue to no spark or sparking at the wrong time. The possible reasons are many so I won't start troubleshooting spark in this thread...

Ok, my mistake. I've been riding my whole life and I notice anything wrong with my bike or car.. So, on that note.... How about a heat test on the exhaust coming out of the motor.. That should tell you if the cylinder is firing or not. If it is firing it wouldn't be blowin gas..

Awwww.....FUDGE!!! Seriously? Why can't it ever be as easy as just replacing floats at 8 bucks a piece? I'm seriously just gonna drive this thing off of a cliff...

Bicycle Lee wrote:

I'm seriously just gonna drive this thing off of a cliff...

Yeah, here's the trick to that...

Jump off the bike BEFORE you reach the cliff!

:woohoo:

Bicycle Lee wrote:

Awwww.....FUDGE!!! Seriously? Why can't it ever be as easy as just replacing floats at 8 bucks a piece? I'm seriously just gonna drive this thing off of a cliff...

Float needle valves are an easy thing to check, just remove the carb to airbox boots, if you have a vacuum petcock then turn it to prime, otherwise turn it to ON, then just watch the carb intakes to see if fuel runs out.

Now see, that's not that bad

Post edited by: steell, at: 2007/05/07 18:55

Well, I know it isn't that bad...I'm just frustrated at this point...
BUT!!! That said, I pulled the carbs, checked the float valves...they were fine.
Noticed that the vacuum line out the petcock was hooked into the second carb BINGO!!! The same cylinder that was leaking fuel... the petcock was failing for sure...I replaced it, cleaned the spark plugs, and changed the oil which was mostly gas at this point...
Now the thing runs like a brand new bike...
My only concern now is that cylinder one and two seem to be running cooler than three and four....which is strange because 1 and 4 are hooked to one coil and 2 and 3 are hooked to the other...
Haven't had a chance to test the gas mileage yet, but it already runs like new...
Thank you everyone again for the help and advice...you guys are great

How in the world does gas ever get in the oil is my question. Let's assume all 4 of the floats are stuck wide open and the petcock is feeding fuel. What would happen? You'd have 4 overflow tubes below the bike spurting out fuel like there's no tomorrow, but still no gas in the oil. Make sure you check your overflow hoses and make sure they are not plugged. At least that's how all my carbs work. I've never got any gas in the oil in all these years.

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?

It depends mainly on the angle the bike is sitting at, on the sidestand the carb would fill the airbox with gas, on the center stand the gas ran into the cylinders and diluted the oil. This was on a 82 KZ1000M, my brother's bike, others may be different.

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.

Hey guys, still in St. Lucia, Got an extended stay. I had almost the same prob as yours Lee. I had a jumpy motor and exhaust making spitting noises since the fuel didnt burn or ignite till it got in the pipes, and the spark plugs were flooded with fuel, just the culprit spark plug cylinder which was 2, which was on the accelerator pump'line up with you dont have. I rebuilt the pump and I synced the carbs so they all have the same sized opening on the slides and I washed and cleaned the parts. Also too, I got new coils and sparkers and I got new rubber seals in the lower carb sections, in the bowls. Try all that without new coils and it might help, new Orings and check that needle jet and check the spark plugs for your culprit cylinders first!