79 miles per tank of fuel 83 KZ1100

I really can't believe this... But speedometer is dead on. Even my 2003 ZRX1200 read about 6mph faster than you were going.

I've got a 78 650 and my manual says I have a 3.7 gal tank but I've never been able to pump more than 2.8 gal into it. It seems to have some kind of issue when it gets low with actually using that last gallon. I've been stuck on the side of the road, with the petcock on reserve and I could still hear sloshing around. Anyway, my mileage is about 35mpg and I'm getting about 80 miles now that I have worked out all my engine issues.
I did replace the petcock a year ago, could that cause it to not drain the tank properly? Or maybe it's losing vacuum for some reason?

Yeah, if the pickup tubes are going too deep into the tank... you could be leaving 1.5g of fuel in it and sucking air through the pickup tubes.
I've also been stranded... I one time took the tank off, lifted the front as far as I could and leaned it over as far as possible to the pickup tubes and reconnected it, filling the bowls. Then drove it for almost 2 miles and the engine burbled out, .... did it again and again and again until I limped into gas station 7-8 miles from where I ran out.

The reserve strainer is at the bottom of the tank. I'd pull the petcock and see if some crap is clogging it.
Steve

gcphoto wrote: ........I did replace the petcock a year ago, could that cause it to not drain the tank properly?

Yes. If the petcock you installed is not the same as the original it may not (and it sounds like it is not) have the petcock intake tubes oriented such that they are permitting all the fuel from being drawn from the tank. It sound like both tubes are too high in the tank. If you're getting 35 mpg you should be able to go at least 100 miles before hitting reserve. Once you hit reserve you should be able to go another 20 or so miles before running out of fuel.

If you have the old petcock you may want to remove the new one and compare the length of the intake tubes from the mating surface of the petcock where it contacts the tank. The stock '77 KZ650 petcock has the reserve tube (actually just a hole) flush with the mating surface. Ed

Here is is with the strainers removed.....

For what it's worth, I just got back in from another little 25 mile trip around the back country roads NE of Denver with my wife on the KZ1000a.
We've been doing some evening rides every few days now.
Anyhow, I ran out of gas and hit reserve at exactly 162miles this time.... we were covering a lot of 35mph-55mph roads the last two-three days so nothing super fast or WOT and only an occasional 65mph-75mph on the Interstate Highway.
It took 3.4 gallons of gas to top it off tonight.
Again, assuming my trip OD is off like the speedo.... I'd subtract about 16miles from the OD #s and guess at 146 miles with 3.4 gallons, or
43mpg... seems like that number just keeps popping up all the time on this thing.

As it happens, I had a local shop do this for me last summer because I was slammed at work. So there's a good chance it is not correct. I'll check this out!

76KZ900 wrote: Ok you read the title ...I got 79 miles some highway some city from a full tank. I just bought the bike and it runs really good so no complaints there. No pouring black smoke out of pipe when going down the road. Plugs also look decent. Bike has Pingel petcock that is shut off when not running. Im going to guess its about 4 gallons capacity. When gas guage read e I thought no way ... well its right ask me how I know.. I have not checked jetting in carb although previous owner thought he put 120 mains. Bike has stock carbs with pods and Star header.

99% sure that's where the gas mileage is going. It may run "OK" when you get on it, but you probably have to open the throttle a lot more to get the power. The stock carbs, pipes, needles are all dialed in exactly to get best power and efficiency. Pods usually means it will never run right again, but can be shotgunned in with big enough jets. Never heard of a star header, but I would wager the gas mileage is due to how much farther the throttle has to be open to make the same power as stock.

Ok update.. Carve carbs had 148 jets. It was pretty rich. I put 135 jets in it. Way more responsive. Pilot jets are stock. They do need to be a little bigger as I've got idle screws out pretty far but I'm getting by with them. Mileage went up to 42 mpg when keeping bike at 55mph on highway. As far as header can't say I've ever heard of one either but that's what po told me. Looks like V&H to me.

Apologies for thread hijacking.. this should be a quick answer though.
Hey Ed.. I pulled the petcock and it not the same as the one in your photo. I'm not sure how to remove the strainer without breaking it so I left it on. The main tube in yours is only 1 3/4" where the main tube on mine is 2 3/4"! I suppose this explains why I have to hit reserve so soon. I just bought a petcock on ebay from the same year and model. '78 650D. I'll try that out and see what happens. I guess there's no way of swapping the strainer and tubes? I don't see anything for this model on z1enterprises.com.

Isn't that interesting!??
Mine is about 1 1/2" long.....
If you can't find a shorter one, I'd yank it off and trim the brass to about +1 1/2". Then use good line filters after the selector.