Float level and fuel mileage...

[Bonz]

Now that my 80 SG is running like a champ with carb's rebuilt, sync'd, and timing advance working smooooth, I have not seen any appreciable increase in fuel mileage vs. a few weeks ago when it had old carb parts, non-sync'd carbs and a sticky advance unit. As well, I jetted down to 107.5 mains because of my elevation here at 7000'.

The float height measured a bit low, .875" across the board. Even though the bike starts, idles, runs great, could I just be rich down low with that float height, and that is keeping my gas mileage in the 34-36 mpg range? The bike doesn't bog down when I start out from a stop, either when cold or fully warm, or in between, so it's not loading up.

In all honesty, I would have expected a bit of a gain with all that I did, plus going down a size on the mains.

Any ideas?

[dbeardslee]

Could be your right wrist doing it. I can get upwards of 44 mpg, but only when I'm following someone that keeps my wrist in check. When I'm out by myself I'm almost always around 30 mpg. Riding style has a huge impact on mileage. JAT

[CatatonicBug]

I would not expect much mileage improvement with what you have done. In fact, you are getting pretty good MPG as it is! Remember that riding style makes a HUGE difference with MPG's. I have a Dynojet kit installed, and it helped quite a bit, but if I get throttle-happy, I'm lucky to get 34mpg. However, if I cruise at a steady 55-60mph, I've seen as high as 42mpg.

The float height won't really affect mileage much, unless you're running really lean (which you're not). The float height comes into effect at/over 2500 RPM, and will affect the fuel/air mixture at the mid/high range. Check your plugs after a long road trip (it takes a couple hundred miles of consistant riding, under load, to change the plug color) and that will tell you if your float heights are right or not. Look for a nice toasted marshmallow tan on the plugs to indicate the floats are happy.

[Bonz]

I'm pretty restrained with the right wrist, at least as it relates to cruising around for commuting. I am running at 75-80 mph though on the Interstate for 28 miles of my 34 mile round trip commute. Now that you mention it, the best mileage I have gotten to date (41 mpg) was when I went on a 70 mile ride on two lane roads with a friend who has a 97 Harley Springer, and I followed him the whole ride.

What I use as a guide, is all the magazine testers back in the day raved about the fuel economy being in the 42-44 mpg range, and that had to involve a lot of hard riding. Gasoline (10% ethanol around here) has changed since those days too. AND most guys claim to get 34-36 mpg now days, so I'm pretty much in the ballpark.

An interesting note... even on my '01 ZRX 1200 jetted to the moon with pods, full header and exhaust, I pull 47 mpg on the same commute. The ZRX is geared such that I'm at 4,000 rpm at an actual 75 mph, and my SG is sitting at about 5200 rpm at the same actual speed, verified by GPS. Rear wheel HP is 130 and torque is 85 ft/lbs on the ZRX. It's the modern XS, as I have said in my signature line...

[geobiker]

Ethanol Mix

From what I have read, the blended gasolines do not provide the same fuel economy as the unleaded gasoline, prior to the addition of ethanol. I would be interested in anyone who has owned their XS1100 long enough, without any modifications, that they have seen this reported decrease in fuel economy.

The other thing you have to remember is that the original testers were running new machines where everything was spec on the machine. I have noticed that my cars have decreased in fuel economy as they have become "more used".

I like to ride my 1979F somewhat aggressively and I don't think that I have ever seen more than about 35 mpg.

[dbeardslee]

When I first got Betsy in '07 she hadn't seen the light of day in 3 years. When I first got her to fire up I was getting 12 mpg, so I got pretty fixated on mileage. I rolled up my shirt sleeves and started wrenching, with a wary eye on mileage. I still remember the ride when I first got 44 mpg. As soon as I knew she would do it, I immediately quit caring about it - it's just too much fun to turn the throttle . I still check it at every fuel stop, but depending on how I've been riding, as long as it's over 30 I don't worry about it. Week before last I did a fill up and was only getting 25, so I looked her over and found a small leak in the tank. Patched it, and I'm back up to my normal mileage.

Lots of things can affect your mileage - if you're riding into a head wind, or you've got a brake dragging, or your carbs need a sync, or your tire pressure is too low it's going to negatively affect mileage. If you're getting 34-36 consistently (which I agree is pretty darn good), I wouldn't fret unless that number goes down for some unexplained reason - then it's time to see what's what.

[Bonz]

So, then here is a question... Is my 2001 ZRX 1200 THAT much more efficient relative to the XS, that I get at least 10 mpg more out of it even when I'm running up to big speeds more often than the beloved XS that I baby, relatively speaking? Ummm... Obviously or I wouldn't be getting at least 10 mpg more out of it...

In all seriousness though, the main reasons I would say it does so much better are about 1200 rpm less at 75 mph, more torque at idle than the XS makes period, and with that said, the power comes in much lower (torque) whereas the XS needs about 3500 rpm to hit its stride, and I use more relative throttle on the XS to accelerate at a normal rate.

As well, is the shaft drive sapping a lot of efficiency out of the system vs. a chain drive?

[dbeardslee]

Water cooled, chain drive, 10:1 compression ratio, digital ignition with k-trick timing, and stock 4/1 exhaust just to name a few of the Kaw's differences. Doesn't surprise me a bit that you get significantly better mileage on the ZRX. It's pretty much of an apple to oranges comparison. You could always go to fuel injection - I've heard that'll get you BIG mileage improvements. Probably be a big PITA to do the mod, too .

[Bonz]

Yeah, 9:1 compression on the XS, smaller carbs, smaller jets, a bit less displacement. Just seems to me it'd be a lot closer, that's all.

The miracle of technology, eh?

[DiverRay]

As someone who had one of the FIRST XS1100's in the country back in September of '77, I'll say for the record THE MODERN GAS SUCKS!! I was able to get as much as 53mpg, and NEVER less than 40mpg in the late 70's. The "new" fuel really has chopped that much from our bikes. And so you know, I put over 36K miles on the bike before I sold it to a local LEO.
When I got back to the XS, the best I could do was about 42mpg, and a low of 28mpg. This is with the Pacifico fairing on both bikes, although the old one was FULL DRESS, lowers and all!

[cywelchjr]

From what I have read, the blended gasolines do not provide the same fuel economy as the unleaded gasoline, prior to the addition of ethanol. I would be interested in anyone who has owned their XS1100 long enough, without any modifications, that they have seen this reported decrease in fuel economy.

The other thing you have to remember is that the original testers were running new machines where everything was spec on the machine. I have noticed that my cars have decreased in fuel economy as they have become "more used".

I like to ride my 1979F somewhat aggressively and I don't think that I have ever seen more than about 35 mpg.

Well, I have not had my 11 that long, but I have had my 1980 XS400 since about 85. In 85 and such I used to get 53 MPG on a bad day, and saw as high as 56 once or twice. Now, same bike, same tuning, and on a good day I can get about 46, and often it gets as low as 41 or 42. Now I'll admit to having added a few pounds during those years, but by the same token, I know it's not all because of that. So I figure that high 30's is doing well on today's gas, and hitting 40 or above is doing really well.

BTW, I get around 30 in town, and around 36 to 37 on the road. This is with a full vetter touring pack as well. Of course YMMV.

[nikonyamaha]

I think a lot has to do with the quality or type of gas. I use regular gas (87 octane) with no problem and mixed driving gets me around 35-38 mpg.
But on a trip last year, Shell gas (the one that is nitrogen-enriched) was the only "quality" gas on the route and mileage dropped to 30-32mpg. I reasoned this was due to 70mph, head wind, etc. But the bike also became hard to start. Normally it starts at the push of the button but I had to use full choke. When I filled up with Exxon gas the mileage jumped to 41mpg on that leg of the trip with the bike starting as it should. But the next gas stop fill up with Shell and mileage dropped to 30mpg.
After that no Shell gas in my bike and I have had no problem since.

[natemoen]

Thats weird cause some people only use shell cause they usually dont have ethanol in it.

I have not got my bike set up great yet but I am at about 30-32 mpg at this point in its life.

[CatatonicBug]

Thats weird cause some people only use shell cause they usually dont have ethanol in it.

I refuse to use Shell for ANYTHING. If I had a choice between Shell and some unknown misc brand, I'd use the misc brand. I have only had one tank of bad gas in my life, and it came from a Shell station in California. The Ethanol thing is not usually controlled by the brand - it's generally a legal thing. In Missouri and in California, ALL stations have to have 10% ethanol by law. I know in Oklahoma, some stations don't use it, so it must not be a legal thing there.

[ManitoulinLad]

shell clean gas

I know I'm up in Ontario Canada, but when my carbs we all out of wack & was getting lousy gas mileage etc. I had to clean my plugs or the bike wouldn't start (fouled up) if it was not started everyday. Regardless of that I still had to clean them every week just to keep it running. Started to use only Shell gas (lowest grade bronze) & the bike could sit for a few days & still start. Plugs were not as fouled, and didn't have to do the weekly clean. The gas with Shell up here was the cleanest burning. Now my carbs are done up excellently (by Tinman905) & I get 44 mpg & only use shell gas if possible - still the low grade bronze. Just thought I'd throw that out there - Dan