Gas tank size (again) and gas mileage

[pokrovsky]

I’m relatively new to this bike and still learning from the great wisdom of this group so forgive me if this has been beaten to death before.

I have a 2003 CD that i was lucky to acquire several month ago.
The bike is nearly mint and in pristine shape with only 4000 miles on the clock. Carbs are freshly cleaned/synced (according to the guy I bought it from) and overall it runs very smooth.
I converted it to a proper Tourer with all factory parts and in addition to that I installed an interstate tank and AutoMeter fuel gauge (stepper motor and custom calibration)

 I finally was able to get a full tank burnt and calibrated the fuel gauge.
Here is the numbers:
- totally dry tank - I was able to put 7.35 gal in it to the brim
- rode 178 miles till I had to switch to reserve
- after 180 miles I was able to put 6.136 gal into the tank (to the brim again)
- that is equal to a little over 29 mpg

What do you think? How does that compare to yours?
I rode pretty aggressively and during these 180 miles had some city traffic and some very high speed stretches (like triple digit speeds for 20-30 miles at a time)

It seems reasonable to me bit I’d like to hear what you guys are seeing as far as gas mileage with your bikes.
I do smell a little bit of gas in the garage after riding it and parking it but I figured it’s ok considering this is a carburared bike and not an EFI like my other bikes.
I do not see any obvious leaks but the smell concerns me a little

Thanks!

Sergei

[MarkT]

Hi Sergei.  MarkT here.  With the green/pearl IS tank.

I have 4 Valks.  Got the first June '97 new from dealer.  Have an IS tank on that one too, installed around 2000.  Have about 250k on these bikes, mixed riding of course.  They all average about 34mpg, mixed riding.  I rarely hit triple digits.  George (blown bobber) actually gets a little better, surprisingly 35-6mpg.  But really not too surprising, I usually keep him 70mph or less and he weighs less, has no shield.  Twist his tail sometimes as it's just so fun to get the high-powered rush.

The Valk can consume prodigious fuel quantities if you twist the wick.  Get over 4,000 rpm and mileage sinks fast.  Or pull a heavy boxy trailer, same thing.  I have measured as low as 17mpg on the Inzane trip to Morgantown WV pulling a Timeout camper. That trip, avg was about 24mpg.  Pulling a Tagalong, avg is about 28.  W/O trailer, again I get about 34 - yields a range of around 330 to the fumes with the nearly 10 gallons on board.  I get better mileage at speed after I went to the Austone Taxi Tire which is larger diameter, drops the revs.  With that tire, 3500rpm yields 85mph indicated.  I can cruise at such speeds and still get around 34mpg.

Your quantities sound about right.  You might find they vary with different stations too.  I've found there can be significant differences in pump accuracies. So I would take their claimed amounts with a bit of salt.

On the gas smell, you could have some leakage.  Carb maintenance might be in order.  Also, with 6 carbs, lots of complexity there.  I've smelled gas from time to time with Deerslayer, and even with Jade.  Though not lately after much work on the fuel system - but not the carbs.  Jade has a belly tank, with a custom install which took some effort to squeeze it in the limited space w/o leaks.  Also, if you might have some varnish sticking floats open or other issues, a periodic dose of Berryman's B12 fuel treatment will help get the fuel system cleaned out.  I like to put in half a can every other month or so, just to keep them clean.  I'm able to run pure gas in Deerslayer and Jade as my local station has midgrade w/o ethanol.  Have to run the corn gas in George however, as he needs premium, being blown and with a Dyna3000 advancing the ignition.  He gets regular doses of B12 also.

[WintrSol]

Mileage sounds about right for the type of riding you described; I get about the same, riding like that. Better on an easy country ride, maybe 32mph.

In addition to all MarkT's comments on fuel smell, there is one possibility he didn't cover. Sometimes when I fill at the station less than 2 miles from home after a longer ride, I get a little fuel smell from the cold gas heating above the hot engine, and venting fumes out the tank cap. If you have a non-CA model, this is a possibility. I'd still check all of the items on his list first, before dismissing them.

[gordonv]

+1

I've had 3 IS now, and most seem to get in the 170 range to reserve. That's also combined speed riding.

My best mileage was on my 88' GW at 55 MPH on a group ride with beginners. I went from 12L/100Miles to 8L/100Miles.

I also had gotten 124 miles to reserve. That was a fun tank of fuel, just seeing what I could do.

[pokrovsky]

Thank you gens for your replies.
Nice reassurance that bike is in good condition.
I'll try to locate a gas station with ethanol free gas which is very rare in Houston area.
Mark, thanks for your pointers too. I did run 2 16oz cans of seafoam through the system (8oz per tank) since acquiring the bike as well as couple of cans of techron. I'll try Berryman's B12 fuel treatment next but it seems that the system is pretty clean, bike idles silky smooth and there is zero hesitation across the entire rpm range all the way to red line.

I think I discovered possible cause of smell: I was inspecting all the hoses that I could visibly inspect without taking bunch of things apart and stumbled across one breather hose on the right side of the bike behind the ignition switch. It's a short vertically pointed 1/2" hose that was disconnected at the top. Perhaps when I was replacing the fuel tank I somehow knocked it off.
Will monitor and see if the smell goes away. It could also affect the mileage as before I replaced the tank with the Interstate one I remember registering closer to 35mpg average

Thanks again for all your help. This is an unbelievable community of enthusiasts!

[pokrovsky]

This is the bugger that was disconnected:

[Willow]

It troubles me when you say, "filled to the brim."  The tank has an overfill tube which will bleed fuel if you fill it as much as you possibly can.  If you get fuel coming out the overfill tube it could leave a gasoline smell, especially if the hose is not connected.

Your fuel use seems a little much.  You should get 190 or more to reserve.

I fill aggressively but I stop somewhere about the bottom of the square vent hole at the top of the fill tube.

[Jess from VA]

I've overfilled and had some vent runoff, but not for a long time.  I still fill right up to the top ring (as long as I have a good slow flow pump) (filling while sitting/standing on the centered-up bike, burping the tank by gently rocking it when nearly full).  I think the extra tall IS tank can be coaxed to take nearly a half gallon more than many folks do.  I regularly get 220 to reserve (and rarely ride like grandma) and think the extra gas in my tank is part of that.  For instance, I do not drop a single fuel (gauge) bar, until over 50 miles on the (reset at fill-up) odometer.  And that's on both my '99 interstates.

[pokrovsky]

I think that hose being disconnected could have caused a slight drop in gas mileage. I will monitor the next tank and see.

Fuel sender unit in the tank should not be called fuel gauge as it's merely an indicator. I calibrated a stepper motor attometer gauge with dry tank and with totally full one (filled to the top ring while bike was in an upright position, burped, etc) so I know it is right but it is very non-linear: first 45-50 miles the needle does not move a notch, then it starts to plummet and by the time I need to kick it in reserve it shows practically empty tank

[RWhitehouse]

Low to mid 30's is pretty par for the course on these bikes. My all time best was actually 42mpg, but that was entirely back road, lower speed riding, like 45-55mph, definitely not typical. I've also seen it as low as about 25 on a stretch holding it 80-85 with a fierce headwind fully loaded. Normal highway cruising- say 75-80 indicated I'm probably 33-34 on average.

As mentioned going to a higher profile car tire provides a bit of a "gearing up" effect, the popular (now discontinued) Austone tire was a 175/80 profile which dropped RPM a bit and seems generally thought to be good for an extra mpg or two.

Messing with timing advance, either by trigger wheels or the "ECT mod", which spoofs the ignition into thinking the engine is cold all the time, and it automatically dials in more advance for cold starting. The IS ignition also runs 2* advance than the std/tourer. I tried a 4* advance wheel on my tourer for maybe 10k miles worth, and ended up putting the stock one back in. Initially I thought mileage was a bit better, but I was hardly scientific about it, and over time really did not notice any consistent improvement. It does change the feel of the throttle a bit in the mid range, maybe a bit more responsive. I noticed it also created a vibration from about 2000-2500rpm while accelerating that wasn't there before.  But the problem I ran into was in hot weather, on longer rides, I'd start getting ping pretty bad in the low RPM, anything more than the slightest acceleration below 2000rpm and it'd start missing and knocking pretty bad. Higher rpm would run fine, seemed symptoms of too much advance to me. I tried using 89 and 91 fuel and this didn't seem to make an appreciable difference. Put the stock timing wheel back in and the problem vanished.

What did help mileage was putting the stock size 35 pilot jets back in, a prior owner had put 38's in, presumably with the Cobra exhaust it has. I was a 1.75 turns with the 38s, went back to the 35's and ended up at 2.75 turns(less would pop on decel). Still ran great, but I have consistently noticed another 5-10 miles to reserve since. The carbs are otherwise completely stock, so is the airbox.

In the Houston area I want to say the Buc-ee's in Katy has ethanol free. Some bucees do, other's dont. The one in Bastrop is one of the (very) few places to get e-free anywhere near Austin. Otherwise the only stations that seem to carry it are "Murphy USA". There's one random one in the parking lot of a Walmart that has e-free in cedar park.

[WintrSol]

Try pure-gas.org for a listing of e-free gas in the area you plan to ride. If you find a station not on their list (or one that is, but no longer sells it), you can submit a change to the list.

[rug_burn]

I had the gas smell in the garage with the bike sitting, so I investigated.  In my case, the first thing that started seeping gas were those little o-rings on the fittings between the carbs.     Unfortunately that required pulling the carb carrier, re-synching the carbs, etc.  I cleaned and rebuilt the carbs, too.
  Those nitrile o-rings have only a ten year shelf life, so now with 22 years on my '97 Tourer, it was time for new o-rings throughout.

[WintrSol]

I had the gas smell in the garage with the bike sitting, so I investigated.  In my case, the first thing that started seeping gas were those little o-rings on the fittings between the carbs.     Unfortunately that required pulling the carb carrier, re-synching the carbs, etc.  I cleaned and rebuilt the carbs, too.
  Those nitrile o-rings have only a ten year shelf life, so now with 22 years on my '97 Tourer, it was time for new o-rings throughout.

I guess I should order a set, if they're still available, for my '98. Not a job to which I'm looking forward.

[98valk]

I had the gas smell in the garage with the bike sitting, so I investigated.  In my case, the first thing that started seeping gas were those little o-rings on the fittings between the carbs.     Unfortunately that required pulling the carb carrier, re-synching the carbs, etc.  I cleaned and rebuilt the carbs, too.
  Those nitrile o-rings have only a ten year shelf life, so now with 22 years on my '97 Tourer, it was time for new o-rings throughout.

tighten the long bolts that hold the carbs together, they can get loose.

don't know where u are getting the ten year self life from.

[pokrovsky]

Just a little follow up:
After putting the breather hose back where it belongs I saw a little improvement in gas mileage and averaged 32.6 mpg from the next tank with similar riding pattern.
Although that did not eliminate the post riding gasoline smell in the garage so next thing for me will be to investigate and see if the carbs are leaky. There are no obvious signs of leaks anywhere I could reach with a flashlight without taking a lot of things apart.
Although the guy I bought the bike from in May this year told me there was a recent carb rebuild / sync job done on the bike I can not be 100% sure it was done perfect so perhaps I should look into doing it again myself? Unless there are some other suggestions from the braintrust on possible sources of gas smell.
If I go carb rebuild route, what's the best rebuild kit and any additional parts I will need to buy to tackle this?

[98valk]

make sure the carb bowl vent tubes are routed correctly.

[Jess from VA]

Alluded to above, sometimes a gas smell is just an old, dried out, flattened gas cap gasket.  This has been the culprit many times here.

There is supposed to be a wide thin Oring that fits over the underside of the hinged cap (there's an old post here with a picture and diameter measurement), and others have just cut a piece of inner tube (or something) and sistered it over the existing gasket.

I do not know if you go to a bike sitting overnight and smell around the cap carefully this can be detected or not.