Reaching tank capacity

[RyanG]

So maybe this has been answered before, (I searched but didn't find anything), or maybe it is just a plain stupid question, but does anyone else have problems hitting the tank capacity correctly.  If, according to the manual, the tank capacity is 3.7 gal, and reserve is .87 gallons, I shouldn't hit reserve until I have used 2.83 gallons.  Well last week I rode for approx 90 miles and then had to switch to reserve.  I then rode to 112 miles before I filled up, and then I only added 2.81 gallons.  Now according to the math I still had basically .88 gallons left to use before I ran out of gas, which would have given me an extra 25-30 miles.
Now please feel free to correct me on anything I stated above.  Is there something wrong with my fuel system, or is it normal to not be able to use the entire tank?  I have a trip planned in a few weeks with my 2 brothers-in-law and they can both travel 150 miles before they need to fill up, and I basically can make 100-115 miles if I am conservative.  What gives?  Any thoughts, tips, or help would be greatly appreciated.
Ryan

[Charles S Otwell]

Third gen? you might try pulling the petcock out and checking and clean the screen filter..

[TLRam1]

There is a portion of the capacity that's unusable, roughly between reserve and fill-up is about 2.5 gallons, you Can squeeze more in. Once I hit reserve to empty at 70MPH was 25 miles or about .65 of a gallon at 38 MPG.  

[RyanG]

Yes 3rd gen.  1994 with 20,000 miles.  I have only had it for a few months and have added approx 2000 miles.  Love the ride, and get on average between 35 and 45 mpg, but have to fill up more than the math says I should.  Thanks for the suggestions so far.

[RyanG]

So Terry are you saying that there is approx 3.4 gallons that is actually usable for you, and .3 that is "wasted"??

[TLRam1]

Actually, around 3.15, if I fill, wait fill, wait and get the tank full to the brim, I can get more in.

[LIMagna]

My 96 works out about the same ... I usually hit reserve somewhere in the 90's (usually low 90's) and I'll be damned if I can get 2.5 - 2.6 gallons in there (gas at the very bottom of the internal tank neck) if I hit a station within a few miles of switching. 

[Lurkin]

My reserve hits at about 2.6 gal.  Can't confirm how much of reserve is usable though, most I've put in though is 3.1 gal

[Magnum Magna]

There are a lot of things to take into account for miles per tank.  I understand the math you are doing, but 90 to reserve is my concern.  The only time I was getting 90 at reserve was on trips and we were on the highway going fairly fast.

Counting the teeth on the sprockets can give some insight also why you are getting only 90 to reserve. I don't remember stock numbers.  I had a fairly stock setup and was getting 100 (normal) to 115 (not very often) miles to reserve. So I always felt I could get to a gas station on empty at 130 miles unless going fairly fast then dropping down to 115 miles to empty.

[hootmon]

Ok.. I can't explain all this but here is my experience over the past 6 years..
When I 1st got the bike (stock except it had a 43 rear sprocket), I would hit reserve at about 95-97 miles.
I put in a K&N and it didn't seem to change much, I ran 40-42 MPG consistently unless I was running 80+ long distance.
I Not necessarily in ORDER, but I Put in a 40 rear sprocket, then later drilled a 3/8" hole in each exhaust end and I was getting a pretty consistent 47-51 MPG..
I drilled a 2nd 3/8" hole and upped my main jets to 105's.. I now get a around 42 - 44 MPG (although with the bigger jets, It's even harder to stay out of the throttle!!!

I did make one modification that I like a lot!!!
I drilled a hole in the neck of the gas tank.. I got very tired of eek-ing in the gas a little at a time waiting for the vent to vent the air out so I could add a little more.. (See attached picture)...
By doing this, I fill my tank right up. The hole allows the air behind the neck to come right out and the gas to flow right in behind the neck. I get the tank consistently fuller and at 43 MPG I run out to about 118 miles before reserve just because I start with MORE gas.. To reserve is about 2.7 - 2.8 gallons now where 2.5 to 2.6 before the drilling  of the whole..

CAUTION!!! - IF you do the drilling, You must insure the tank is completely dry and free of fumes, otherwise a spark could set off a bad situation!!

Here is a picture of my drilled Gas Neck.. There is some metal venting pieces, so I had to drill the hole slightly off to the right side, which works well..



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[TLRam1]

I was more referring to real tank capacity verses MPG, MPG will vary depending on driving style, tank volume will always be the same.

[TLRam1]

There are a lot of things to take into account for miles per tank.  I understand the math you are doing, but 90 to reserve is my concern.  The only time I was getting 90 at reserve was on trips and we were on the highway going fairly fast.

Counting the teeth on the sprockets can give some insight also why you are getting only 90 to reserve. I don't remember stock numbers.  I had a fairly stock setup and was getting 100 (normal) to 115 (not very often) miles to reserve. So I always felt I could get to a gas station on empty at 130 miles unless going fairly fast then dropping down to 115 miles to empty.

You have to understand, fairly fast to Robert is 60 mph. 

[Jerry G Turner]

I didn't see a can of seafoam in either one of those pictures of your gas tank Hoot so give yourself a ticket.

[ryjb]

Ryan - good to hear from you again.  I usually put 2.7 gallons in my tank as soon as the reserve turns on for me.  90 miles on one tank is fairly low, although riding style has a lot to do with what your outcome is.  Just for sharts and giggles take it nice and easy for a tank and see if anything improves or changes (if you do this already then forget what I just wrote). Not sure if you remember my trip a few months ago but I averaged 50 MPG.  Longest I went was 120 miles and my reserve never was touched.  Since you have the bike that will get the least mileage from a tank make sure and plan around you for gas stops.  Usually 100 miles or so on a bike is a good chance to stop anyways and stretch.

Here are a few ideas I can think of that may help:

*Check the air pressure in your tires - that can make a big difference.
*Check the condition of your air filter
*Make sure your chain is adjusted accordingly

I am sure there are other things, that is all I can think of right now.

[RyanG]

Thanks so much for the thoughts and advise.  I think that I probably drive more aggressively just because a lot of my trips are short one, ie less than 7 miles.  I have several times made it over 100 miles before hitting reserve, but that is the rare occasion, not the norm.  I know the air filter is getting old and needs to be changed, but was kind of waiting so I can get the K&N plus rejet kit.  We will see what happens.  Thanks again and I will keep everyone posted.