Horrible gas mileage...

[ponchopirate]

Okay, so I can't figure this out.  I went for a ride today and had to pull over and flip to reserve after only 86 miles.  So I head to the gas station and fill up my tank.  It only took 2.5 gallons.  So that means my gas mileage is horrible, barely over 30 MPG.  The other confusing thing is that I only used 2.5 gallons before hitting the reserve.  Any thoughts?

[Kerry]

When I divide I get 34.4 mpg.  Still not good....

Are you sure you were down to the REServe level in the tank, and not experiencing high-speed fuel starvation?  I sometimes flip from RES back to ON just to check....

[ponchopirate]

Thanks, I'll check that out.  Any idea what could be causing such poor mileage?

[MR_PINK]

Thanks, I'll check that out. Any idea what could be causing such poor mileage?

Is there black smoke?  Have you checked basic stuff?  Air filter blockage?  Thats pretty poor mileage.  


Btw im in san jose we should go riding sometime, id like to ride out to santa cruz soon.

[70 Cam Guy]

I'm probably thinking too basically here but the first thing I check with poor gas mileage is my tire pressures.  I have seen as low as 100 miles (normally see 150) to reserve on low pressure.  ...yes yes I learned my lesson

I remember you got new carbs recently so I'm assuming your air filter and spark plugs are clean also.

This may be related to your other poor running conditions at full gas tank.  I bet once you diagnose and solve your trouble with that, your mileage should go up

[ponchopirate]

Thanks for the info all.  MR_PINK, PM me if you're going to come to Santa Cruz and we can go for a ride.

[The Buddha]

OK outside issues not withstanding ... like tire pressure or dragging brakes, or slipping clutch, dirty air filter ... the biggest reason for low gas mileage is... floats set too high ... If your bike is doing anything else... like it runs only on prime or some other crap like smell of gas etc...other factors are possible. BTW 2.5 gal from full to reserve... OK has someone swapped out the in tank filter so it is higher now and you actually have more reserve... or bondo ... lots of it in the tank...
Cool.
Srinath.

[ponchopirate]

Thanks for the info.  I had a feeling my float heights were set wrong.  I just bought some clear tubing, so I'll try Kerry's float height check.  Argh, pulling the carbs again.

[ponchopirate]

Hmmmm... checked my floats.  They're fine.  Argh... maybe I'm doing my math wrong.

[MarkusN]

Could it be that you ran into one of the fuel stavation at high RPM problems (Petcock, improperly vented tank)? So that the short break when pulling over and swithching to RES was really all the bike needed to be happy again.

Calculating mileage from one single pit stop is never a good idea, as the "shut off criterion" when filling 'er up is quite unprecise.

[ponchopirate]

The fuel starvation problem is starting to sound like the most likely cause.  I think I might top off my tank and just ride around with my gas can so I can see how far I can get.  Also, I generally doing around-town driving and keep the bike in the 5k RPM range... so that probably doesn't help.

[octane]

Get one of these...120 miles per gallon!