Sunday, April 09, 2017

Improving Fiona's MPG Results

Ever since I got Fiona in working condition, she's exhibited very poor MPG results with each tank full of gas.  There having been other more major things to fix on her, it wasn't until very recently I started troubleshooting why she was getting such poor gas mileage.  I'm talking the low 20s!

Several phone discussions with Richard Winter, who's proven a veritable fount of knowledge, led to the theory that fuel was being lost out the overflow hole on the Bing Carburetors.

This, was after I'd verified no sooty spark plugs or exhaust pipes.  We also eliminated the air filter being too restrictive by putting the muffin top air filters Fiona came with, back on.

So today, Richard had me measure the fuel level remaining in the carburetor fuel bowls and they proved to be to high.  It was 15/32nds on the left bowl and 8/32nds on the right bowl, way too high!  As comparison, the fuel level on Brigitta's fuel bowls (same carburetors as Fiona) was 20/32nds from fuel level to top edge of the fuel bowl!

So I adjusted the tang that the fuel needle rests against on each carburetor float assembly and got it to be 18/32nds between the top edge of the fuel bowl and the fuel level itself,  on both of Fiona's carburetor fuel bowls.

Took Fiona out for a test run and she performed well all the way to 65 mph.  It was now time do run her for a few miles to see if the MPG result was better.

I ran her out to past the Town of Parker and used CO Hwy 83 to get to Castlewood Canyon State Park.  I parked Fiona just south of the entrance and got this pic:

Pikes Peak

Fiona and I proceeded onwards for a few more miles, eventually going past the junction of CO Hwy 83 and Lorraine Road where Pikes Peak provides a great background for photos:

For the above three similar shots, which one do you prefer?  Please let me know in the comments section.

Fiona and I then returned towards Franktown and gassed up.  MPG was 24.98!  Much better than the 21.9 she'd achieved in the previous tank full of gas.  Now, of the kilometers accumulated, 50 km had been done before I made the changes this morning.  Oh, and strong headwinds on the way down to the above shooting location too.

After Franktown, I cruised through the Town of Parker and stopped to check out this "modern art" exhibit near the town center:

We then rode over to the ranching neighborhood where I like to pose my motorcycles with Mount Evans in the background:

The day was so nice and warm, I decided to try for a couple of time lapse videos of the clouds above Mount Evans.  Here they are, spliced together into one video:

After finishing the time-lapse videos, we rode on home.  I stopped for gas even though Fiona had only accumulated 30.5 km since the last fill up.  It took .642 gallons to fill the tank which works out to 31.1 MPG.  So a definite improvement!

More tweaking to be done of course, I hope to get the MPG up into the high 30s, low 40s like Richard Winter's Bural rig.

Update: 15APR17.  Next tankful, which comprised city/dirt/highway driving: 23.98 MPG.  


Scott Seidl said...

I like the bottom pic. If in fact you are losing fuel out an overflow, wouldn't there be evidence of this or could you set something up to verify fuel loss? I'm not familiar with that bikes layout so excuse me if I'm all wet.


redlegsrides said...

Scott Seidl, that's what I thought too but apparently it can happen. More testing to follow....

Learning to Golf said...

I like the bottom picture as well. Something about being closer to the rig for me. MPGs in the high 30s would be great, hope you reach it.

redlegsrides said...

I hope so too AZ AD, we'll see. Thanks for the feedback.

RichardM said...

Another vote for the last photo. Have you checked if the floats float? That would definitely affect fuel height in the bowls. High fuel level in the bowls would cause it to burn rich which you would see on the plugs. Especially if it was so high as to come out of the overflow...

redlegsrides said...

The floats themselves were fine RichardM, they're NOS from the dealer. Checked fuel bowl level a couple of times during the ride and it stayed at desired level.