MPG & What octane gas do you use? - Take 2

[wingnut]

i do get better performance and MPG from the mid range "real gas" that is available around here. I've never heard my 81 ping on any fuel I've fed it so thats not a factor for me. I will use anything in a pinch but always make sure there is non alcohol fuel in the carbs if the bike is going to sit for an extended time. These carbs have been on the bike for 6 years and are due a cleaning. I'll get to it this winter.

[MPittma100]

The Good News

Good luck finding pure gasoline in Roswell. The closest vendor to me is eight miles and it's 89 octane only. 93 octane is available in Suches and at Turners Corner. I have to go to Blairsville for 87. At a rally based in Townsend, TN three weeks ago, I was able to run pure gas all weekend.

Hi Marty,

You are right about that. Probably not a single non-ethanol station in the Roswell-Alpharetta area. I have a shop in Jasper. Found a non-ethanol station just outside of town there on hwy 53. They have mid grade (89) also. That is my only source from here so far. And the good news is that I have plenty of gas cans.

MP

[ExcessiveBiker]

Mpg

The SH has the 750 rear end mod. I used to get 4k at 60-65 with the stock gearing. The H has a 17" rear wheel, so it gives the same numbers as the other bike.
I have never calibrated the tach or the speedo, so their accuracy is based on Yamaha engineering on a 32 year old bike.

ExcessiveBiker

[donebysunday]

Mpg

Have you checked the MPG ?

[motoman]

67octane as the higher octane doesn't go 'bang' soon enough with the low compression ratio of these bikes. As 3Phase has stated: "they'll run fine on kerosene and dead rats."

[motoman]

87octane as the higher octane doesn't go 'bang' soon enough with the low compression ratio of these bikes. As 3Phase has stated: "they'll run fine on kerosene and dead rats."

[Cobia]

On my G

I've always run 87 octane in my G, and even experimented with non-ethanol fuel, but could never get more than 35 mpg. This weekend BikerPhil came over and we/he tore the carbs down, cleaned them, re-assembled them, and put them back in.
On Sunday we went for a 140 mi. ride and I got 40.26 mpg !!!
Big difference.
Due to previous bad experiences where the wire clips on the top of the float needles hung up on the float tangs and flooded that cylinder, we/he eliminated them and set the stop of the float so they would operate within a proper range. This had become a real headache on my bike, don't know why. Typically it happened in #4 and I would drop the bowl and fix it. But then it happened in #2 so it was time to change things around.

[Pizzaboy]

Octane is Resistance to Combustion. The higher the octane, the less tendency to burn. High compression Engines need more octane, because the Higher the compression, The easier the ignition. Think Diesel....Diesel have so much compression they do not even need spark. Ever heard an old car with high compression "diesel" on todays fuels. Hell even my Harley does on occasion.

I dont get why Harley's get so great of millage. My sportster is a Hot rod, 83 rwhp. and I never get less than 50 mpg and often upwards of 55 mpg.

I still dont have my Yamaha Running. But I did find a broken wire. So looking forward to fixing that and riding my Brand New Used 1100 this spring.

[KA1J]

I've always run 87 octane in my G, and even experimented with non-ethanol fuel, but could never get more than 35 mpg. This weekend BikerPhil came over and we/he tore the carbs down, cleaned them, re-assembled them, and put them back in.
On Sunday we went for a 140 mi. ride and I got 40.26 mpg !!!
Big difference.
Due to previous bad experiences where the wire clips on the top of the float needles hung up on the float tangs and flooded that cylinder, we/he eliminated them and set the stop of the float so they would operate within a proper range. This had become a real headache on my bike, don't know why. Typically it happened in #4 and I would drop the bowl and fix it. But then it happened in #2 so it was time to change things around.

Congrats on figuring out the problem. I was stunned when I went from 34MPG tops to 43 tops & all because of an extreme rebuild where I replaced all the jets with new. In an earlier rebuild I had replaced the throttle shaft seals. The old jets must have been buggered by a PO but now I never get less than 40 unless I'm riding it hard.

Gary

[bikerphil]

On Cobia's bike (80G), we also advanced the timing a few degrees and I'm sure that helped a bit with the MPG's.

[BA80]

If I run 60 - 65 MPH I get 40+ MPG also. I already have noticeable detonation at high rpms in high gear. I'm afraid if I advance the timing it will get worse

[bikerphil]

Greg, I put a colder spark plug (BP7ES) in my SF and it seems to help reduce detonanion a bit , YMMV

[BA80]

I actually thought about doing that a while back and never did.

Thanks Phil, I think I'll give that a shot.

NGK plugs run backwards as far as heat range I believe. The higher the # the colder the plug.

[XS11UFO]

FWIW - when I put the bikes away for the winter I fill up with avgas (I know, not legal - no road taxes paid), but also no crap in the fuel. The carbs are nice and clean in the spring + she REALLY likes avgas! Learned that trick on an Airhead (BMW) forum.

Some of the small airports have self service pumps but you might need a friend at the airport to get access. $4.65 / gal. here and that's cheap.

[jetmechmarty]

Why do you put bikes away for the winter in Palatka?