Hey guys, I just got my bike out of the shop, a 1999 Heritage Classic with an EVO engine at 32,500 miles. I'm the second owner, I believe the only work that has been done, is the Vance & Hines Shorty's and the S&S Super E Carb. For the life of me, I just could not get my S&S carburetor dialed in. The shop said my intake was warped. So that was replaced, a new Dyna-S ignition with heavy-duty magnets was installed, and a new petcock.

The bike is running great, probably the best it has ever run since I bought it. The 80cc engine feels strong.

My problem, is I am only getting about 68 MPG, correction 68 miles per tank of gas. I believe that year has a 4.1 gallon tank and from what I read, most people are getting an average of 40 MPG. So that should put me in the 170 miles per tank range. I only use premium gas if that matters. I have not dropped the bowl, but I think he said he installed a 72-main jet and a 29.5-pilot jet (which is what I have always run with). I really would hate to touch the carb since it is now running perfect. I was just wondering if I dropped a jet size, would that help with the gas mileage, without messing with performance? I am assuming that would mean the carb would need to be adjusted, correct?

If you know of anything else to try, I'm all ears.

Thanks

 

Check the color of the spark plugs. I'll bet they are black and sooty from too much fuel. Might wanna try 280/285 and 70 jets. Look up YOST POWER TUBE. THAT will increase mpg and a little more power. 77 XLH, 10:1 cr, mild porting, Andrews R5 (torque monster cams) and baffled drag piped. IF I can ride it "nice" I'll see 50 mpg.

 

carb air vents plugged
fuel level too high
bowl vent blocked
once i inadvertently blocked the bowl vent on a keihin and i had 10mpg loss, hot start and enrich circuit issues.

 

Fill the tank, ride it, fill the tank, divide miles per gallon with a calculator. Do this twice. with a calculator.

 

Check the timing and make sure the VOES is allowing the timing to advance. Check for vacuum leak or grounding problem.

On a side note: an 80cc engine should get 100+ mpg. OTOH an 80cu in EVO normally gets 45 mpg.