Does This seem right

[evostroker]

2018 Fat Bob 114. First Harley I  ever owned that the power was sort of adequate...at least for now. Just wanted to have a little sound, so installed S&S slip ons, and did the stage one flash. I want to keep the Warranty. Mileage has gone from 41 to 48 mpg on the last two tanks. Does this seem right ??. Might be a little lean at light cruise, but does not seem to run any hotter.  Don't have the cash for a dyno tune right now. Think it will do any harm???

[1FSTRK]

You knew the answer before you asked. The stage 1 flash does not match the S&S mufflers and  with a mileage change of about 15% you took a lean EPA tune and made it leaner. You may be getting a little mileage increase from the additional power but you still are lean. It is your investment and only can decide if it is worth hurting but I would put the stock mufflers on until I could afford to do it right if it were mine.

[tomcat64]

we don't have any "flashes" for the M-8's.. even a stage one requires a street tuner,,

[Pirsch Fire Wagon]

we don't have any "flashes" for the M-8's.. even a stage one requires a street tuner,,

Truth!

ANYTHING the Dealer Does (if they're following guidelines) is going to be lean. To many regulations and court settlements!

EVERY set of plugs out of the rear cylinders I've replaced are so lean its surprising, regardless of Tuner (if the Dealer did it). Not their fault.

Almost impossible to identify lean/rich at cruising speed (at least for me). A five Gas Analyzer will let you know within reason.

I tell people do one or the other (intake/exhaust) until you can get a good tuner to get you running right.

[One4Tone]

...look at your sparkplugs....are they the color of a coffee with 2 cream?....check your mufflers are they clean?...no residue?...any pinging?...if all checks out I would think it's all good. If you have not lost power, not overheating you're good to go. don't forget as the motor breaks in your mileage improves...I don't own an M8...but riding Harleys 40 years.

[PoorUB]

I have had three EFI Harleys and none of them have had a ting of brown on the sparkplug, all white for the most part. Reading sparkplugs with no lead and EFI has become a lost art.

[Breeze]

I have had three EFI Harleys and none of them have had a ting of brown on the sparkplug, all white for the most part. Reading sparkplugs with no lead and EFI has become a lost art.

It's so nice to read an accurate opinion of plug reading.