I have a 1994 Road King with the following performance upgrades and was wondering if it would be harmful to try running flex fuel for the higher octane performance?

1994 EVO
Screaming Eagle High compression heads with SE 10.5:1 Pistons
SE solid roller tappets and adjustable pushrods
SE performance valve spring kit
Mikuni 44mm Flatside carburetor
Crane Fireball 310-2 cam
29 tooth power sprocket

 

Only if you want to. Better read up on what gasoline to use in your bike.

Do not think it was made for flex fuel.

If you do I see a rebuild in the future.

Oh and welcome to the forum.

The official greeting person may be along shortly to give you valuable tips.

 

Higher octane does not equate to more power. I don't know if you could tune a carb bike for flex fuel very easily. Flex fuel is very hard on older rubber lines and seals that weren't intended to come in contact with ethanol.

 

I have seen a few Harleys here run on E85 ethanol mix with good success. The very high octane rating opens up for high compression and aggressive timing, and the engine runs cooler than on gasoline. So there is for sure more power on the table.

Since fuel and ignition requirements are quite different it is much easier to get this to work on a efi engine. Getting a carb correctly jetted and adjusted will take a lot of experimenting.

Running true flex fuel, where you can switch between E85 and gasoline or even run a mix of both requires an engine management system that can adapt to the current fuel mixture, I think the only car manufacturer that truly mastered this was SAAB, may they rest in peace, and that engine management was quite advanced, far beyond anything commercially available for Harleys.

The issues with ethanol being harmful to engine components is way exaggerated. Use viton o-rings, and fuel hose made for E85 and everything is fine. On cars there was issues with ethanol diluting the engine oil due to the need of a very rich mixture during cold starts, creating leak down of alcohol into the crank case. This required more frequent oil changes for cars that were mainly used for short trips, on longer drives the alcohol will evaporate from the oil. I dont think any of these issues are a problem for motorcycles.

 

The general rule of thumb is going 30% over your current jetting for regular gas.. So if you're running say 190 Main you're probably going to have to go somewhere up in the 240 range 250.. sSame would go with the pilot jet.. And I would not attempt without some type of air fuel monitor on the exhaust to get it set properly...

 

Just for fun, here is a dyno graph for a 13:1 compression 100" Twin Cam Fat Boy running on E85, built by Swedish workshop Motospeed:

 

I just pick the highest octane they have at the pump available.

 

i have the flex on my truck and it is not that simple.
there is a sensor where the fuel passes through and that outputs to the ecu quality and adjusts timing and such. as a carry over, it will also effect the knock sensor and timing is altered more. for grins and giggles, i logged using diff fuels and the more radical the diff, the more the trims the ecu had to make.

 

Yeah, the fuel quality sensor method has been used by a lot of car manufacturers, mostly with quite poor result. The SAAB system used lambda sensor signal to monitor afr and interpolated between maps for gas and E85. It worked really well, but unfortunately the business model did not..

 

You'll have to rejet or replace the carb to switch from gas to alcohol. Fuel mileage will suck. Alcohol absorbs moisture and will wreck the fuel system if you aren't riding often. Too much *** pain.