Flex fuel
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Stage II
Joined: May 2024
Posts: 2
Likes: 0
From: Walterboro, SC
Flex fuel
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
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
Seasoned HDF Member
Joined: Aug 2006
Posts: 24,570
Likes: 30,924
From: Pennsylvania
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.
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.
Grand HDF Member
Joined: Aug 2014
Posts: 3,622
Likes: 1,625
From: Eastern Ohio
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
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
Banned
Joined: Jun 2022
Posts: 673
Likes: 411
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.
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.
Last edited by user 7209823083; May 31, 2024 at 06:39 AM.
Seasoned HDF Member
Joined: Mar 2010
Posts: 21,161
Likes: 7,668
From: Poolville
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...
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Joined: Mar 2009
Posts: 24,758
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From: Snow Hill, NC
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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.
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.
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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.
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.
