5.5 or 6.2 injectors on 124 Build.
5.5 or 6.2 injectors on 124 Build.
I’m about to get my bike dynoed. Trying to figure out whether I should bump my injectors to 6.2 from 5.5s. Concerned about the duty cycle being too high on the 5.5s. The bike has a 124 Kit and 64mm throttle body with stock heads.
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Jamie Long / Fuel Moto USA
The USA's Leader V-Twin EFI & Performance www.fuelmotousa.com
Contact 920-423-3309
Email jamie@fuelmotousa.com
Jamie Long / Fuel Moto USA
The USA's Leader V-Twin EFI & Performance www.fuelmotousa.com
Contact 920-423-3309
Email jamie@fuelmotousa.com
HD EFI Guru
Joined: Jan 2008
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Lots of people selling injectors these days and lots of them are not so good. The 5.5's that HD sellsl are a good solid set that do OK up to 140 HP and Torque but they are all done there as you will be in the 95 - 100% DC at or above 5200 RPM. Once you need a bigger injector than those, its a crap shoot as the aftermarket ones we've tested haven't been very good for the over all running of the engine. We have had injectors tested that showed brand new that there was a 12% difference between the two injectors and they were claimed to be flow tested and came with a piece of paper that showed they were supposed to be. Some of the 7.1 flowed less fuel than stock at low pulse width while others flowed more! So just make sure that if you need a bigger injector than the HD 5.5 you make sure and get someone who will except returns and give a full refund if you have troubles.
Last edited by Steve Cole; Feb 24, 2020 at 04:17 PM.
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Joined: Jan 2019
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Lots of people selling injectors these days and lots of them are not so good. The 5.5's that HD sellsl are a good solid set that do OK up to 140 HP and Torque but they are all done there as you will be in the 95 - 100% DC at or above 5200 RPM. Once you need a bigger injector than those, its a crap shoot as the aftermarket ones we've tested haven't been very good for the over all running of the engine. We have had injectors tested that showed brand new that there was a 12% difference between the two injectors and they were claimed to be flow tested and came with a piece of paper that showed they were supposed to be. Some of the 7.1 flowed less fuel than stock at low pulse width while others flowed more! So just make sure that if you need a bigger injector than the HD 5.5 you make sure and get someone who will except returns and give a full refund if you have troubles.
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I just updated my 2017 RGS 107 to the S&S 124 Kit with 475C cams, stock heads, 6.2 Screaming eagle injectors, stock throttle body, and the Power vision Tuner. Fuel moto told me I absolutely needed to upgrade to the 6.2 injectors to support the 124. They indicate problems with those who have stayed down with the 5.5.. I don't have the exact details other than knowing you may starve the bike of fule, causing it to run lean and hot.. The fuel moto guys , which I highly respect, could shed more light on the subjects. My thoughts, if it's torn down, do it now. Good Luck!
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I just updated my 2017 RGS 107 to the S&S 124 Kit with 475C cams, stock heads, 6.2 Screaming eagle injectors, stock throttle body, and the Power vision Tuner. Fuel moto told me I absolutely needed to upgrade to the 6.2 injectors to support the 124. They indicate problems with those who have stayed down with the 5.5.. I don't have the exact details other than knowing you may starve the bike of fule, causing it to run lean and hot.. The fuel moto guys , which I highly respect, could shed more light on the subjects. My thoughts, if it's torn down, do it now. Good Luck!
The stock M8 injectors are 4.38gm and will support in the upper teens for HP. The only current option from H-D is their 5.5gm injectors. In most mild to moderate 124/128" combination's we use 5.5gm injectors, if you are expecting the build to be above about the 150Hp range we would step you up to the next size.
