2003 Road King engine swap
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Stage II
Joined: Mar 2022
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From: Washington state
2003 Road King engine swap
Does anyone know if a 103 or 107 engine with a 6 speed transmission will fit into the frame of a 2003 FLHPI? Looking to add a sixth gear to keep up with my buddies on long rides. When cursing at 70+, my '03's rmps seem a bit too high. I'm not sure if the newer engines and transmission will fit my frame. Thanks for the help! Shiny side up!! Peace
HDF Community Team
Joined: Jan 2022
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From: B.C.
Does anyone know if a 103 or 107 engine with a 6 speed transmission will fit into the frame of a 2003 FLHPI? Looking to add a sixth gear to keep up with my buddies on long rides. When cursing at 70+, my '03's rmps seem a bit too high. I'm not sure if the newer engines and transmission will fit my frame. Thanks for the help! Shiny side up!! Peace
Easier to get new buddies.
Ride secondary roads and enjoy the cruise.
If you are riding through Gods country, dont ride like Hell.
Stellar HDF Member
Joined: Nov 2005
Posts: 3,183
Likes: 836
From: KMHT KFMY
Change your rear pulley, noting there is only so far you can go without having to change the belt.
You may lose some "ooomph" off the line ( twist the grip more to compensate) but you'll drop your rev's in 5th gear
You can also go up on the front pulley....
either choice is cheaper than putting a ton of money into a transmission or new engine
You may lose some "ooomph" off the line ( twist the grip more to compensate) but you'll drop your rev's in 5th gear
You can also go up on the front pulley....
either choice is cheaper than putting a ton of money into a transmission or new engine
Road Captain
Joined: Jan 2018
Posts: 668
Likes: 246
From: San Diego, CA.
Change your rear pulley, noting there is only so far you can go without having to change the belt.
You may lose some "ooomph" off the line ( twist the grip more to compensate) but you'll drop your rev's in 5th gear
You can also go up on the front pulley....
either choice is cheaper than putting a ton of money into a transmission or new engine
You may lose some "ooomph" off the line ( twist the grip more to compensate) but you'll drop your rev's in 5th gear
You can also go up on the front pulley....
either choice is cheaper than putting a ton of money into a transmission or new engine
Unless you are coming any where close to redline rpms, I dont know if I would worry about it. My last bike was a 99 Road King, and it would cruise all day long at 75-80, as long as I wanted or cared to hold that speed anyway, as I recall at or below 3500 rpms ..
Your mileage may vary, but, you might be chasing a solution without a problem. 😬
Seasoned HDF Member
Joined: Dec 2005
Posts: 19,894
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From: poway
An 03 is not spinning too many RPM until you get above about 90 mph.
An 07 up tranny won't fit..
An 07 up tranny won't fit..
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Seasoned HDF Member
Joined: Sep 2008
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From: San Diego, CA
FWIW.... My 2003 Heritage can cruise all day at 75-80 with no issues.... doubt I hit 3500 rpm (no tac), it just hums right along
I bought my '03 Heritage new. I used to cruise all over SoCal and make an annual trip to Yosemite.... Freeways around here are 75 in cities and 80+ in the sticks..... I never had a problem with my 95" (big bore kit) Heritage passing cars on the freeway...
The gearing is certainly different, because these days when I switch from my '16 bagger to my '03 Heritage, I will try to shift to 6th gear, on the Heritage's 5 speed trans, when I first hit the freeway.... but it doesn't last long...
I bought my '03 Heritage new. I used to cruise all over SoCal and make an annual trip to Yosemite.... Freeways around here are 75 in cities and 80+ in the sticks..... I never had a problem with my 95" (big bore kit) Heritage passing cars on the freeway...
The gearing is certainly different, because these days when I switch from my '16 bagger to my '03 Heritage, I will try to shift to 6th gear, on the Heritage's 5 speed trans, when I first hit the freeway.... but it doesn't last long...
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Seasoned HDF Member
Joined: Jun 2017
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From: Granville New York
Big bore to 98", headwork and some cams to match. If you still have some money left HD offers a six speed gearset for the 5 speed...just swap out the gearset. Doing those couple things will yield way better results than going through the struggle of trying to bolt in a newer powetrain. Then your buddies will be here asking how to keep up with you.
Seasoned HDF Member
Joined: Dec 2005
Posts: 19,894
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From: poway
Does anyone know if a 103 or 107 engine with a 6 speed transmission will fit into the frame of a 2003 FLHPI? Looking to add a sixth gear to keep up with my buddies on long rides. When cursing at 70+, my '03's rmps seem a bit too high. I'm not sure if the newer engines and transmission will fit my frame. Thanks for the help! Shiny side up!! Peace
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