1999 Fatboy Carb
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Stage II
Joined: Jun 2022
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From: Kansas
1999 Fatboy Carb
Hey guys I’m new to the forum, I recently got a 1999 Harley Fatboy. I have the manual and I’ve been trying to diagnose a issue I’m having. My bike runs fine for 10-15 minutes then will shut off will misfire at times but typically happens before the bike is at normal operating temp And it won’t start for 5-10 minutes after shutting off. When it shuts off my lights work everything is still on minus the motor. My oil light comes on. I’ve replaced the coil and plugs but still have the issue, I’ve heard people say replacing the engine temp sensor. As i went through the book and called Harley I do not believe i have a engine temp sensor. The other thing i could think of would be oil sending unit? I am unsure could use some suggestions on what to look for or how to rule out issues.
Seasoned HDF Member
Joined: Sep 2008
Posts: 14,158
Likes: 11,249
From: San Diego, CA
Hey guys I’m new to the forum, I recently got a 1999 Harley Fatboy. I have the manual and I’ve been trying to diagnose a issue I’m having. My bike runs fine for 10-15 minutes then will shut off will misfire at times but typically happens before the bike is at normal operating temp And it won’t start for 5-10 minutes after shutting off. When it shuts off my lights work everything is still on minus the motor. My oil light comes on. I’ve replaced the coil and plugs but still have the issue, I’ve heard people say replacing the engine temp sensor. As i went through the book and called Harley I do not believe i have a engine temp sensor. The other thing i could think of would be oil sending unit? I am unsure could use some suggestions on what to look for or how to rule out issues.
The carb bikes are pretty simple compared to the EFI bikes....
But it all boils down to compression, fuel, and spark are needed to make the engine run...
I think we can assume for now, the compression is good, as it will start after a time delay...
When it dies and won't start, will it still crank over, but not start? Or will it not even crank over at that point...?
When it dies, you need to figure out if it has starved for fuel or it's not getting spark....
Let us know what you find....
Last edited by hattitude; Jun 21, 2022 at 09:47 PM.
Thread Starter
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Stage II
Joined: Jun 2022
Posts: 2
Likes: 0
From: Kansas
When it cuts out the run button acts like it doesn’t work. Doesn’t do anything until the bike cools down no sign of trying to spark or anything and then once it cools down the bike starts and runs fine for the next 10 or so minutes and then the same issue again.
Seasoned HDF Member
Joined: Sep 2008
Posts: 14,158
Likes: 11,249
From: San Diego, CA
Based on your reports, it would seem that when the engine gets hot, it sputters and stalls and won't restart until it cools....
If you are sure you have fuel, then it would suggest a failing electrical part. An electrical component can fail when heated, then function when cooled... It will eventually fail altogether...
A coil can show symptoms like this, but you have replaced the coil and plugs (on an older bike that's new to you, I would also replace the plug wires just as a maintenance item)....
My next suspect part would be the cam position sensor... it takes the place of the crank position sensor in EVOs and the early Twin Cam.. A bad Cam Position Sensor can lead to poor running, the engine stalling, and/or not able to start..
I have never owned or worked on a Twin Cam bike with a cam position sensor, so I have no personal experience with it, nor do I know how to test it... hopefully someone with experience with the cam sensor will chime in...
PS- I also check the battery condition and all battery connections, especially the ground to the frame in front of the battery under the seat, any time I suspect an electrical problem...
If you are sure you have fuel, then it would suggest a failing electrical part. An electrical component can fail when heated, then function when cooled... It will eventually fail altogether...
A coil can show symptoms like this, but you have replaced the coil and plugs (on an older bike that's new to you, I would also replace the plug wires just as a maintenance item)....
My next suspect part would be the cam position sensor... it takes the place of the crank position sensor in EVOs and the early Twin Cam.. A bad Cam Position Sensor can lead to poor running, the engine stalling, and/or not able to start..
I have never owned or worked on a Twin Cam bike with a cam position sensor, so I have no personal experience with it, nor do I know how to test it... hopefully someone with experience with the cam sensor will chime in...
PS- I also check the battery condition and all battery connections, especially the ground to the frame in front of the battery under the seat, any time I suspect an electrical problem...
Last edited by hattitude; Jun 22, 2022 at 08:48 AM.
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