HarleyTechTalk

Having an issue with rebuild engine sputtering under acceleration around 3500 RPM. I added a new MAP sensor to the rebuild otherwise it was rebuilt the exact same as prior. Would the MAP sensor cause this or should I be looking at fuel pump and filter?

Quote from: TKO on Yesterday at 10:01:16 PMI recently bought a very low mileage 98 Fat Boy. I've put almost 1k on it in the last 3 weeks. The bike runs perfectly... most of the time. 3 or 4 times now, it has momentarily shut off while at speed. It acts like it's out of fuel even though the tanks are full. Then, just as quickly as it die, it fires right back up and runs perfectly for another 150 to 200 miles. Twice now it has died, again, as if it had no fuel or the ignition was shut off but, on these occasions, it did instantly fire right back up. Instead it left me scratching my head on the side of the road. Both times the bike started again after 10 to 25 minutes. The new peacock, new fuel line and carburetor newly cleaned by me leads me to believe this is not a fuel issue. I  think it may be an ignition issue. This bike still has the original electronic ignition. This is the newest road bike I have ever owned and it's the only bike I've ever owned that has an electronic ignition. If it had points, I wouldn't have any questions. Unfortunately, I know absolutely nothing about electronic ignition. Could this be a bad ignition?

Any information would be greatly appreciated.

Thanks

Check the wire coming from the cam sensor and trace it back to the ignition module.
My bike had a metal clamp along the wire that was not installed properly and was pinching the wire. Dealer never found it under warranty and ordered a whole new ignition system.
I fixed the wire and clamp and the stalling and ignition problems went away.
Still have the original replacement parts somewhere in my parts stash!
Worth a check anyway.
Good luck.

There's still some detail left out that would help. Are you losing "everything" including Lights perhaps?

Otherwise it sounds like possible vapour lock (gas cap not venting) but consider heat as well. Examine the main breaker to ensure it's not in a "hot spot" where it's subjected to a heat source (such as the oil tank).

Hello, and Welcome from Connecticut.

Welcome from just across the border (Missouri side)

Pull the points cover, and take a look at the cam position sensor. If it appears to be burnt, gooey, or melted, like this one, that's most likely the culprit. 



Part Number is 32448-95B

I recently bought a very low mileage 98 Fat Boy. I've put almost 1k on it in the last 3 weeks. The bike runs perfectly... most of the time. 3 or 4 times now, it has momentarily shut off while at speed. It acts like it's out of fuel even though the tanks are full. Then, just as quickly as it die, it fires right back up and runs perfectly for another 150 to 200 miles. Twice now it has died, again, as if it had no fuel or the ignition was shut off but, on these occasions, it did instantly fire right back up. Instead it left me scratching my head on the side of the road. Both times the bike started again after 10 to 25 minutes. The new peacock, new fuel line and carburetor newly cleaned by me leads me to believe this is not a fuel issue. I  think it may be an ignition issue. This bike still has the original electronic ignition. This is the newest road bike I have ever owned and it's the only bike I've ever owned that has an electronic ignition. If it had points, I wouldn't have any questions. Unfortunately, I know absolutely nothing about electronic ignition. Could this be a bad ignition?

Any information would be greatly appreciated. 

Thanks 

Hello from Kansas. I just joined earlier this evening. 

Just my opinion on the rods. For what you'll be using the bike for and the motors capabilities, I'd suggest using Darkhorse H-Beam rods. They cost less, and they'll hold up fine, I run them in my 124". Nothing wrong with Carrillo, they make fantastic products. Just that I think they're overkill in all but extreme running motors.

I hope you find the root cause. It sure could be the crank.

So here we are a year and a half later, I'm reviving this thread with an update.

Since the compensator replacement I've been financially struggling and haven't been able to afford to do much investigating, scared of what I might find.  It's been slightly vibrating but rideable, so why mess with it if it's not broke mentality.  I knew the dealership tried to "tune out" the vibration, and this weekend I decided to re-open the case and have the bike dyno tuned.  I figure the retuning would make an improvement or uncover a larger problem.

Unfortunately, it's looking like they uncovered a larger problem.  They found a voltage variation and the vibration increased significantly.  They want to inspect the rotor in case it's lop-sided and hopefully resolve the voltage issue, but they are also going to check the crankshaft runout as well because they're afraid the crankshaft may be "scissored" and separated.  I do feel that this is the core issue, and as expensive as the endeavor is I'm trying to see it as an opportunity for great engine improvements. 

I haven't nailed down much for exactly what improvements I'll be doing, but I'm probably going to be using Dark Horse as it's in the same state that I'm in (the dealership agreed with this is as well) and of course a timken bearing upgrade.  Other than that, depending on cost I might upgrade the connecting rods with lighter weight Carrillo rods.  Much is yet to be decided tho, any recommendations are welcome.