Hey all,

I recently picked up an 04 Springer Softail (carbureted) from an HD dealership on a trade. First ride home it started showing some strange symptoms and I took it back, they are working on it now since I was able to show them the problem in person. I realize it's their job to do the troubleshooting but I want to do some of my own.

Here's what happened, bike starts and runs fine cold, when it's up to operating temp, at idle, it begins to stumble and eventually cuts out and dies. This is only when the bike is hot, and when it is idling. I can gun the throttle at lights to keep it alive, but if I don't it will die at lights.

First time I took it back, they cleaned the carbs and told me that the PO had a really fat jet running in it ( bike has 2-1 aftermarket pipe). Even if this thing was running super rich, wouldn't it always run like s***? Why would the symptoms show up after it was warm? In my head this seems like a fuel delivery issue, and the bike for some reason, when hot isn't getting gas. Maybe the petcock, or the lines?

Any ideas would be great, I'm just chalking this one up to a learning experience that I thankfully don't have to pay for.

 

I’d try resetting the idle. It might be down too low

 

Had a similar, intermittent problem with my 08 softail efi.
I cleaned out the idle air control weeks ago. It seems to have cured the problem (knock wood).

 

Could be fuel delivery...

Peeling gas tank liner, petcock screen, petcock, fuel line... all possible, but would tend to cause issues regardless of engine temp and would limit flow more at high rpm than idle..

Could be carb adjustment (mixture screw/jets)... hopefully the dealer has someone who can tune a CV40 carb, because they are pretty simple, but not all dealers have someone who worked on carbs these days.....

Could be dirty carbs, especially in the low speed jet area....

Based on, "This is only when the bike is hot, and when it is idling. I can gun the throttle at lights to keep it alive, but if I don't it will die at lights."... I would think there is some debris clogging/gumming up the low speed jet, basic adjustment, or worn parts, to include possible bad carb to intake manifold seals.....

You would think these things were checked/fixed when they "cleaned the carbs"..... but obviously something was missed, skipped, or not done right.... more likely, the carb needs a rebuild, not just a cleaning. Carb parts DO wear...

Being it's a 14 year old bike, I would do a complete carb disassembly, cleaning, and then rebuild the carburetor with OEM needle & jets, plus new parts from a rebuild kit like available from CV Performance...

https://cv-performance.com/carbureto...-cv-carburetor

Then you could do a carb tune from scratch which would also let you know if you have the proper jets...

Just FYI... I have an 88" twin Cam w/CV40 carb that has Stage I (hi flow air cleaner & high flow exhaust). I rebuilt it with OEM jets (45/190) and switched to a CVPerformance Velocity needle, drilled/removed the mixture screw cover (an EPA/OEM thing) to be able to adjust it, and the bike runs stellar...!

 

Hattitude, thank you for taking the time to reply, those are the tips I was hoping for.

The guy at the dealer looks like he's in his 60's so I'm guessing he knows his way around a carb. Even for being a young guy, I cut my teeth on an old Keihin butterfly carb that was an absolute b**** to tune and I have a feeling it's related to the jets. If they're going to do it for free, I'll let them. Hard to believe a CV would need a complete rebuild with 20k miles on it though, but I don't doubt you.

The petcock seems suspect too, it's one of the vacuum operated ones and it seems to run best on RESERVE, seems odd to me. I am thinking it has something to do with that really fat jet though, because the fuel lines look clean and they still have all the heat wrap on them too.

 

Just FYI... The Keihin CV40 is a much better carb, and easier to work on & tune, than the Keihin Butterfly carb..

It's not the mileage on the carb, but the age.... Being low mileage, there was plenty of time for varnish and other bad gas demons to hurt the interior parts...... plus....... o-rings, gaskets, and the diaphragm get dried out and brittle with age... Additionally you have no idea what the prior owner did to it.. from changing jets, needle, and doing some of the diaphragm drilling (bad) hop up tricks... That's why I rebuilt mine, put it back to OEM, and then as I tuned it and tried to dial it in, I let the carb (how the engine was responding to the tuning) tell me what it needed....

As for that petcock, I forgot all about that. It was one of the first things I removed on my '01 carbed bike... I capped the vacuum port on the carb and went with a pingel petcock...

Good luck with the repair.... that CV40, in my opinion, is underrated... Once dialed in that bike should run really well....

 

Update: Got the bike back tonight, went for a dealer ride with about 30 other riders. Bike ran fine for maybe the first 10 minutes (today was hot 90+), then noticed a stumble in traffic. Once we really started moving the bike ran well, but every time I get down to idle, she stumbles and cuts out. Turned around and took it back, this is the third time now, mechanic said he put a smaller jet in it, I'm starting to think this isnt carb related.

Something is failing when this thing is hot, coil? Petcock? Fuel line? Same symptoms, as long as I goose the throttle I can get home, but that literally means blipping it every second at every light.

 

A bad coil will shut down when it gets hot, before it totally fails......

I don't know that the other two would cause this only when hot... but you can check the diaphragm in the petcock for leaks/brittle and the interior of the fuel line for delamination pretty easily...

 

I’d be going through the whole fuel System from tank to carb.

 

Update: Dealer says that they are going to install a clear fuel line on it to see if the gas is boiling and causing the fuel starvation, the other option is to install a free-flow petcock on it to rule out the vacuum one that's currently on it.

I wouldn't think a stock 04 FXSTS fuel line route would cause boiling unless maybe the lines degraded enough over time, they are confident it isn't the carb due to the heat being the common denominator.

Has anyone heard of later model Softails boiling gas?