The bike is a '06 Deluxe. 88 incher, with 509 gear drive cams, aftermarket 2-1 exhaust and typical stage 1 air cleaner. Has a "canned tune" from Fuel Moto using the DynoVision gizmo. New coil and plug wires. Runs really nice with nothing else out of the ordinary, although it "seems" to have the sound of an intermittent miss through the pipes at low speed/light throttle, but it can't be felt through the seat. Kinda like a "burble."

It did the following once before, (before the cam change and the FuelMoto tune, plugs and wires, etc)
and then again the other day while riding in the mountains. Nearly identical scenarios.

Ride from home near seal level, get about 50 miles out. Just after a long climb, come to a stop. Upon getting rolling again, a single cough out of the throttle body. Both times at about 5000 feet elevation.

Never has the bike had the "Carb fart" thing when cold. Those two instances are the only times I've experienced the issue.

In both cases, I cut my ride short, not wanted to get stranded in a place where it's hard to get a tow, and in both cases, it ran beautifully on the ride home....roughly 45 miles back.

Any ideas or similar experience?

 

You are describing a lean condition when you refer to "carb fart" so first is to check fuel pressure. Could be a pinhole in the internal pressure line in the fuel tank.
Could be a plugged/restricted fuel filter reducing fuel volume.
Could be a crappy spark plug(s). Stock plugs and wires work best.
Could be a bit of water in the tank getting sucked into the EFI every so often causing the burp.
Could be a seasonal fuel blend change that creates a leaner AFR due to ethanol and/or other additives.
Bob

 

Also, '06 was the year of the 8 degree injector nozzles that would cause low speed running issues on some bikes. There was a service bulletin out on these. They were replaced by 25 degree units. A retune will probably be required with injector change.
See here for info and flow chart-
https://www.rbracing-rsr.com/downloa...jectorswap.pdf

 

Thanks Bob.
All the tank internals were replaced this last December. Both hoses, regulator, filter, regulator housing (billet aluminum rather than the OEM plastic housing). Everything except the fuel pump itself.

While that's no guarantee that there's no defect there, it would prompt me to look elsewhere.

A blob of water....yeah. It was like one of the injectors just didn't squirt one time.
Plugs/wires.....maybe. Fairly new on both counts, but not OEM.

The fuel itself. Maybe.

Here in California, our gasoline has the least amount of actual gasoline than any other state. A good dose of chemical additives, including a dose of ethanol. Typically 10%. Probably not a problem for cars or bikes with active o2 sensors that can compensate for altitude variations. My bike has no O2 sensors.

Thanks jbarr, my bike has the 25° nozzles. I looked when I had the top end freshened up last December. However, because of this issue, and the intermittent "blurbling" at low throttle/light load has me thinking they may need to be replaced. 56,000 miles on the bike.

 

Since you were in the tank for replacements I would DEFINITLEY check fuel pressure.
The rule of thumb is look where the last disassembly/reassembly that was done prior to running issue.
In other words, the fact parts were replaced in no way eliminates the requirement to check pressure. What if the fuel pump is getting tired and not putting out the pressure it is supposed to?
Take it to a shop that can check fuel pressure to eliminate that as a potential issue.
Also it could be that the present fuel formula creates a lean burn that fails to ignite once in a while.
Should really get it to a dyno where all systems can be checked and measured.
Internet diagnosis is never as efficient as a shop with the tools to actually check systems operation.
Bob

 

All good points Bob. Thanks