I have a stock 03 FXSTB, local mechanic recently replaced OEM vapor petcock with a nonvapor Pingel petcock. My problems begin at highway speeds. When riding on the interstate at 75mph - 80mph the bike begins to hesitate and surge, feels like it gets fuel then starves, gets fuel then straves. With wide open throttle speed will decrease from 80mph to 70mph. When I pull of the highway on to a two lane road or ride on city streets I have no problems with the bike. My local mechenic doesn't seem to have the answer? Looking for any help and ideas.
It's interesting that it started after you replaced the OEM for the Pingel.. OR did it do it before the replacement also..???
I would say it sounds like a venting prob.. At highway speed it's not venting enough to keep up with demand..
In slower traffic it is able to vent enough..
Next time it happens--as it happens-- reach down and un-screw either gas cap..
If that clears it up then you know it a venting prob..
Do you have two gas caps,, the right side being the vented one.?
If so,,most likely you'll just need to replace it.. Hopefully..
My next guess would be a partly obstructed fuel line or float bowl inlet..
__________________ "Fill your hands you son of a bitch"
Rooster Cogburn
I should have stated it happened witht he OEM also. When the shop tested it they said it was bad and replaced with the Pingel as an upgrade. Only one gas cap and it appears to be venting properly. I removed the gas cap and blew inot it to test it (while parked).
At some point this week I was planning on replacing the fuel line and then moving inside the carburetor to clear the problem.
Hey,WNT..before you go any further I highly recommend that you "test" your gas-cap the way frisco suggested...noting that blowing INTO it (from underneath I bet.) is going retro-grade (backwards) and,you want to see what it does on it's own, under "normal" conditions VS the pressure/vacum that YOU create,anyhow.
This may not even be the source of your problem...but, it's probably the most common issue in these cases...and you really don't want to find yourself slapping your forehead (later) over false results of the 1st thing checked,the WRONG way...right !?!
__________________ "If at first you don't succeed, try again...then swear"
Mark Twain
The venting you need for fuel flow is IN not out..
You want to suck on the little vent hole in the center not blow out..
But that is not always going to show if it works in practice..
In-other-words,, it may vent fine to your mouth but not always while running.. That's why you un-screw it when it happens..
And check float level as Ken said..
But now I'm also thinking jetting.. If you actually lose speed at WOT but not actually die from lack of fuel you could be very lean in the main jet or over-all jetting.. OEM carb..???
Let us know..
__________________ "Fill your hands you son of a bitch"
Rooster Cogburn
Good evening,
I think Frisco is correct as usual. Air leak or lean jets.
1. Did the tech plug the vacum that had been operating the petcock ? Since the Pingel doesn`t need it easy to forget. The amount of vacum to operate the stock petcock is small but as rpm goes up so does the problem.
2. Has the tank been painted ? I had one just like this that had paint particles cloging the fuel line and filter.
3. Check plugs after a wot run for lean condition.
The jetting thing occured to me too...especially with ONLY going 80 mph at WOT...which just ain't up to par.
But,I'm thinking that maybe another/seperate issue...because jetting is a fixed-factor VS variable...and we're dealing with what's described as surging..."GETTING fuel THEN starving"..."GETTING fuel THEN starving"...more of a fuel delivery issue like sticky cap vent - blocked lines - low float level - etc...no ????
__________________ "If at first you don't succeed, try again...then swear"
Mark Twain
Hey all, Frisco-Rigid and all. I have stock cards. No performance upgrades and as far as I know the mechainc cleaned and used the stock jets. I will run my first test tomorrow and post the results. Really though, thanks for all the help and I will keep posting until I find the cure.
OK Harley helpers, let me answer Wrightturn questions and post updates. The vacuum was plugged, tank is original, no paint job. Haven’t checked the plugs yet, because it's not a constant problem. On too today's test ride.
Outside temp 90 degrees. Conducted 3, 8-mile test runs on highway at 80mph, no issues, even able to accelerate when ever I wanted with proper roll on abilities. I rode to the local shop and talked to second mechanic and he is baffled, but trying to research and help. On the ride home from the local shop I experienced the same problem, was able to achieve 80 for about 5 miles and then it started losing power again. Unscrewed and pulled the gas cap rode 1 mile and no change. Put gas cap back on and was able to close the throttle then roll on the throttle and it would accelerate a couple of miles an hour and then start hesitating again. Current tech thinks it might have something to do with the electronics. Keep the ideas coming, as I'm willing to look at everything to solve the problem
Highway hesitation 
Linear Mode
