ive been down in iowa all week snd rode a lot of good roads. As i headed back to Montana today, got to blue earth Minnesota where i pumped Shell 91 non ethanol gas. Bike was running great. get back on I 90 and heading to sioux falls around 80 mph.

i start to notice a slight hesitation that appeared randomly.

got to sioux falls and stopped again for fuel as this tank disappeared in 160 miles. Fill up again with 91 non ethanol gas. I also pulled out my trusty fp3 app and checked the fuel tables as the bike was starting to feel a bit warm. it was about 90. i popped back on I 90, cranked it up to around 90 and headed west.

after a few miles, i still feel a slight surging and occassionally it feels like someone just slows the bike down briefly then it accerlates back.

wind was 6 mph, so i know it not wind, as to bad gas, maybe but something feels off. bike just rolled over 23k, miles and has never given s minutes worth of trouble.

96, andrews 48, cam tensioner good at 11k.
ventilator
vertical oil cooler
lowers
oil change 3 k ago, oil is full, trans is full
no issues,

could this be a fuel filter symptom? bad gas cap or just 2 unfortunate tanks of bad gas

bike has zero problem running 100 plus mph, it just surges a bit.

thoughts?

 

Intake leak or maybe really dirty air cleaner?

The simple to check stuff anyway...

 

I did not read what bike you have, but I will go this way:
Clean and tighten battery cable ends
If you don't have OEM spark plugs, install them.
Go to Wally or local parts store and buy a bottle of Heet (only the red bottle) the other option is a bottle of Startron. Install 6 oz's of either and top off the fuel tank and ride it. If it's bad fuel it will clear up with in 50 miles.

 

I would definitely check Air Filter, Fuel filter and for any vacuum leaks. You may have a slight fuel leak in the fuel delivery line within the fuel tank as well. You could check that when looking at the fuel filter. I would also take a good look at the fuel strainer at the pump inlet too.
I almost forgot make sure the vacuum cap is on the port on top of the intake manifold. If that's missing it would create a large vacuum leak.

 

10-4 on the Purge Pipe Rubber cap. The heat cracks them and they slowly create a vacuum leak.
If it still surges might want to put on new manifold gaskets. They're rubber and fatigue due to heat.

 

and the winner is boomer, with a hail mary.

purge pipe cap

so i get up this am around 4, go out, push the bike away from the motel ( super 8) my home away from home.

start it and roll down the hill to a mobil station.

fill up and jump on I 90 to test my roadglide chinese daymakers. which worked remarkably well, as good as the HD branded. $149.00

i run around 85 till i get to al's oasis, stop fill up grab coffee, crank the daymakers down 6 ratchet strokes and roll on towards rapid city. lights were perfect after readjustment.

stop in wall for fuel again, this 30 mpg is getting old quick

get to rapid, stop for some chow while i wait for black hills harley to open.

sitting in the booth, eating my pancakes and see boomers posting. i think you know, i will bet thats it. probably something that simple.

finish eating, pay, get a to go coffee walk out to the bike shine my trusty harbor freight led flashlight and bam, there it is, big crack up the side.

think for a minute, look over at my flex antenna that replaced the eye gouging hd monster aerial, take the rubber cap off the antenna, slip it over the tube where the other one was, start bike, hmm, idles better.

ride up the hill, fill up, head out west on I 90. no surging.

think, just stop and buy the cap. ride past black hills harley, head to wyoming. stop for fuel in moorcraft. 40 mpg. im back.

so, ignored buying this cap all day, ran hard, 810 miles to get home in time for dinner with my family.

temps between noon and four across wyoming and Montana about 101, inacurate temp gauge on bike showed 115.

no further re occurance, 40 mpg consistant from rapid city to outside great falls.

thanks boomer, simple fix, probably would have never thought about it, till you said something.

 

Happy to help. Glad you got the scoot fixed.