Puzzling Development..running rough

[macman]

85 K100, 17k. Been running perfectly..no issues. After a brief stop last night, began to "stumble" when giving throttle in 1st &2nd gear..finally cleared up enough to get home. Now it starts fine, idles fine, but when applying throttle, wants to sputter and quit. Can feather th ethrottle past the rough spot and revs up fine. No smoke blowing out . Recent air filter at dealers, other than that, no repaires, mods, etc. Any ideas?

[TimTyler]

How much did the dealer charge you to install the air filter?

Sounds like your bike needs a tune-up. You might have bad gas, a bad spark plug, or an air leak.

[bocutter Ed]

Kinda did that to me with a plugged fuel filter.

[Motorhobo]

Kinda did that to me with a plugged fuel filter.

+1 -- sounds like a good place to start and easy, too.

[K75RT Keith]

Sounds like the fuel filter is clogged.  I'd suggest you start by looking in the tank for discoloration and debris when you replace the fuel filter (good aftermarket choices are listed in the Liberry I like the Napa Gold filter). Also check the fuel pump sock filter and the rubber isolator around the pump as they dissolve when exposed to ethanol.   Then check/replace the spark plugs.

[subforry]

Agree with comments about fuel filter, but considering that the air filter was replaced it could be air/fuel mixture problem where the bike is getting too much air and running too lean.
Maybe something was not put back right or has come loose at or around the air box.

[K75RT Keith]

As a dealer installed the air filter, I'd contact them and ask they check their work (at no cost to you).  I'd also just replace the darn fuel filter and then I'd KNOW that isn't the problem and they won't be able to bluff you into spending more bucks for a simple problem.

[richarddacat]

Might as well check for cracked or loose vacuum lines. 17k doesn't seem like many miles to clog a filter unless your fuel was contaminated, may look inside the tank for the obvious. Time would be the cause with the rubber hoses and such.
I also suspect the dealer moved or pinched something or left trash in the air box.

My 87 had a TB screw back out and the caps for the sync hoses cracked in my fingers. This cause my rough running.

Good luck and post back.