Cylinder cutting out below at idle goes away 3000rpm

[Learch]

So I got the bike rode it for a week had no issues filled the tank took it to work  which is 32 miles one way and notice that that it didnt want to idle once I got to work . Acts  like its dropping a culinder  ruff idle then smooth .  check fuel pressure low pressure changed regulator still low pressure changed pump bike still won't runn well below 3 grand .used seafoam through the intake and it improved the throttle response.  Drained the  tank and refilled no change ..I cannot figure out what is going on any help would be appreciated thanks.

[The Mighty Gryphon]

Have you checked all the hoses and throttle body bushings for air leaks?  There are threads here that go into that in pretty good detail.  Sounds like that could be the problem.  An air leak leaning out the mixture at low rpm's.

Long shot here, but did you change the fuel filter while you were in there?  I would suspect it of affecting high rpm's more than idle, but as long as you were in there it wouldn't hurt.

[drut]

"Long shot here, but did you change the fuel filter while you were in there?  I would suspect it of affecting high rpm's more than idle, but as long as you were in there it wouldn't hurt."
+1 if you are finding low pressure.When my filter choked bike ran OK at higher revs but rough at low/medium.As already stated intake rubbers well worth checking plus if you haven't already done so a compression check might be a good idea.

[Learch]

Yep. Filter changed before pump. I forgot to mention the bike only has 52,000 miles on it and it's a 92 k75. It was my dad's bike and he sent to me from main.

[Learch]

I don't see a cam sensor or crank sensor having an intermitten failure like this normally they just fail

[Laitch]

I was going to suggest removing the spark plug cover, running the engine in the dark and looking for arcing, but only because it's probably going to be a nice evening where you are; however, checking for air leaks as Mighty Gryphon suggests is straight forward and it's supported by this thread.
http://www.motobrick.com/index.php/topic,4232.msg27865.html#msg27865

[The Mighty Gryphon]

The rubber bits and hoses on your brick are going on 24 years old.  It would not be unusual for one or more to be cracked or split.  With the fuel injection being controlled by the Mass Airflow Sensor(MAS) any air leaks between it and the cylinder will result in a lean idle mix that probably won't ignite.

Opening the throttle and raising the rpm's will cause more air to flow through the MAS vs. the leaks which will increase the fuel being injected and the mixture will get richer and the engine will run better.

There are procedures for checking for leaks.  The easiest is to feed a small amount of propane through a hose connected to an unlit torch to the vicinity of the hoses and throttle body bushings while the engine is idling.  When the propane is hose is near the air leak, the idle will smooth out and speed up as the propane is is sucked in and makes the mixture less lean.

If you do a search on posts about air leaks, you will find that they are not uncommon.  It's a good idea to eliminate them as a problem before getting into more esoteric stuff.

[Learch]

Thanks for the help guys .  These gass thing give me a headache   Give me a Diesel any day no I'll have that licked.

[K1300S]

i did quick exam of my intake hoses....crankcase vent hose has big crack right below the clamp.  a post AFM issue.


new one on order.

[Learch]

That I replaced before anything

[The Mighty Gryphon]

That I replaced before anything

Are you saying that you already checked the rubber stuff?

[Learch]

I did spray carb clean around all that and no change.  The vacuum tube frome the cc to air cleaner was replaced

[Laitch]

I emailed the OP inquiring about the outcome since I was heavily invested in my spark theory. :oldguy:
I receive a gracious response. What it needed to get underway again was injector o-rings, upper and lower throttle body boots, and a throttle body adjustment.