Bad Mojo for my K today ... help me think this through...

[G.Kennedy]

OK ... my K had a bad day today.  This bike has never, ever hiccuped ... ever.  Here is how the ride went.

1985 K100RS with 40,000ish

First things first ... I have been swamped lately and my bike has not seen much running time in the last month.  Battery fully charged.  Changed oil, trans fluid and final drive fluid and a quick lube of the final and drive shaft spline two days ago.

Day off today so I figure I'll take it out for a run up in the local mountains.

Bike is running absolutely cherry, has me kicking my self for those searches I occasionally do on CL for R1100RTs.  Perfect ride.

Roll down Malibu Canyon toward the 101 to get a touch of fuel.  Planning on backtracking right back up to Mulhulland to take it all the way North.

Fuel ... Pull away from the pump and shut it down to check a few cell messages.

5 mins later fire up and pull into street.  

Bike sounds like its running on 2cyls.  Clutch, rev .. gets going better ... but kinda funny feeling.  I am thinking maybe the fuel was vaporizing so I just run it a bit.  Back to the twisties .. running good at speed ... Stop sign ... 2 cylinder feeling a horrible sounding ... rev it up ... sounds good again.  Weird

This is when I decide to call it quits and get the bike home.  Freeway ... no problem ... full power 30 mile freeway rip back to Venice.

Exit the freeway ... crappy idle and 2cylinder sound again ... few stop lights and I am home.  Sounding horrible at idle ... great at revs.

Into the garage.  Pull fuel filler cap, cuz it has got to be bad gas right .... looks perfect.  No visible water, to sludge, Pristine.

OK check plugs next.  All look good, nice and tan.  Cylinder 4 plug wire has lots of corrosion , switch it for one I have on the shelf.

Fire it up.  Sounds decent.  It does not seem to have the 2 cylinder floppy sound.  So I think thats cured.  (I have yet to test it on the street so we'll see)

But now whats up????

Here is what is seems to be doing.  Start the bike, high idle ... then down to normal idle.  Seems fine.  Then the idle will drop to about 500, then there is a slight clunk, then the idle ramps up to 900 ... then slowly back to 500ish ... clunk, ramps up to 900.  Running rough.

Weird.  I check for air leaks.  Nothing obvious.  Sounds like the clunk is coming from the alternator.  Can actually feel the clunk happening.  Could I be losing a bearing in the alternator.  Does the alternator kick on and off??  Could it add strain on the motor and slow down the RPM's?  This is not the original alternator.  It is a 50 amp Bosch.  So is not 25yrs old, but not sure of its age.

Wow alot happened there ... is it all inter related of separate gremlins.  I probably need to drain the gas and switch the fuel filter to eliminate that area.  But whats up with the clunking/idle speed.

My trusty K is down but not out ... Whadda ya thinks??

[G.Kennedy]

... or is the clunking I  am hearing just a momentary hesitation thats making the motor clunk ... then the engine revs a little.

This is sounding a lot like a youtube video is gonna be in my future so ya'll can hear it.

[Scott_]

When was the last time you ran some techron in the gas?
Could be a combination of fuel filter and dirty injectors.

[G.Kennedy]

I run Cheveron gas all the time. And the bike was running sweet first thing yesterday.

It there a bypass valve on the fuel filter. If it's clogged, the bypass could be opening and closing causing the erratic idle.

When Napa open heading there for filter and Drygas to remove that from the table.

[frankenduck]

There's no bypass on the fuel filter.  Good idea to install a new one given how much they cost at Napa. (3032)  When you have the old one out try blowing through it to see how clogged it is.

If you suspect bad gas then the best thing to do is siphon all of the old gas out and get any remaining out with paper towels or whatever.  That's a much better approach than additives.  Additives are better for when you plan to put the bike up for a while.

[G.Kennedy]

Yes I am going to drain and clean the tank for sure.  I'll pick up 5 gallons of Cheveron.  The Drygas would to suck up any water which may be sticking down in the injectors.

I hope the fix is this easy.  I have my doubts though.

I'll post up in a few hours with the results and a video if needed.

[Inge K.]

And how about the resistance in the plug wire you did change?

What I have in mind is, one coil feeding two cylinders and
too much unbalance in resistance would give a weaker spark on one cylinder.

Inge K.

[G.Kennedy]

Well  for now ... all signs are pointing to a bad batch of gas.  Surprising as it was a very busy Shell station.

I drained the tank, changed the fuel filter and filled with a couple gallons of Cheveron 91.  It was still running horrible, so I was starting to think what to try next.  I decided to add a 1/2 bottle of Drygas.  Between the auto parts store and home (3 Miles)  it was starting to run better.  I am going to wait until after rush hour and run 1/2 a tank through it tonight on the freeway tonight and see how it responds.


Keeping fingers crossed.