Low speed diagnosis help

[roy]

I would appreciate a little help in diagnosing a problem on my 85 K100.

I replaced the throttle cable last week and have had no problems until today. Probably 150 miles since cable replacement with no problems.

Symptoms:
Biked started fine at work and ran smoothly for the first 1 1/2 - 2 miles & then it started to miss when accelerating from idle up to around 2200 - 2500 RPM. At this point it would run fine. Tried accelerating from different RPM's above 2500 and it ran flawlessly. Ride home is 20 miles at highway speeds with two stop signs. At both stops it hesitated and missed almost like timing was retarded some.

1) One suspicion is fuel. I filled the tank on the way to work this morning. Around ten miles from gas station to work. Problem is why would this only effect low speed operation.

2) Would a faulty Throttle Position Sensor cause this? Not sure why this would effect some cylinders more than others.

3) Hall effect: Don't they usually fail when warm and just quit? Tried starting the bike once I was home and it started fine but falter when accelerating under no load. I.e in neutral

Appreciate some advice on where to start looking.

Roy

[PGlaves]

Look for a pinched hose under the tank, or a loose connection. Go back where you were, if the bad gas theory doesn't pan out. I'd add Heet before I did anything else.

[roy]

thanks Paul,
was thinking the same thing about heet. Not sure what connection I could have messed up installing the throttle cables. Will keep you posted when and if i can find the problem.

Roy

[roy]

Part 2:
Ambient temperature this morning was 70 degrees

Tried a half bottle of heet in the tank and when cold bike ran fine. Rode approximately 16 miles on back roads intentionally lugging (shift from 1st to 5th on take off) the engine to see if would miss or stutter with no problems. Tried at this several times and ran flawlessly. Had to sit at a stop sign for minute or two to let traffic clear and then it hesitated and missed at below 2000 RPM's. Had to sit at two more stop lights with the same results.

Sitting in the parking lot at work the idle would hunt between 800 & 1200 RPM. Note: When running properly earlier idle was stable around 1050 RPM. Also could hear/feel the bike missing and working like the timing was off.

Question for the gurus:
Does this sound like the first signs of the Hall Effect sensors going bad?

Other thoughts?

Roy

[98lee]

Just a thought:

If you removed the air filter box when you were replacing your throttle cable, it's possible that the 3" diameter 90 degree hose that connects the airflow meter to the throttle body plenum is cracked or not properly seated.

That would allow unmetered air in and cause low speed issues that could come and go.




:dance :dance :dance

[roy]

Just a thought:

If you removed the air filter box when you were replacing your throttle cable, it's possible that the 3" diameter 90 degree hose that connects the airflow meter to the throttle body plenum is cracked or not properly seated.

That would allow unmetered air in and cause low speed issues that could come and go.




:dance :dance :dance

Yes I removed the tube from the throttle bodies. It was replaced two years ago and is still very soft and pliable. Being short on time and long on projects I have not removed the lowers to triple check this connection nor any of the electrical connections. The hose pushed on easily and the clamp tightened properly so I doubt this is the problem but will hopefully get some time this weekend to start doing some serious diagnosis.

thanks for the thought, it gives me another item to check.

On list so far:

Intake connections.

Mass air flow electrical connector. I did not touch this but just moving the air box cover around may have loosed this connection.

Hoses to fuel pressure regulator. Again didn't touch them intentionally but...

Injector connectors.

Vacuum lines on the TB's along with rubber caps on the test nipples.

Wires under tank. Did some thing get distrubed while feeding the cable through?

Roy