engine stumble #2

[CARVERBOATBOY]

Hi wanted to start a new thread because I’m not sure Gumbal’s problem and mine are the same as he states his is intermittent. What I have is a 86 K100 RT with 75,000 miles, when running at 2000 to 3000 rpm the engine will cut out for a second and then come back to life (not like I’m losing a cylinder more like all four miss a beat). This will happen as long as I try to maintain this rpm range (which unfortunately is 30-40 mph and makes city riding suck like trying to ride a bucking horse) once past this range (or below it) it runs great. Also on the center stand out of gear at the above rpm this situation is present (almost sound like its’ popping back). When at this rpm in city driving with this stumble (miss?) occurring if a light pressure is applied to either of the breaks to make the engine work harder it goes away, throttle has not moved only a load placed on the engine.

The bike is just back form summer service where it had: new plugs, TPI adjusted and cleaned, fuel filter inspected, oil changed etc. I have also just put on new plug wires ($200 out the door) with no change.

Any guesses would be appreciated as I love this bike but I’m at my whit’s end

Thanks Jeff

[sgborgstrom]

Had similar issues with my '91. Solved by replacing the rubber boots between the throttle bodies and the head. Looked good until I poked them and discovered they were delaminating. My guess is the extra air was causing a lean condition that just didn't appear at higher speeds. Bike runs much smoother overall now too.

Steve

[CARVERBOATBOY]

I had cleaned the TPS as suggested in a past post, but I thought I’d do it again just to be sure. When I got the connector off I thought why not try to run it ……………. Guess what it runs the same with it un-hooked as it did when it was connected. Took a vom and check resistance from the 3 connections to each other ……….. nothing, next checked each connection to ground nothing …………… checked for continuity from one to another ………. Nothing ………. Continuity from each to ground …nothing.

Do they just go out completely or am I missing something?

Jeff

[bmwmick]

I had cleaned the TPS as suggested in a past post, but I thought I’d do it again just to be sure. When I got the connector off I thought why not try to run it ……………. Guess what it runs the same with it un-hooked as it did when it was connected. Took a vom and check resistance from the 3 connections to each other ……….. nothing, next checked each connection to ground nothing …………… checked for continuity from one to another ………. Nothing ………. Continuity from each to ground …nothing.

Do they just go out completely or am I missing something?

Jeff

Jeff,
K100's and K1100's are totally different animals for the fuel control. You have an on/off type of switch instead of the rheostat type on the K1100's.
You should have 1 circuit that is clossed at idle and one that is closed at WFO.

[CARVERBOATBOY]

Thanks Mick
I don’t know if this is all my trouble or not but with the TPS un-plugged the bike runs much better, the miss is now almost nonexistent. I have a new one on order when it comes in we'll see if the problem is fixed or back to where it was.

Jeff