r1100rt high idle

[K7GLE]

2000 r1100rt. About 50 miles ago I installed a new O2 sensor and an AF-xied, set at 7. (Also replaced FIs with 4-nozzle R12XX style and had the HES wires refurbished about 100 miles ago but I think those are red herrings.) Pulled & replaced fuse 5 & did the throttle open/shut exercise a couple of times. Valves are slightly slack-fit but uniform. Synched the TBs and rode for a while. Idle was high - nearly 1500 RPM when hot. Screwing both BBS's to lightly snug dropped it to 1200 RPM or so.

Removed the TPS and thoroughly cleaned the TBs off the bike (throttle body cleaner, then scrubbed bodies and all orifices with 3:1 water & Dawn soap, blew dry). Butterfly valves have no perceivable rattle/play/looseness, but do not close completely fluid/air-tight...are they supposed to?

Reinstalled the TBs. Reinstalled the TPS unit. Original setting on TPS was 340 mV. I re-set it to 375 but idle was still high, so reduced it to 340 again which dropped the idle a little.

Set throttle cables with 1 - 2 mm slack (using "tighten left side until TPS budges, then back off 1 turn" method) and synched TBs. Now idles at 1100 - 1200 RPM with BBSs both lightly snug. Pushing butterflies closed (rather forcefully) at idle drops the idle...I haven't checked the ability to set the BBSs for proper idle with both butterflies pushed closed due to insufficient hands and no assistant.

Maybe BBS O-rings? Can't get the rings w/o ordering new BBS's and local bike shop had only one, so I tried to find replacements at the hardware store - all were too thick in cross-section to fit regularly (but when screwed in once to test did not reduce idle any).

I'm at a bit of a loss, and am tempted to ride it as-is until it gets enough worse to diagnose.

 

[BC1100S]

Seeing as no one else is chiming in, here's a WAG (wild assed guess)...

Could it be an air leak? Clamps tight and sealing on the TBs where they plug into the manifolds? Are the plugs installed (and in good condition) on the balance tubes under the throttle body?

 

[K7GLE]

BC1100S: Thanks - I did check for air leaks (spraying starter fluid around TB-to-manifold, fuel line, and intake-to-TB interfaces, and BBSs) both before and after TB cleanings.

The only thing that has made any difference is semi-aggressively pushing the tops of the throttle butterflies to close them off (with BBSs seated, remember), so I'll ask again: should the butterflies be completely airtight-closed at idle? If I put my thumb over the intake side of the idle circuit orifice (= BBS screwed in all the way) should the engine stall?

 

[roger 04 rt]

Normally the BBS is a couple turns and and the butterfly is seated on the stop. On the stop the butterfly is open about 0.3 degrees.

Since you have to push the butterflys to get them on the stops, something is hanging them up.

 

[K7GLE]

Since you have to push the butterflys to get them on the stops, something is hanging them up.

Thanks. (Sorry for the late response - I've been out of town for a few days. Powell's City of Books in Portland ROCKS!)

The butterflies are seated on the stops. When I push I'm (gently) warping the upper half so it closes air-tight rather than allowing the microscopic gap.

I obviously have a minor air leak somewhere...Idle is about 1250 with BBSs seated. I've renewed and lightly greased all the o-rings and checked all connections with starter fluid, with no joy.

I hate to reinstall the Tupperware because I'll certainly think afterward of something else I should have checked, but I think I'll just button her up and ride until the problem becomes more obvious.

It's also less urgent now that I have learned I won't be able to take the time from work for a big ride this year.

 

[roger 04 rt]

When the TB butterflys are on the stops they are only open 0.3 degrees. Based on your symptoms (that you have a high idle with the BBS closed) it sounds like someone performed a zero=zero which opens the throttle up to 4 degrees (depending on what a particular TPS does below its 250 mV minimum voltage).

If that's the case, the remedy is to reset the TB stops screws by performing a zero=250 mV procedure.

Do you believe there is intact blue paint on you TB stop screws? (That means the paint is continuous and unbroken from the screw to the receiver.)

 

[dieselyoda]

When the TB butterflys are on the stops they are only open 0.3 degrees. Based on your symptoms (that you have a high idle with the BBS closed) it sounds like someone performed a zero=zero which opens the throttle up to 4 degrees (depending on what a particular TPS does below its 250 mV minimum voltage).

If that's the case, the remedy is to reset the TB stops screws by performing a zero=250 mV procedure.

Do you believe there is intact blue paint on you TB stop screws? (That means the paint is continuous and unbroken from the screw to the receiver.)

I think if you can measure the throttle plates and get the angles as described, you should come show me. Generally, to establish throttle plate angle, start at about a 0.005" feeler gauge and work up until to you get a semblance of idle. I have no idea what angle that would be or how to measure.

Regardless or Irregradless or SH, if the stop screws have been messed with, you need to find a starting point.

But after reading your complaint and everything that you have done, my thought was ignition timing. If the advance is high at idle, so is your idle. Could the HES have slipped? Could the pulley have slipped?

 

[roger 04 rt]

I think if you can measure the throttle plates and get the angles as described, you should come show me. Generally, to establish throttle plate angle, start at about a 0.005" feeler gauge and work up until to you get a semblance of idle. I have no idea what angle that would be or how to measure.

Regardless or Irregradless or SH, if the stop screws have been messed with, you need to find a starting point.

But after reading your complaint and everything that you have done, my thought was ignition timing. If the advance is high at idle, so is your idle. Could the HES have slipped? Could the pulley have slipped?

Air is almost always the culprit on these boxers when idle is high, and often the reason is either an air leak or someone has previously performed the notorious zero=zero which opens the throttle plates too much.

It is fairly easy to get the throttle plate open to spec (but only as a last resort per bmw's warnings). The key is that every 90 mV of TPS movement equates to 0.32 degrees of throttle plate movement, for the first 23 degrees of throttle rotation, measuring the sensitive pot (pins 1-4). Here is the outline, which has been used with success, dozens of times:

Simplified Zero=250 mV Procedure
--Loosen all throttle and fast idle cables
--TBs and BBSs must be clean
--Set TB BBSs to 2.5 turns (just a starting point) and make them equal.
--Center and fully close both TB butterfly valves
--Set TPS to 250 mV and lock TPS screws (no further adjustment of TPS required)
--Open left TB and count stop screw turns after contact until TPS reads 340 mV. Lock left stop screw (no further adjustment).
--Set right TB stop screw open same number turns as left.

--Start engine, warm up to at least 3 bars.
--Balance at idle using only right TB stop screw, do not touch BBS. RPM does not matter
--Lock right TB stop screw
--Continue with a normal TB sync.

A key to the procedure is that the TPS isn't specified below 250mV, which is 0 degrees. It is a sensitive measurement but it works.

 

[K7GLE]

But after reading your complaint and everything that you have done, my thought was ignition timing. If the advance is high at idle, so is your idle. Could the HES have slipped? Could the pulley have slipped?

I have not checked timing since rewiring and reinstalling the HES so I'll check that next. I'm certain I got it back in exactly the same orientation, but as you say slipping is always a possibility. The sequencing of the HES replacement and the idle issue do look suspicious.

Roger 04 RT: I checked and the magic blue paint on the throttle position screw appears to be untouched. I sure haven't touched it!

 

[dieselyoda]

There are many reasons for a high idle and since our engines aren't magic or magical or for that matter, terribly different than any other engine, you need to stick with basics.

Sounds like you have eliminated air leaks as a possibility which eliminates 80% of your problem and throttle body body balance and TPS settings have no influence on idle because these engines aren't sophisticated enough to have an air bypass valve or mass air flow sensor.

You confirmed that the cables aren't holding the throttle plates up and you didn't mess with the throttle stops so that leaves timing and over-pressuring the fuel system because your pressure relief failed.

After that, you are grasping at some long straws...............................