Extended High Idle

[slmjim]

...it applies a little bit of pressure to the moving parts of the throttle body to open the throttle a wee bit. It applies this pressure to exactly the same mechanism that the throttle twist-grip operates on.

Michael

The linkage attached to the SE Thermal Valve only acts upon the starter valves. It has no influence on the position of the the throttle butterfly plates at all.

Good Ridin'
slmjim

 

[gsforster]

My high idle was at about 1800 RPM for up to a minute or so with the stock ECM; with the unit I replaced the stock ECM with, the fast idle is about 1350 or so for no more than a minute.

I would suspect this is due to a slightly different fuel map in replacement ecm. The wax pellet on the 1300 actuates the starter valves, 3 of which are adjustable, #1 being preset and is the baseline that the others are adjusted to. The throttle cable mechanism in no way has anything to do with the idle speed/fast idle speed. When the wax pellet is cold, the plunger retracts and pulls the mechanism that operates the starter air bypass valves in the throttle bodies. The ecm knows how much bypass air is being allowed into the engine not by throttle movement but by the map sensor signal and how it changes when bypass air changes. It used this info on cold start to calculate fuel quantity for that given amount of air bypass (along with the coolant temp sensor). The replacement ecm may have a different map which changes fuel amount it delivers during cold start (maybe richer, as you mentioned the cold start idle was lower).

 

[CYYJ]

The linkage attached to the SE Thermal Valve only acts upon the starter valves. It has no influence on the position of the the throttle butterfly plates at all.

Jim, GSForster: you are correct, I apologize for the error. I was going from memory, having removed the throttle bodies (once only) back in December. The wax assembly acts on the starter valve mechanism, not on the main throttle control mechanism.

I have corrected the error in my earlier post.

Michael

 

[CYYJ]

And the very first thing I would check....does your bike have an aftermarket cruise control installed?

I don't disagree with that, but if the cruise control is properly installed and rigged correctly, it should be innocent. See the lower right of the photo in post #4.

Michael

 

[Igofar]

I was waiting for that Michael
I know you put yours on correctly (pilots do things right, or they fall out of the sky) and you know how much I don't like them because of all the ones I've had come through the garage with FI codes and air leaks due to improper installation. Since the installation on the bike discussed may be suspect, it was just one other cheap/free thing to eliminate from the trouble shooting etc.
(by the way, I like the picture of you in your cockpit @ Michael)

 

[Smallville]

I'm in Michael's camp on this one, the Wax Idle assembly should NOT be changed or adjusted (per the service manual).
What appears to "fix" one problem, will only cause another one. Do Not tamper with the setting. I've had to go in and correct a couple of these that folks messed with.
I would start by checking a few simple things before ripping stuff apart.
Check the T-stat, is it frozen, scraping, or have black paint in the housing?
Check the hoses underneath the smog canister to see if they are clogged up with dirt or melted from the exhaust pipe?
Check the 5 way T, and replace the vacuum lines with new ones, and do a starter valve sync.
And the very first thing I would check....does your bike have an aftermarket cruise control installed?

No cruise control
Thermostat was visually checked when the coolant system was flushed. I pulled the thermo and housing to check for a stuck thermo and fix loose hose clamps.
At that time I flushed all the coolant lines and inspected the 5 way “T”. The 5 way was completely clear. All the vacuum lines are in good condition with no obvious defects.
I’ll look at the evap hoses again to double check. I have not done a starter valve sync on this bike.

 

[CYYJ]

(by the way, I like the picture of you in your cockpit @ Michael)

Thanks Larry, kind of you to say that.

I'm particularly proud of that flight compartment, because I designed it and specified the avionics, the layout, the type-specific software programming, and the human factors considerations. It's the flight compartment of the Series 400 de Havilland (Viking) Twin Otter, which went back into production in 2010. Over 150 have been delivered since then, they all look the same inside.

Series 400 Twin Otter

 

[CYYJ]

Scott:

Sounds like you have ruled out "the usual suspects", so, I suggest you focus on the less obvious causes of the problem.

My first guess would be that something is fouling the rigging down on the bottom of your throttle bodies - in other words, the bottom of the wax assembly is pushing up against a hose or clamp underneath the black rubber heat mat, or an electrical cable, or perhaps even the engine idle speed adjustment cable is bumping up against the mechanism that operates the starter valves.

Things are awfully crowded down there, and there is only one way to lay out all the coolant hoses, Bowden cables, and electrical cables under and directly above the rubber mat to avoid fouling either the starter valve mechanism or the throttle mechanism.

I took my throttle bodies off this past winter to replace coolant hoses, it took me forever (probably 25 hours of work) to get all the cables & hoses correctly routed with no fouling. I must have installed and removed the throttle bodies a dozen times before I got things right... it got to the point where I could install or remove the set of throttle bodies in less than 30 seconds.

Michael

 

[Igofar]

Thanks Larry, kind of you to say that.

I'm particularly proud of that flight compartment, because I designed it and specified the avionics, the layout, the type-specific software programming, and the human factors considerations. It's the flight compartment of the Series 400 de Havilland (Viking) Twin Otter, which went back into production in 2010. Over 150 have been delivered since then, they all look the same inside.

Series 400 Twin Otter

Your awesome!

 

[slmjim]

...the Wax Idle assembly should NOT be changed or adjusted (per the service manual).
What appears to "fix" one problem, will only cause another one. Do Not tamper with the setting. I've had to go in and correct a couple of these that folks messed with.

I get that. I truly do, and respect your experience. But really; when have ST Riders ever not tinkered with forbidden stuff...?
The 4,000 RPM idle was noted when I picked the bike up new, as a zero-mile leftover 2009 I purchased in 2011. The selling dealer is 600+ miles from home. Wife & I 2-upped on her '93 CB750 Nighthawk to pick it up. We then meandered toward home through AR, MO and back home into KY over the next two days. It was a great break-in ride.
While it was cold "idling" at the dealer's service bay I mentioned the excessively-high idle. Guy said "they all do that new". I was skeptical, but accepted delivery anyway & we headed for home.
Over the next year and 3,000 miles it immediately went to 4,000 RPM on every cold start, and stayed there for what seemed far too long. My '03 never did that. Forum research led me to the wax device. After watching it operate with the airbox off a few times I decided that, if I'm careful and document any changes, that I could return it to the original adjustment position if necessary. Three trial & error attempts later I settled on the 1/4 turn CCW that brings cold start up to ~2000 RPM, which then drops to normal idle after 90 seconds or so with ambient air temp @ 45 deg. F. Cold start in warmer weather just results in idle dropping a little sooner. Never had any problems stalling on cold or warm starts.
Just my 2 cents. YMMV.

Good Ridin'
slmjim