Get the absolute most out of that very useful start lever.

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CycleRob
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Get the absolute most out of that very useful start lever.

Post by CycleRob »

Now that colder weather is hitting the USA and Europe, starting the OilHead and keeping it running will be more relevant. After reading about hard starting in a few OilHead posts, repeating the start lever adjustment procedure again seems like a good idea as it is likely buried somewhere deep within a very old, unrelated topic name. That start lever is believed by too many riders to be the "choke" or a mixture enrichening lever. Not true. All it does is add just enough throttle for cool/cold/freezing engine starting and keeping it at a fast idle until the lever is slid to the off stop. The Motronic computer knowing the airbox inlet air and oil sensor temps provides the richer EFI mixture, equivalent to activating a carburetor's "choke". Here's a quick and easy way to get the absolute most of that very useful start lever. I had this adjustment in place for 5+ years without any negative results.

The shop manual specifies a freeplay setting for the fast idle lever, but that's not the optimal setting, especially when there is the normal wear in all the individual plastic parts involved. Even with zero cable freeplay some additional start lever movement is needed before a hot engine idle will increase. Try it on your hot engine OilHead and see how much start lever movement is doing nothing. That ineffective additional start lever movement is a waste, so lets adjust almost all of it away. I talking 1,500+ RPM on a freezing engine. To reveal very tiny throttle applications of start lever misadjustment, it is best performed at a very warm or almost hot engine operating temp. Here's how:

1--Grab onto the start lever cable's rubber cover, where it attaches to the left handgrip's switchgear and slide it away, down the cable outer until it's out of the way. That reveals the cable's freeplay adjuster.
2--Loosen the adjuster lock nut, then turn the adjuster the other way a few turns (lengthening the cable outer) until you just feel the freeplay go away. That happens when it gets a little harder to turn.
3--Start the engine and turn the steering to the left and right steering locks. The engine idle should not increase. If it does increase RPMs, go to step 5.
4--If the idle RPM did not increase in step 3, turn the adjuster out so it effectively lengthens the outer cable, until the idle speed just increases. You may also find that one steering stop increases the RPM while the other one does not and that is normal.
5--Slowly reverse the freeplay adjustment until normal idle speed happens while trying both full steering lock stops, then go one turn additional (toward more freeplay) and tighten the locknut. Work the start lever slowly to ensure the idle returns to normal while at each of both the steering stops.
6--Move the hot engine start lever all-the-way to the max stop (step 2). Say WOW when the hot engine RPMs go over 2,400.

What this procedure does is compensate for wear of the fast idle ramps and wear slop inside the throttle cable junction box, located under the battery box.
Image
When adjusted like this procedure says there will be negative freeplay at the start lever, but just enough to prevent the fast idle ramp from actually advancing the throttle. It is a good idea to occasionally try the steering stop positions with the hot engine idling to reveal if a readjustment is needed to eliminate an RPM increase on a clutch out steering lock U-turn. This RPM increase can also happen if something new tugs on the entire length of the start lever cable, so check out its routing as best you can while moving the steering stop-2-stop.

The R1200R and my F800ST only have amazingly consistent, fast acting computer controlled idle control motors, but I do remember having to use that OilHead start lever . . . and when to turn it off.

.
Last edited by CycleRob on Sun May 02, 2021 9:13 pm, edited 1 time in total.
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Re: Get the absolute most out of that very useful start leve

Post by pebmr »

Thank You Rob! Very timely advice since I have never adjusted mine, I'm sure it can use this, and it was 29 degrees this morning on the way out...
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Re: Get the absolute most out of that very useful start leve

Post by towerworker »

Thanks Rob--timely advice. Mine is finally in need of a slight adjustment. Since I'm parked for a few weeks more it will give me a little something to do.

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Re: Get the absolute most out of that very useful start leve

Post by sstein »

Thanks for excellent description. I am sure I am due for this since I get no RPM increase with 1st stop on lever and only like 1400 RPM at lever full pull. I have developed a habit of holding some throttle to keep the idle at like 2000 RPM until the engine settles. This adjustment should cure that. Thanks!
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Re: Get the absolute most out of that very useful start leve

Post by sweatmark »

CycleRob's sage advice is one of the reasons I'm devoted to this message board. Thanks Rob, and glad you're still sharing expertise.
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Re: Get the absolute most out of that very useful start leve

Post by CycleRob »

A maladjusted start lever can cause excess starter motor crank times, stalling after the start and an unnecessary rider annoyance every time the cold engine is started. When it is adjusted right, possible even by a novice wrencher, it enhances the whole riding experience, especially if there is years of (normal) wear on the fast idle ramp working/sliding surfaces.

For riders in warmer climates that in step number 5 "add 1 additional turn in" (toward more freeplay), it may generate too high a step 1 RPM rise -or- the rider may not be comfortable with having it adjusted so "close to the edge" or so far away from the specified setting. In those cases you can add "2 additional turns in" (toward more freeplay) and still get a better cold start RPM rise over the specified BMW setting.

For the benefit of all, I ask that future replies include both the cold and hot engine step 1 start lever RPM's, before and after the freeplay readjustment (4 different RPM readings). It would also be interesting if you mention that it was adjusted to the 1mm BMW spec. Thanks.
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Re: Get the absolute most out of that very useful start leve

Post by Roger 04 rt »

Rob, Really well written procedure, nice job. Getting the free play adjustment right on an R1150 is critical to getting a good fast start. Here are a couple more ideas.

Listening to the engine or watching the RPM gauge is one way to tell if idle speed has increased. For the greatest sensitivity, measure between pins 1 & 4 on the TPS. ANY increase in TPS voltage above the normal setting (for reference, 340 mV) means that the slack is gone.

Another thing I found is that no slack leads to too high a cool idle. I backed off from the factory setting to about 1800 RPM cool, which is about 3.5 degrees TPS angle in the GS-911. Then for a cold start I hold the lever up for 10-15 seconds when starting, then relax it to mid point.
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