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Discussion Starter #1
I have a toggle switch on my data plate located next to my battery. I'm guessing it was installed by a previous owner. It has two brown wires that leave it and disappear into one of the thick wiring bundles wrapped in black casing. That said I know it's too vague for anyone to speculate on what it might be, but on the toggle switch there are the letters "F" & "O". Just wondering if someone that does a lot of modifications/self add ons might have a clue as to what it might be. I've tried running the bike in both positions and haven't noticed anything.

Thanks

 

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flyinguy68 said:
I have a toggle switch on my data plate located next to my battery. I'm guessing it was installed by a previous owner. It has two brown wires that leave it and disappear into one of the thick wiring bundles wrapped in black casing. That said I know it's too vague for anyone to speculate on what it might be, but on the toggle switch there are the letters "F" & "O". Just wondering if someone that does a lot of modifications/self add ons might have a clue as to what it might be. I've tried running the bike in both positions and haven't noticed anything.

Thanks
I believe some of the older model LTs had a brown wire that could be cut to change the fuel map and improve driveability. I am guessing this was a more conscientous owner who did a more sophisticated wire "cut."
 

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That sounds to me like the brown wire " mod ". It's supposed to come into play
at temps above 85 deg F. with an engine hesitation issue.
(Look in the technical section, FAQ, under performance improvements.)
It looks like the previous owner wanted to be able to switch back & fourth between maps.
 

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That is defiantly the brown wire mod. Cut the brown wire for an alternate fuel map to reduce hesitation in hot weather, but you need to use high octane gas. Install a toggle switch so you can go back and forth. You need to have the engine off to switch. Think of it like economy/performance switch.
 

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How accessible is it?
Is it under the seat or do you have to remove plastic? I think we are guessing blindly. I can't imagine anyone going to the battery area to throw a switch at every fuel stop or every other stop for that matter. We don't know if the brown wires are from the original harness or if they are part of the toggle. Can you pick them up beyond the wrapped casing? Is there anything else alien to the bike? I would not mess with it until I knew more especially since it is not affecting performance.
ride safe :bmw:
 

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Discussion Starter #6
Thanks Folks,

Bill the toggle is under the seat if you look in the upper left hand of the picture you can see the dial for the pre-load, and the purple spray from the rear terminal on the battery.

Assuming this is the brown wire Mod for fuel mapping, Does anyone care to speculate what the letters indicate as to which setting is normal and which is the modified position i.e does the "F" stand for "Factory"?
 

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Close the circuit=stock
Open the circuit=hot wx mod

Best from Tucson
Bob
 

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flyinguy68 said:
Thanks Folks,

Bill the toggle is under the seat if you look in the upper left hand of the picture you can see the dial for the pre-load, and the purple spray from the rear terminal on the battery.

Assuming this is the brown wire Mod for fuel mapping, Does anyone care to speculate what the letters indicate as to which setting is normal and which is the modified position i.e does the "F" stand for "Factory"?
The switch position which connects the brown wire ends (i.e., establishes a path from the Moronic to ground) is the "factory" position. The mod was to cut the wire (breaking the connection to ground) to enable a second ignition timing map in the Moronic (even earlier bikes had a "cat code plug" under the trunk which did the same thing when the little relay-looking box in the plug was removed).

The issue is that as originally delivered, in order to ensure compatibility with poor quality fuel, the Moronic was programmed to retart the ignition timing when the ambient air temp was above 85F, and the rpms were below a certain level (can't remember the number) -- this to avoid the potential for detonation in the cylinders.

The problem was, if you were not aware of this "feature," it could catch you off guard, at the worst moment, such as turning/pulling away from a stop into flowing traffic. While often incorrectly referred to as a "hesitation," what was really happening was that the retarded ignition simply lowered the engine torque output a bit -- enough so what the rider felt was an unexpected "lack" of power. The bike wasn't misfueled or otherwise "hesitating" in the sense of a stumble or lack of combustion, it just wasn't putting out the "normal" level of power the rider expected, which at low rpms could lead to a drop if leaned over.

The "cure" was to snip the brown wire so that the Moronic used a map without the over 85F, low rpm ignition retarding. In theory, this required the used of premium fuel, as the Moronic's programming could no longer "guarantee" that pre-ignition would not happen anywhere in the operating envelope. Not an issue for me, as I always used 93 octane. It is not clear to me that premium was a necessity with the typically good quality U.S. fuels -- there were a number of folks that did not use premium, and I cannot remember anyone saying it gave them a problem in the hot, low rpm range.
 

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I think Mark nailed it.
I was only saying if I was not sure what position "F" and "O" represents I would no mess with it. Also I was wondering how often it had to be used as to why that specific location. And as Mark said a steady diet of 93 octane would take that out of the equation.
ride safe :bmw:
 

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Discussion Starter #10
BecketMa said:
Close the circuit=stock
Open the circuit=hot wx mod

Best from Tucson
Bob
LMAO, Bob, I'm not the sharpest tool in the shed, wondering how I'm supposed to know which way is "open" and which way is "closed" until behold, I noticed on the toggle- "ON, and OFF". :histerica Splendid! Thank you sir!

@ Mark,
Thanks for that explanation of the reason for the MOD. I thought I read in the O.M. that the LT called for premium fuel usage to begin with. If not, I've been spending much more at the pump than I need to.
 

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A small multi tester, DC and AC volts, and resistance is handy to have in a toll box. With that you can measure when a switch is open and when it closes.

I think the one in my tool box is from Radio Shack from the 70s?

Best from Tucson
Bob
 
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