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Discussion Starter · #1 ·
Hello All,
I always knew the K1200RS has a heavy throttle spring. Any reason why BMW put that in? I don't know what sense that it makes. I check out the throttle springs at the dealer, the new K1200S, and the R series all have lighter throttle springs.
I rode about 200 miles todays in the twisty....not only did my bike got a good workout, my right hand, connected to my shoulder got sore from twisting that dam heavy spring.
Any suggestions on what to do? Can one change it to a weaker spring?

Plastics
99 K1200RS (silver/blue)
 

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Throttle rocker

I installed a throttle rocker. It's a handle on the ritht end of the grip and allows the palm to "twist" the throttle. I also considered installing covers over the gips to give them a larger diameter. There is a way to change the positions of the springs that reduces the tension, it is a difficult and complicated procedure, but check it out for yourself and make your own judgements.

Ron
 

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As Digs posted, the throttle spring mod makes the throttle so comfortable, I can now rest my palm on an open throttle during cruise, to excercise and reduce white knuckle vibes! I seem to remember you can choose how many springs you alter, I went for the full Monty, but check lock to lock that the throttle sliders always hit the bottom stops quickly with a click and there is free play in the cable (else your idle and ECU will suffer bad data feedback)

Before moving the springs, pass a piece of thread round the loop before moving it off the stock stop, just in case the spring wants to move all the way past its intended resting place.

I used a 8" lenth of 1/8 rod (modify a screwdriver) with a V groove notch cut in the end, to hold and manouvre the spring end to the new position.



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Discussion Starter · #6 ·
throttle spring

thanks all,
I do have a throttle rocker which helps a bit.
For for the throttle spring readjustment procedure, that doesn't seem like something I can do myself.. (I can only add gas, adjust tire pressure, check oil/replace)..so I'll have my mechanic take a look soon.

Plastics
 

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plastics said:
Hello All,
I always knew the K1200RS has a heavy throttle spring. Any reason why BMW put that in? I don't know what sense that it makes.
Plastics
99 K1200RS (silver/blue)
The heavy springs are neccessary to return a worn throttle cable, especially when making a tight left hand turn. This apparently bends the cable housing more than it already is. :(

I relaxed all 3 springs on mine a couple of years ago but recently ran into the cable sticking with slow speed tight left hand turns. Twisting the throttle was giving a delayed response. The most aft spring was reconnected and all seems to be working well now. However, a new throttle cable is on order. :)
 

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I also couldn't find the original pics and attachments but here's the link I followed:

http://www.gunsmoke.com/scot/k12/throttle_spring.html

A previous post left me puzzled thinking that others were slackening their springs a full turn to hook into the original stop. This is not the case. The new resting place for the spring end from memory was only about 45 degrees back on my '97. There is a lump of casting sticking out on the throttle body that serves as a second stop.

When you shine a light in there, armed with fishing line and a forked end long screwdriver, it all makes sense.



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You Might Try This

After re-building the entire right handlebar (a long story for another post) my throttle seemed really firm and sluggish. I went back and remove the cable housings from the throttle twist body so I could get a good free end to work with. I then proceeded to soak the living daylights out of the internal cables with Try-Flow. I just dripped the Try-FLow onto the exposed cable and let it run between the cable and the housing. I worked the cables back and forth in the housings set the ends up on the windscreen and let the whole thing set overnight. I repeated this three more times, then reassembled the cables to the throttle housing. The whole throttle now works slicker than slick with a whole lot less force. If I were an inventor and had more time, I would build a set of cable lube ports than could be installed so the cables could be lubbed without disassembly. I think it would help a whole lot. Best of all, your return springs remain unmolested for those left turn returns.

For long distance rides without a lot of twisties, the cruise control really works great to relieve hand fatigue.

Best of luck

Tim
aka cycle gator
'04 K1200RS -- Orient Blue
 

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The "99's are pre=cruise control aren't they? They only have a single cable. That should not be that stiff unless you have a cable or cable routing problem. Do you have barbacks that may be tweaking the cable some?
 

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I've done 1/2 of the the throttle spring relax mod, the rear most spring was not too hard to unclip and re-position. ( I folded up a sturdy paperclip and hooked the end of the spring. ) The front spring looks like a PITA since the cooling fan is pretty much in your way, looks like the rad needs to move to unhook the fan. 1/2 the mod has helped though but I think I do need to lube the cable.
 

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tward said:
The "99's are pre=cruise control aren't they? They only have a single cable. That should not be that stiff unless you have a cable or cable routing problem. Do you have barbacks that may be tweaking the cable some?
tward-- I like your avitar...:D
 

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here ya go ........

tfkelly said:
Coundn't find it in the archive at this site. Would very much like to know how to do this adjustment.
The link from Gunsmoke is here. I coludn't locate Larry's link with pics, but a search on the Archives for Throttle Spring turned up a lot of reading material.

FWIW, all this recent talk of throttle stiffness has me revisiting the possible solutions. Today it was rainy, so I removed the tupperware and started the "experiment". I removed the cruise cable. Totally. I can't remeber who removed the cruise cable first, but it was two or three years ago. I replied that I thought it was a bad idea. Obviously I've had a change of heart. The cable is in the workbench drawer, and a test ride shows no effects on the cruise (which I almost never use, but ...). I also relaxed the center spring. One spring only. For the first time in 4 years our '02 has a "normal" throttle. I should have done this 4 years ago.

As for the fast idle, I'll post next week. We're going to be gone tomorow and it's supposed to rain. I decided the heck with Moditec and GT1, so I backed off the Throttle Adjuster Valve screw by two turns. (If you don't know what that is, it's a BMW Technician Only adjusted part. Whatever. ;) ) On my short, dark, wet test ride everything was fine, but the idle was too high. This was due to the "original" fuel rail screw setting. In my atempt to match it to the Throtle Valve I had it screwed in too far. The quick "garage" adjustment dropped the idle to a smooth t 1100, but another test ride is required to be sure. Monday or Tuesday I'll know if the idle is "fixed".
 

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Tim,
You did two things throttle-tension related; relaxing the center spring and removing the cruise cable. Which do you feel had the most effect? Did you relax the spring the typical 1/4 turn or a full turn?

I'm surprised that removing the cable had no effect on cruise. Since you're in NC, I suspect you were able to test on something other than a flat road, correct? I would think the cruise cable is for reducing throttle (correct me if I'm wrong, please) and would be noticebly missing coming over a rise. From your description, it isn't needed to accomplish this. Keep us updated on what you experience as you have a chance for a few more miles.
 

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Any change to cruise control feel?

If I could get some input from those of you who have relaxed their springs. Does relaxing the throttle spring make the cruise control feel any smoother when it attempts to accelerate? It currently feels like it pulls hard and fast when accelerating. It creates a small jolt when it accelerating.
 

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Cruise Cable Removal

Spinner said:
Tim,
You did two things throttle-tension related; relaxing the center spring and removing the cruise cable. Which do you feel had the most effect? Did you relax the spring the typical 1/4 turn or a full turn?

I'm surprised that removing the cable had no effect on cruise. ..........
Most effect = removal of the cruise cable. Definately. This change made the throttle feel "normal". (i.e. No drag at all!) I relaxed the center spring the 1/4 turn. When I relaxed the forward spring the throttle actually felt too soft, so I put that one back. (The piece of string to hold the spring tab was a great tip from Larry.)

As for the cable removal, this is the cruise cable from the center of the throttle bodies to the throttle grip. It's only function in life that I can assertain is to release the cruise if you purposely roll off the throttle. Since this is a safety feature, I'm not recommending anyone do it - just as no one would recommend plugging a tire or trying to make it from Ft Stockton to Alpine with 1/4 of a tank showing on the gauge. As for the cruise altering speed, that's still a function of the cruise cable from the crusie black box inside the left fairing. That cable, from the cruise box to the front of the throttle rail, is still installed and functional.

The cruise works fine. The throttle feels like it should have all along. I'll know tonight if the idle is correct (with a pic of what I changed to lower the idle).

p.s. Cruise set jolt CURE: This one's easy .... (and it's a completely seperate function not affected by the spring relaxation.)
  • If the cruise sets with a jolt there is too much slack between the throttle cable and cruise cable at the throttle grip.
  • If the cruise goes "off" when you hit a bump the cables are too tight in relation to each other at the throttle grip.
  • Negative factors: Getting the cables as tight as they should be often makes the throttle harder to twist. Here's a way around that. Leave enough cruise cable slack so that the throttle isn't hard to turn (you can feel this when adjusting thte cruise cable). When setting the cruise on the highway, roll on the throttle ever so slightly, then engage. Smoooooth.
    (for yucks, set the cruise coasting downhill. THAT's the jolt were talking about here. Now set the cruise going uphill. THAT's how it ought to feel.)
 
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