sluggish throttle

[don35414]

I have a "new to me" 88 K100. I have replaced all fluids and checked everything very carefully as I do with any used motorcycle I purchase. The throttle is very sluggish on the return. The gear/chain/cable in the housing has been lubed with a grease like lubricant. Is the proper lube for use there?
I have checked for interference from other sources as per other post on this forum. Any help from more experienced BMW people would be appreciated. Thanks in advance..

[n1hnr941]

Hi Don, I am looking in my CLYMER book for K-bikes, mine is a k1100rs and it says and I quote " Caution Original BMW cables have an internal liner and do not require lubrication. Lubricant oils may cause the liner to swell making cable operation erratic". Then the book reads on how to lubricate non-lined cables. So if you can determine wether the cable is original BMW or not then you can determine what to do. How old is the cable? In good condition, no kinks or sharp bends or crushed. On another thread some one determined that the bike had been dropped on the handlebar end and had damaged the throttle it self. If there are too many unknowns I would vote for changing it and start fresh and with a known cable. Having a sticky throttle is dangerous :wow

[Eric1514]

If you take the cover off of the handle like you have to expose the chain that holds the cable, you can isolate your problem a little more.

That is, hold the wheel with the chain attached down with the fingers of your left hand and with your right hand, try to rotate the wheel the same direction the twist grip would move it (remove the twist grip first). Use your fingernail if you have to and after you've moved it even a 1/4 inch, see if it snaps back. Try a couple times. If it does, the problem is not the cable or the springs on the TB, the problem is the grip and its fitment.

If the wheel won't return, you have a bad/kinked cable.

Good Luck,
Eric

[jdiaz]

Make sure the bike does not have a throttle friction screw! Check the underside of the throttle housing for a silver screw which the previous owner may have added as a "cruise control." That would also show the symptom you are seeing.

If it is the cable (and after 17 years it certainly could be), let the list know and we'll give you a sheet of other stuff to check while you've got the gas tank off. :D

[don35414]

I disassembled the throttle housing and parts at the grip. After a through cleaning and lubing with a light lubricant every thing seems to be ok. I will be removing the gas tank next week to replace a relay that has been acting up.
jdiaz: you mentioned a list of things to check with the tank off. Could you send it to me or direct me to it? Thank you. Don

[jdiaz]

First thing to check is the rubber boot between the airbox and the intake plenum. Make sure it isn't cracking, and if it looks ok, put a screwdriver on the clamps and make sure they are tight. Lotsa airleaks happen here.

Next, inspect the small hose between the plenum and the engine block, just above the left footpeg. This also dries out and cracks quickly, and will leak air.

Change the air filter if you don't know the service history of the bike. The factory filter is fine in this application.

On the top frame member, there is a grounding stud with a bunch of wires going to it. Remove the nut, and clean all traces of corrosion from the frame grounding surface and the ring lugs.

Check the radiator fan and make sure it spins freely. This is an easy time to replace it.

That's probably enough to get you started.