Hello gentlemen, another quick question.Still getting my 85 k100rt tweaked in and having some issues with the throttle,it seems that my throttle has to be manualy pushed off, I was wondering if it has a throttle return spring somewhere? haven't taken the fairing off yet. it seems that it should have one but I haven't located it yet. Would it be down nearer to the engine? Or is it a matter of lubricating the cable? Any help is appreciated.thanks..

Hello down under!
You can put a drop of WD40 on the throttle and on the left side of the engine beneath the airbox. Not to much, otherwise dirt and smale stones will stick on it. Maybe it is dirt or a smale stone that stops the throttle from going back by it self.

On the picture you can see direct under the airbox between intake 2 and 3 is a kind of wheel that moves when you move the throttle and a spring to the left and right.

But it could also be a brocken throttle cable.
Do not put to much WD40.

Wait until somebody else adds a other idea!

Cheers espresso

If you have a BMW cable it should not be lubricated as the liner is made from Teflon. The return spring is located on the throttle lever on the TBs in between #2 and #3.
The problem tho is likely to be your grip is pushed on too far bringing it into contact with the switch block causing the throttle to bind... or possibly your throttle mechanism on the handlebar needs grease. Something that's not too sticky.
If all that fails, your cable maybe shot.

I had a non return problem with my wife's K75RT and it turned out to be the OEM heated grip wire inside the handlebar was bunched up right at the end of the handlebar. It felt good to turn without any conection to the gears but when it was assembled but was just enough to prevent the return.

Ken 52 - don't know whether throttle friction screws are fitted/legal in USA, but this is another obvious reason why the throttle may not snap back to the shut position on release.



Screws into underside of throttle/front brake lever assembly (if not fitted - may have a soft plastic bung in it's place). Legal in UK - I have them fitted to both my bikes as a crude but effective cruise control. Screwing in the knurled screw increases the friction of the throttle mechanism and stops it snapping back to shut. Screwed in until just tight enough to be effective but not so tight that it interferes with comfortable throttle operation.

Just subjected Heidi to her annual MoT (vehicle safety inspection) - not my usual garage for the MoT, as he decided to wrap his hand in after another lean winter.

Having ridden into the test station, I was kind of reliant on the bike passing so I could get home again. The tester did the usual poking and prodding, brakes, lights, everything OK....apart from the throttle not snapping back to closed. Allegedly this is a MoT failure. Disaster! I pointed out the throttle friction screw - the sole purpose of which is to stop the throttle snapping closed on release and asked how it could be legal to use if the snapping closed action was a MoT requirement. Doesn't make sense at all! I know in other countries, the friction screw is not legal for that very reason.

He had a quick look at the throttle mechanism and my heart sank when he started saying that he'd never seen an arrangement like that before. Not being able to free it up, he went on to tell me that I could leave the bike and he would look at it sometime in the next couple of weeks and probably change the throttle cable. I don't think he appreciated the effort needed to change the cable - partial fairing off, tank off....none of it difficult, but if you haven't worked on a K - it could prove an expensive exercise (he would probably take all the fairing off for starters).

I decided that I would come back with car & trailer to collect the bike and do the job myself. However, while I was still there, I thought that I might as well have a look to see if I could free the throttle up. I checked the usual suspects - the grip rubber was not tight against the non-rotating surface, so not the culprit; the bar end weight was not impeding movement at the other end either; the heated grip wires were not preventing free movement (although the heated grips have ceased to work and need attention anyway); I removed the throttle friction screw completely - but the throttle still would not snap back to closed. Running out of ideas I disconnected the twist grip from the throttle cable - and ah ha, a clue...there was still some light resistance to twisting. Bar end weight off, heated grip wiring brutally disconnected and I was able to slide the twist grip off the end of the handle bars. Beneath the grip, the bars were horrible and rusty. The paint from 25 years ago had worn away and been replaced by a rough surface layer of rust. It took a few minutes to scrape off the worst of the rust (note to self - need to put some wet & dry paper/emery paper in my tool kit), lube the surface lightly with WD40, pull a rag through the twist grip  and then reassemble. Instant success - the throttle snapped back crisply, exactly as it is supposed to. 

Tools re-stowed, I got the tester to check the throttle operation and MoT failure was turned into MoT pass...and good for another year of riding. I rode home happy 

Moral of the story - sometimes it is the simplest things that are preventing proper operation. The stiffness of the throttle operation, due to the corrosion of the handle bar beneath the grip, was masked by my use of the throttle friction screw. 

So, if you are experiencing this kind of problem, don't assume it is the cable that is at fault. I narrowly averted a potentially expensive (due to labour hours) repair - a repair that would have been totally unnecessary - and wouldn't have fixed the problem!

Now I'm home, I need to effect the full repair - clean up the bars and re-preserve properly. I was intending to replace the non-functional OEM grips with Oxford heated grips this summer anyway...looks like this is the boot up the back side I needed to just get on with it!