After a longish ride the other day I decided that the K1 needed a Throttle Body balance. To be honest the fuelling was never right. After any sustained runs at speed and coming to a halt in traffic or at junctions etc the revs would drop away and the engine sometimes stall.

Well with the under-tray off and the left side of the fairing removed I cracked on and discovered that a previous owner had used the BBS (Big Brass Screws) to try and balance the TBs! I discovered this when I removed them for cleaning before starting the process, one was almost at the end of its available thread!

The thing with the 16-Valve bikes is that the idle-speed adjuster isn't at all obvious unlike the 8-Valve models. The fuel rail and injectors are in a different place (as the injectors were moved to make room for the extra valves). There's no way to get in there with anything but a slim ¼ inch drive ratchet and an equally slim 7mm socket.



It's pretty hard to spot it behind the Throttle Bodies and if you didn't know it was there you might think that the BBS were the only way to alter the idle speed.

Anyway, with it all adjusted and running sweetly I left it to today to replace the panels and take it for a quick squirt up the main road to check that all was okay.

I discovered this under the bike this morning (not the screwdriver ):



I'd actually cleaned up what was there at first, the above drip took a few minutes to appear after.

As per the title - Oh well, the weather has turned to crap again so I may as well spend my time in the garage. New seals are on the way from Motobins. I was tempted to fit a new K1200LT oil/water pump - police bikes were fitted with them as the 1200LT pump gives better low speed cooling - but the price put me off.

Good old Motobins. I ordered the seal kit on Tuesday, it arrived Wednesday. You can't ask better than that.



It was all back together by Wednesday evening but I left the Three-Bond gloop to cure overnight before starting the engine. This morning I fired it up and it now appears leak free.

The only cock-up was transposing the oil pressure switch and temperature gauge connections. A glowing oil pressure warning light after messing about with the oil pump is not what you want to see. That comes of not having taken a proper look at what wire went where on stripping it (that and not having a wiring diagram for the bike).

easy to get wrong mike ....even with a diagrame ...

nice work mate !

MikeP wrote:Well with the under-tray off and the left side of the fairing removed I cracked on and discovered that a previous owner had used the BBS (Big Brass Screws) to try and balance the TBs! I discovered this when I removed them for cleaning before starting the process, one was almost at the end of its available thread!

Um Mike, your explanation regarding the PO's adjustment (and your subsequent adjustment of the throttle shaft position screw) goes contrary to advise that I've read on the Motbrick and BMWMOA forums. I'll refer to this post, for example. This post specifically advises against touching that screw; and that the BBS should be used to achieve TB balance and idle speed. I've seen similar advise on other forums as well supporting this view. It seems to me that BMW doesn't want the mechanic to fiddle with the throttle shaft position screw otherwise why would they have buried it deep inside the TB assembly inaccessible by any tool other than a low-profile socket. With differing methods described, it's sometimes confusing as to who is correct and who is incorrect.

I go along with the reply at post number 9.

The BBS adjusts the balance but not the idle speed.

makes sence mike ..ill go along with tbps screws adjusted close together near the suggested, and adjust idle as heat soak is reached ...then set the tps as it should be .this way it ensures that relative vacuums are reached at the inlet manifold and the maping of the fuel delivery is correct from idle up ..

MikeP wrote: The only cock-up was transposing the oil pressure switch and temperature gauge connections. That comes of not having taken a proper look at what wire went where on stripping it.

I've now gone over to taking pictures of these assemblies before taking them apart.

charlie99 wrote:makes sence mike ..ill go along with tbps screws adjusted close together near the suggested, and adjust idle as heat soak is reached ...then set the tps as it should be .this way it ensures that relative vacuums are reached at the inlet manifold and the maping of the fuel delivery is correct from idle up ..

That's the way I see it.

I remove and clean the BBS (a small dab of rubber "food" or red grease on the O-rings). Replace them until they just bottom-out, then turn them out one full turn.

I attach my mercury manometer (the "control TB is cylinder #1 on 16-Valve bikes as opposed to #4 or #3 on the 8-Valve K100 and the K75).

As I have a throttle lock, I start the bike and set the throttle to just about the first position of the cold-start lever.

Once it's up to normal operating temperature, I use the BBS to balance the throttle bodies at around 2,000 rpm and at the recommended idle speed.

That done, the throttle is closed and if the idle has been affected by the balance, adjust it with the idle screw.

This means that the balance is not altered by re-adjusting the BBS. The idle screw just cracks open or closes all the now balanced TBs together.

Check the TPS by the "click" method.

Then check and adjust the gaps for the two fast-idle positions via the cable adjuster being sure to leave the recommended slack.


Perhaps someone here knows: On the Oilhead Boxers, the TPS can be set by measuring the voltage across the terminals one and four of the connector. The same TPS is used on all the bikes the that use the Motronic "brain".

The ideal voltage is 0.36 and between 0.32 and 0.4 volts is acceptable.

Does anyone know what the voltage should be for K-Series? Would it be any different just because there are more than two cylinders?

Here's a "how to" for the Boxers (I always used the second method):

http://advwisdom.hogranch.com/Wisdom/tps3.1.pdf

0.375V with the electrics enabled but the engine not on, as per this write-up on Motobrick: Adjusting the TPS (Throttle Position Sensor) on a 4V K bike

Brilliant. Thanks for that, I'll check with my wires and meter later (I think that it's a better method than listening for an almost inaudible click).

Can I add, remove the TPS altogether then set up as described, lastly fit and set TPS.

I think the TPS needs to be present & correctly adjusted while balancing & setting the idle stops.
Reason. Setting the BBS screws is done at about 1500 RPM hence the switch is open.
Setting the base hot idle speed is done accomplished at its final setting with the TPS closed.

OBTW......some fellas here remove or disconnect the TPS entirely. I don't recommend doing that.
I may not understand it's function completely, but in my experience, it's reason is to cut off fueling completely when throttle closed with the engine turning above 1500 (deceleration) to aid in engine braking and prevent exhaust backfire.
It is a duel function switch that also closes a second set of contacts at WOT signaling maximum enrichment to the FI controller.

I don't quite see the benefit of removing the TPS. I'm a bit thick when it comes to this stuff so I'm open to persuasion.

Anyway (sorry about the flare but the mercury is just about visible):



Then thanks to robmack:



(it was quite a way off just using the "click" method)

It sounds a lot better, a ride will tell.

MikeP wrote:After a longish ride the other day I decided that the K1 needed a Throttle Body balance. To be honest the fuelling was never right. After any sustained runs at speed and coming to a halt in traffic or at junctions etc the revs would drop away and the engine sometimes stall.

Well with the under-tray off and the left side of the fairing removed I cracked on and discovered that a previous owner had used the BBS (Big Brass Screws) to try and balance the TBs! I discovered this when I removed them for cleaning before starting the process, one was almost at the end of its available thread!  

The thing with the 16-Valve bikes is that the idle-speed adjuster isn't at all obvious unlike the 8-Valve models. The fuel rail and injectors are in a different place (as the injectors were moved to make room for the extra valves). There's no way to get in there with anything but a slim ¼ inch drive ratchet and an equally slim 7mm socket.



It's pretty hard to spot it behind the Throttle Bodies and if you didn't know it was there you might think that the BBS were the only way to alter the idle speed.

Anyway, with it all adjusted and running sweetly I left it to today to replace the panels and take it for a quick squirt up the main road to check that all was okay.

I discovered this under the bike this morning (not the screwdriver   ):



I'd actually cleaned up what was there at first, the above drip took a few minutes to appear after.

As per the title - Oh well, the weather has turned to crap again so I may as well spend my time in the garage. New seals are on the way from Motobins. I was tempted to fit a new K1200LT oil/water pump - police bikes were fitted with them as the 1200LT pump gives better low speed cooling - but the price put me off.  

4 years old post I know - but the photo of the "idle speed adjuster screw" was just the motivation I needed - thanks!  I've been bothered by my 1300 rpm idle since buying my K100RS a month ago.  I read this thread a couple of weeks ago and finally got around to doing something about my high idle.  Most of my riding is in a rural back country setting (motorcycle heaven around here - especially this summer with 10 weeks w/o rain!) so I don't sit at idle much, but I had to run some errands in town yesterday and my idle drove my temperature right through the tank and into my thighs!

You mentioned about how difficult it is to get at the adjustment screw, having to use a small ratchet & socket.  However, I noticed that with my throttle lock on to hold my throttle fully open (and a piece of plastic from a cottage cheese container used as a wedge between the switch body and grip would suffice too), the idle adjust screw rotates to the front, making for very easy access.  Then I used a slot screw driver to visually ascertain the amount of degrees I was turning the screw (yes, you can do this with a ratchet also, but the socket blocks your line-of-sight of the adjustment screw).  Turned it CCW 3/4's of a turn (that's 270° Laitch) which brought my idle to dead on 950 rpm +/- 50.  Sweet!

Thanks again for the pic, Ace