trying to lower idle (currently idles at approx 1250 on the tach when fully warm) on my '91 k100rs w/ motronic with what appears to be the idle screw (attached to throttle cable mechanism on throttle body) but turning it makes no difference. i suspect it's NOT adjustable. i adjusted the throttle position sensor (tps) using the 3 pin connector on my bike and it's spot on. i checked for air leaks and all is fine. only other way i know to adjust idle is timing by i don't want to mes w/ it yet.

Have you tried slackening the throttle cable at the grip it may be hanging there. The adjuster id hidden under a small tapered rubber sleeve which is right at the end of the cable where it enters the grip.

Rick G wrote:Have you tried slackening the throttle cable at the grip it may be hanging there. The adjuster id hidden under a small tapered rubber sleeve which is right at the end of the cable where it enters the grip.

i have lots of experience troubleshooting cars & bikes so i've done all the basic stuff including what you suggested. i just want to conform if idle is adjustable on motronic?

Welcome to the forum. When you get a chance go to the 'member's introduction' page and tell us about yourself and your bike(s) - we like pictures too! I hope you resolve the idle issue satisfactorily. There are many here who are ready, willing and quite able to offer sound technical advice.
Cheers.

Rick G wrote:

browe58 wrote:

Rick G wrote:Have you tried slackening the throttle cable at the grip it may be hanging there. The adjuster id hidden under a small tapered rubber sleeve which is right at the end of the cable where it enters the grip.

i have lots of experience troubleshooting cars & bikes so i've done all the basic stuff including what you suggested. i just want to conform if idle is adjustable on motronic?

According to the K1100 manual the idle speed is adjusted by the air bypass screws and you must not touch the idle adjustment screw as it is sealed with lacquer. Thats good ol BMW for ya
Adjusting idle speed
L Note:
The basic setting (ignition, valve clearance) must be
correct.
• Remove knee pad.
• Remove left side fairing.
• Remove protective caps (1) at the vacuum connections.
• Connect connection hoses of the Synchrotester,
BMW No. 13 0 800, one after the other (note
hose markings 1-4 on tester housing).
• Connect tester to vehicle with the corresponding
adapter lead.
• Start engine and run at a standstill for app. 10
minutes if not already warm.
e Caution:
Do not run for more than 20 minutes at a standstill.
• Run the engine at idle speed.
• Select “bar diagram” and maximum resolution.
L Note:
If the differences between the individual columns
are too great (more than 2...5 mm
(0.07874...0.19685 in)), switch over to curve display
and compare the individual cylinders with each other;
perform fault diagnosis procedure if necessary.
• Repair any faults found.
e Caution:
Throttle adjusting screw (2) is secured with lacquer
and must not be turned.
• Adjust synchronisation and idle speed by turning
the air control screws until the bars/curves are at
the same height; adjust engine idle speed.
Idle speed ......................................... 950 ± 50 rpm

sounds more like the procedure for synching the carbs (really meant to say balancing tb's!!!) . which manual are you quoting from? is that the procedure for motronic??? i have clymers and the procedure is different but when i try it, it makes no difference. i think most of the manuals suck cuz they try to address so many different bikes and usually get it wrong. so i still suspect it's NOT adjustable on motronic.

BMW Factory manual for 1993 K1100 which is the same as a K100RS 16v.

when you sinc the throttle bodies, start with the brass screws about one turn out, that will keep the rpms down, because you may be at the end of the adjustment on the cable.

Rick G wrote:BMW Factory manual for 1993 K1100 which is the same as a K100RS 16v.

damn, seems like a lot just to adjust idle. guess i'll leave it alone for now and chase down my vibration issue. thanks

Rick G wrote:BMW Factory manual for 1993 K1100 which is the same as a K100RS 16v.

hi, i read one of your posts for tb balancing and you referenced the bmw service manual. one of the procedures is to listen to the tps click. on my bike i have a different tps. mine is does NOT click. it's a potentiometer. so i wonder if the tb balancing procedure would be the same for my bike?? please clarify. thanks.

Of course, it's important to keep in mind that adjusting the TBs using the air screws (and therefore the idle) is only syncing them at idle and very low rpm. If you are chasing the source of typical K vibrations look for those vibes due to air leaks in the post TB intake (vacuum leaks), loose chassis to driveline mounts, even dry splines.

Guest in the House wrote:Of course, it's important to keep in mind that adjusting the TBs using the air screws (and therefore the idle) is only syncing them at idle and very low rpm. If you are chasing the source of typical K vibrations look for those vibes due to air leaks in the post TB intake (vacuum leaks), loose chassis to driveline mounts, even dry splines.

would that be clutch or driveshaft spline or BOTH? so these bikes use rubber mounts? how many are there? thanks.

browe58 wrote:
would that be clutch or driveshaft spline or BOTH? so these bikes use rubber mounts? how many are there? thanks.

Your bike has solid engine/driveline to chassis mounts, but check to see if there's any flexing and movement when you loosen the frame to gearbox bolts. On my '87 K100RS I had to shim the left hand side with flat washers as the frame needed to be flexed inward to comfortably rest against the aluminium of the 'box. Check the forward engine mounts for this 'flex' as well. There are no rubber mounts.

The splines are: at Paralever, output shaft and the gearbox input shaft/clutch. These being in need of the usual lube maintenance do not 'cause' major vibes, but lubing them can alleviate some tingling and certainly improves the clutch and shift action.

I note you have read as much as you can about the inherent vibes and their causes on these machines. Mine, even after careful ignition timing, valve shim clearance check, spline lube, intake sleeve rubber replacement, TB idle sync & vacuum cap replacement, wheel/tyre balance, handlebar rubber mount check, wheel and frame alignment, footpeg mount check, and etc., still has a vibe that won't allow me to comfortably sit at about 110 km/h (at 4500 rpm), our national speed limit. I can go 100 km/h or 120 km/h and everywhere else just fine all day long. Others have a similar trait in their machines, but it can differ at certain speeds/rpm. I have gotten used to it, thought it can be frustrating at times. They never were the smoothest of bikes from go. The K1100 (basically the same as your 16V K100) was a bit better, but the K1200 series was far better.

Additional note: I have a set of high quality analogue vaccum gauges which I use to sync the TBs at idle. After getting them as close to even as possible and then revving the motor to the rpm at which I ride most, the TBS are spot on (as measured only through the vacuum ports). Be very careful if you are going to attempt to sync them at rpm as they are incredibly fussy about having their between TB balance set screws mucked with.

Guest in the House wrote:

browe58 wrote:
would that be clutch or driveshaft spline or BOTH? so these bikes use rubber mounts? how many are there? thanks.

Your bike has solid engine/driveline to chassis mounts, but check to see if there's any flexing and movement when you loosen the frame to gearbox bolts. On my '87 K100RS I had to shim the left hand side with flat washers as the frame needed to be flexed inward to comfortably rest against the aluminium of the 'box. Check the forward engine mounts for this 'flex' as well. There are no rubber mounts.

The splines are: at Paralever, output shaft and the gearbox input shaft/clutch. These being in need of the usual lube maintenance do not 'cause' major vibes, but lubing them can alleviate some tingling and certainly improves the clutch and shift action.

I note you have read as much as you can about the inherent vibes and their causes on these machines. Mine, even after careful ignition timing, valve shim clearance check, spline lube, intake sleeve rubber replacement, TB idle sync & vacuum cap replacement, wheel/tyre balance, handlebar rubber mount check, wheel and frame alignment, footpeg mount check, and etc., still has a vibe that won't allow me to comfortably sit at about 110 km/h (at 4500 rpm), our national speed limit. I can go 100 km/h or 120 km/h and everywhere else just fine all day long. Others have a similar trait in their machines, but it can differ at certain speeds/rpm. I have gotten used to it, thought it can be frustrating at times. They never were the smoothest of bikes from go. The K1100 (basically the same as your 16V K100) was a bit better, but the K1200 series was far better.

oh my god, you just crushed all my hopes of making this bike a keeper. i have 3 bikes and have owned the 100rs for 4 days so i'm not attached to it. how can bmw claim a max speed of 130 mph on this bike if it wasn't smooth from the get go??? bike is silky smooth from 40-55 mph. once i hit 60 mph (4k rpm's) it goes down hill. granted, most of my riding is on winding back roads where max speed is under 60 mph and bike really excels. but there are always stretches where you want to open it up to 70 and that's where it gets too buzzy for me. so i guess i have to live w/ it or get another bike if i 'm looking for something silky smooth up to 100 mph. 3 quick questions......

1. when i let go of the handlebar the bike pulls to the right? what are the common causes?

2. what motor oil do you recommend to minimize vibration? i'm running rotella 15w40 dino. would synthetic help? i have synthetic 75w90 in tranny and final drive.

3. have you played around w/ different spark plugs?

Pulls to right...possible camber of roads in New England, too soft tyre inflation (run 38-42 psi front/40-44 psi rear) or crap tyres, stuffed/notchy steering head bearings, etc.

Rotella diesel oil is excellent and recommended here for keeping the engine/starter sprag clutch clean but makes no difference to vibes.

I use NGK DP8EAV-9 (projected tip, palladium, cooler heat range - DP8EA ok too), as opposed to D7EA but that's my personal choice in a much hotter climate than yours and an 8V engine. Note that they are non-resistor, no capital R in the number (Thanks, Charlie!). The ignition lead caps do the 'resisting'.

Don't give up. They are an awesome machine with some TLC and attention to detail. It was always going to be a compromise motor as compared to UJMs and other engine configurations due to its lop-sided nature. But they have their charm and their quirks too. There are very many of us with very very many millions of miles/kilometres under our wheels successfully with these bikes. If you just can't stand it, and you've given it your all, read and studied everything you can, adjusted and played and toyed and fettled to your dying day, then back away and let someone else have a go.

Mine vibrates at 100kph ( 4,000rpm) and then smoothes out at 110kph.....I guess they're all different.

Yep, they're all different, but I find they smooth out the faster you go. At 120 km/h I can see the cop's blueberries and cherries clearly flashing behind me. At 140 km/h I can see them still, but at 160 they're diminishing, flashing coloured specks in my mirrors all the way to 245 km/h!

Guest in the House wrote:Pulls to right...possible camber of roads in New England, too soft tyre inflation (run 38-42 psi front/40-44 psi rear) or crap tyres, stuffed/notchy steering head bearings, etc.

new dunlop tires and steering head bearings. my other bikes track straight when i let go so there's something off w/ this one. i i adjusted tires pressure and emptied hard cases and it still pulls to the right. tires out of balance? in there an alignment procedure for these bikes? thanks so much.

hmm ...could have the spacers installed incorrectly - on the front wheel axle ...or some sag in the springing ?

With regard to pulling to the right make sure the spacer is between the rear wheel and rear drive, its about 2mmm, as that can mess with the handling especially if you are using bias ply tires.

browe58 wrote:
how can bmw claim a max speed of 130 mph on this bike if it wasn't smooth from the get go???

Sorry browe58, They claim it because it does do 130 mph, and that's 23 years later

Rick G wrote:With regard to pulling to the right make sure the spacer is between the rear wheel and rear drive, its about 2mmm, as that can mess with the handling especially if you are using bias ply tires.

rick, you're a freakin' genius and saved my life!!! the damn spacer in the rear is missing. now i have to track one down. plenty of dealers in my area but NONE are open on mondays. i suspect once it's on, the bike will be transformed and i'll end up keeping it. i'll keep you posted. peace. btw, looks like it's shared by several bikes and offered in 2mm or 3mm.

Guest in the House wrote:I use NGK DP8EAV-9 (projected tip, palladium, cooler heat range - DP8EA ok too), as opposed to D7EA but that's my personal choice in a much hotter climate than yours and an 8V engine. Note that they are non-resistor, no capital R in the number (Thanks, Charlie!). The ignition lead caps do the 'resisting'.

i checked ngk's website and they call for a dr7ea for '90-92 k100rs

That's right for 16V engines, whereas mine is an 8V. I prefer the projected tip and mildly colder heat range, since there's no clearance issue there's no worries, and the flame front is that smidge further into the combustion chamber.

Rick G wrote:With regard to pulling to the right make sure the spacer is between the rear wheel and rear drive, its about 2mmm, as that can mess with the handling especially if you are using bias ply tires.

hi rick, i've done some research on the shim and it appears that some riders and dealers have intentionally removed the shim to eliminate pulling to the right. now i;m not sureif it will make a difference on my bike. nonetheless, to be on the safe side, i'm going to put it back like it was designed by the bmw engineers. peace.

captaink wrote:

browe58 wrote:
how can bmw claim a max speed of 130 mph on this bike if it wasn't smooth from the get go???

Sorry browe58, They claim it because it does do 130 mph, and that's 23 years later

You also have the Boost Button for that little extra :silent: