K1100lt throttle body issue

[dc007]

Hello all, Ive gotten my k1100's engine all put back together and it no longer leaks oil so that issue is buttoned up and fixed. However after trying to start the bike I cant get it to idle quite right. The screws between the throttle bodies were far out of adjustment when they never should have been touched, so I researched a way to get them all balanced while on the bike, which has worked and all 4 are pulling 10-12 inches of vacuum at idle. Problem is, it idles at about 2000 rpm and nothing will seem to lower it. There is free play in both throttle and choke cables, the idle adjustment screw is not seated and the tps sensor does not seem to be causing the issue. I check the airbox boots and they are on tight, same with the intake boots. Im completely out of ideas so all help is appreciated, thanks! I can try and provide pictures/video if that will help too.

[Laitch]

The screws between the throttle bodies were far out of adjustment when they never should have been touched, so I researched a way to get them all balanced while on the bike, which has worked and all 4 are pulling 10-12 inches of vacuum at idle.

Which screws—the screws with blue paint or the brass screws?

[dc007]

The ones that were misadjusted were the painted screws, albeit only slightly but I could measure a good bit of difference between throttle plate openings with a caliper. The brass screws were seated lightly as per the inter-body balancing procedure I was following. A while after my post I took the whole throttle body assembly back out and noticed the intake o rings were perished on the 2 cylinders with low vacuum. Im going to replace all 4 tomorrow and try again but that should hopefully solve most of my issues here.

[dc007]

Quick update, I replaced those O rings and got it all put back together and balanced the inter body screws to be equal in vacuum  . The bike ran very smoothly and I was able to take it out and ride around town just to make sure everything was right. Only problem I noticed is that the bike dies on deceleration when the clutch is pulled and throttle quickly released to idle, but this only happens when its on the colder half of the temp gauge. My idle level is not too low as the tach reads a steady 1000-1050 rpm. My klr had this exact issue of dying when cold and my temporary fix was to just bump up the idle, but I want to get this bike running right so id prefer to not do that.

[Laitch]

Please link to, or share, the "inter-body balancing policy" you were following. It might benefit somebody else.

[dc007]

Here ya go

https://www.k100-forum.com/t1526-how-to-balance-the-throttle-bodies-solved     

[Laitch]

That's a classic thread. Keep in mind that its main subject is timing of the two-valve K100 and K75 models. Your K1100 is slightly different. Nevertheless, did you check for un-metered air leaks as suggested by Lentini and Eilenberger? Did you verify that the air filter is unclogged and the fuel filter freely flowing? The engine should idle well after a couple of minutes warmup.

As you are aware, your engine should not stall at idle after deceleration when air balance is at 950–1050 rpms. Did you check the throttle position sensor setting? Its procedure is found on page 13.8 of the K1100 manual downloadable at Motobrick.

[dc007]

I fixed all my air leaks and I was able to achieve a good idle after warmup. I’m In the inevitable situation of taking one step forward and 2 steps back as the fuel pump screen is clogged with gunk from the tank, but that can be cleaned easy. The throttle body isn’t quite right yet but I know whats out of adjustment and how to get it right again, so I’m going to do that later today. Hopefully I should get it running proper later. If I succeed in that I’m thinking of typing up a detailed step by step of what I did in adjusting the throttle body and how it differed from the thread I followed because I don’t see that information anywhere else, so it might be useful for someone else in the same boat.

[Laitch]

I’m in the inevitable situation of taking one step forward and 2 steps back . . .

Don't be so hard on yourself. This situation could seem unenviable but certainly is not inevitable, unless you're involved an ancestral curse. Even with that, there are remedies to be found in voodoo and Santería.
 

[dc007]

I'm scratching my head quite a bit here trying to figure this out, as I was under the impression that I completely understood my issue and how to fix it, but it seems it has only gotten worse.

The following might have loads of useless information but I want to give as much detail as possible in case any of it is crucial:

When I had the bike up and running the other day, it sat nicely at 1000 rpm. All of the throttle butterflies were balanced, however I made the mistake of using the main idle stop screw (the one at the back of the throttle bodies) to set the idle, not the brass screws, I left the brass screws fully seated. I took the bike out for a ride and I noticed the bike would stall when rolling off the throttle quickly. Then about 5 miles later the fuel pump became very loud and the bike started to stutter, which I determined to be because of a clogged pump screen which is now cleaned and fixed and my pump sounds normal. I came to the conclusion that this was my issue: I used the throttle stop screw to set the idle, propping the butterflies too far open which meant that the bike could run with the brass screws seated. My solution as I thought was to set the throttle stop screw to a very low baseline (the lowest rpm the bike can continue running at) as it seems to be intended for, and then use the brass screws to return the bike to a balanced idle of 950 ish rpm. about 30 minutes ago I went through this procedure and got the throttle bodies to have a balanced vacuum of about 10 inHG, however the bike now does not idle steadily. It wanders all over the place from 900-1100 rpm and sounds like its trying to die, additionally when I give it throttle up to about 2500 it does not smooth out much and occasionally backfires. I decided to check again for vacuum leaks with an acetylene torch and found nothing. Lastly, I read in a forum that k bikes should not be able to run with the oil cap taken off as it will cause a massive vacuum leak, however mine continues to idle erratically with no change when I unscrew the cap completely.

Sorry for the word salad here, I figure the devil is most likely in the details with this one so I should probably give as much detail as possible.

[Scott_]

Mine will also run with the oil fill cap off, slightly erratic, but will still run.

[dc007]

hmmm, I think tomorrow ill go through the whole intake system with a fine toothed comb, so to speak. I found another 2 threads that detailed which vac lines in and around the airbox could be plugged off so I think ill try my hand eliminating all the unnecessary emissions vac lines in case they're causing leaks. Not sure if it'll be fixed but it'll be different!

[Laitch]

I made the mistake of using the main idle stop screw (the one at the back of the throttle bodies) to set the idle

Could you post a photo showing the location of the "main idle stop screw?' Is it one of the parts enumerated in the diagram below?

[dc007]

Im not by the bike at the moment but I will be later today and I can take clearer pictures, but for now this is the clearest picture I can find online.



Unfortunately it seems there is no diagram in the manual to show this screw. The screw is located on the back underside of the throttle body between bodies 2 and 3.

I believe it is functionally the same as the screw that faces down and pushes against a plate on the front left of a k75’s throttle body, which you are probably more familiar with.

[Laitch]

Im not by the bike at the moment but I will be later today and I can take clearer pictures, but for now this is the clearest picture I can find online.

I believe it is functionally the same as the screw that faces down and pushes against a plate on the front left of a k75’s throttle body, which you are probably more familiar with.

Don't bother looking for a photo; I found a detailed high res version.

I really don't know whether this thread is a spoof, or that you really believe you can navigate your way without consulting the clear instructions in BMW's manual. The results are clearly showing that the current strategy is failing.

My parting observations from this thread are:

• If that painted screw on the back side of the throttle body is part of a TB setting procedure meant for an ordinary dooryard mechanic, its purpose would likely have been explained. It's inconvenient location should have been a hint to either leave it alone, or query its purpose from those with experience, rather than presume its purpose by conflating it with a different model's similarly looking part.
• There are a few checks and possible corrections that must be made to other parts of the system before the actual balancing of the TBs is undertaken and a few essential steps afterward. The manual identifies those steps. Your approach seems to be scattered.
• Returning to Square 1 might be a good option. Accept that the throttle plates were probably ok and return the painted screws so each screw's paint marks on the plate or nut and the thread are back in alignment. If the screw on the backside had marks, do the same. Other choices are to work with what you've done, consult with those who inspired you to take that throttle plate adjustment step, or go to the manual and follow the instructions.

Like I've indicated when it comes to my Brick, I always turn to the manufacturer's instructions first even if BMW's translations to English sometimes need deciphering. Haynes and Chilton manuals are secondary references mostly used for comparing photos and diagrams. Also, I've learned valuable lessons from fellow riders here and elsewhere by applying the doctrine, Trust but verify. My most valuable lessons have been from the mistakes a legion of others have made so I don't need to make them myself and deprive myself of valuable riding time. I'm grateful that they have been published. That's the beauty of the Internet.
  
Good luck with your project!

[dc007]

Thank you Laitch and Scott for your help with this issue and my previous one involving the oil leak.

No this is not a spoof, I do not see what “clear instructions” you are referring to. Unless I am brushing over something obvious, neither the official bmw service manual (https://www.bskspeedworks.co.uk/downloads/BMW__K1100LT_K1100RS_Repair_Manual.pdf )
nor the clymer manual describe how to adjust the interlinkage screws or the stop screw to get me back to square one. Bmw says in their manual “dont touch the screws” and the manual telling me the problem shouldn’t exist does not help me solve the problem. Clymer says if the interlinkage screws are touched to replace the whole unit, and I would believe that to be necessary if there were not several threads describing how that is not necessary, and how its an easy fix, an easy fix that I have performed. I’ve combed through appropriate sections of the bmw and clymer manuals a few times over again today to see about the throttle stop screw to no avail, so I struggle to see exactly what options I have left besides trying to fix the problem on my own through trial and error or asking people who are more knowledgeable than me (as I have done here).

Thank you for your help and the good luck, I’ll see what I can get figured out.