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F***ed up throttle bodies


Brycelyoung

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So, I finished reassembling my bike ('98 R1100R) after a clutch replacement. Went to start it up today and it's idling way too high (somewhere around 3000 rpms). In addition, the header pipe coming out of my right cylinder began to glow red hot after maybe only a minute of sitting there). I turned the BBS all the way in and it dropped the RPMs maybe a couple hundred at best. I'm guessing the gross idle stop screws got f***ed up somewhere along the way. What do y'all recommend? I'm not one to get easily frustrated with mechanical problems, but this really makes me feel uneasy. I'm ok bringing it to a mechanic, but I would not feel good riding it to a dealer with the RPMs idling that high. Is there any possibility of backing off the stop screws to a certain point so I can ride it to a mechanic? Any advice (or follow-up questions) would be greatly appreciated!!!

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Evening Brycelyoung

 

 

Don't get too excited yet.

 

First, check to MAKE DARN SURE that the R/H throttle cable at the R/H Throttle Body is IN the adjuster ferrel & not sitting on top of it.

(very common problem at reassembly & easy to remedy)

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I think I did check that (and remember reading it in Clymer), but will double check when I can (I'm at work now).

 

Evening Brycelyoung

 

You need to look closely as it is easy to miss the cable being wrong. Or pull the cable housing out a little then see if it snaps back into the furrel.

 

Or a good/better check is to reach in with a hand on both side TB cams then have someone else carefully open the twist grip--- if correct both sides should lift off the base idle screws at the very same time & also hit the wide open stops at the very same time.

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First, take a deep breath. Something is wrong, but it is something simple. First question, are the butterflies closing all the way to the stops? If you look from under the bike you can see them, or you can listen for the "snap" as you roll the throttle off. Speaking of the throttle, how does it feel? Is there extra slack in the throttle cable?

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Don't forget to check BOTH ends (meaning at the hand grip as well). As well as both ends of the cable housing, make sure that both ends of the cable itself are seated properly in their respective spots. Easy for cable ends to unseat and have the same effect.

 

Assuming that is double checked, would it work to simply disconnect the throttle cables and have it idle properly? Never tried it myself on these oilheads, but I'd think if you remove the cable from the equation, it should idle properly. Maybe someone can chime in on that point?

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Alright, stop and think about this. You've got the mechanical skills to do a clutch and you're freaking out about this. Relax, take a deep breath and carefully backtrack from the tb's back and the problem will become obvious.

 

Secondly, I really wish folks would fill out their profile. There's almost always somebody close by who would be more than happy to stop by and put a second set of eyes on it and who knows, you might find a new riding buddy

 

Tom

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So, I finished reassembling my bike ('98 R1100R) after a clutch replacement. Went to start it up today and it's idling way too high (somewhere around 3000 rpms). In addition, the header pipe coming out of my right cylinder began to glow red hot after maybe only a minute of sitting there). I turned the BBS all the way in and it dropped the RPMs maybe a couple hundred at best. I'm guessing the gross idle stop screws got f***ed up somewhere along the way. What do y'all recommend? I'm not one to get easily frustrated with mechanical problems, but this really makes me feel uneasy. I'm ok bringing it to a mechanic, but I would not feel good riding it to a dealer with the RPMs idling that high. Is there any possibility of backing off the stop screws to a certain point so I can ride it to a mechanic? Any advice (or follow-up questions) would be greatly appreciated!!!

 

 

Hi Brycelyoung, Since you've checked the throttle cables. I've got some questions about your report.

 

To idle that high, the engine has to be getting more air than it needs. You say that the throttle stops got messed up "somewhere along the way". Did you have the TBs removed from the bike or did you adjust the throttle stop screws?

 

You mentioned that one pipe is glowing red at idle. That sounds like maybe one of the cylinders is running differently than the other from more air, like a partly opened throttle plate. Have you confirmed that the throttles are making a hard touchdown on the throttle stop screws?

 

Did you remove the throttle bodies while doing the clutch?

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Alright, so I checked, and the cable is seated properly on both sides. Any thoughts?

 

 

Morning Brycelyoung

 

It still sounds like you have a cable pulled out of something in the throttle system.

 

Make sure that the choke cable is not pulled out of the Bowden box or pulled out of the adjuster (at left handlebar under rubber boot)

 

Then do the same for the throttle cable at both ends & under the rubber boot up by the R/H handlebar.

 

Then check the short cables for being properly seated in the Bowden box.

 

Also verify that nothing (like a wire of hose) is caught between a TB cam & idle stop (also verify that nothing is interfering with proper TB cam return)

 

Verify that BOTH side throttle cams lift off their base idle stops & hit the wide open stops at the very same time per my post above.

 

With your high RPM's at ide it sure sounds like you have a slightly open throttle valve (or both throttle valves) or an air leak into the intake area (between a throttle valve & cylinder head.

 

Bottom line here--- You need to verify that BOTH side TB throttle cams are SOLIDLY resting on the base idle screws at idle & that you have no air leaks in the intake system (like an intake boot pulled slightly loose)

 

bowden%20box_zpskiikrqzx.jpg

 

 

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More--

 

I forgot to mention in the post above to also check the vacuum nipples on the bottom of the Throttle Bodies to make sure that the hoses are still firmly attached (or vacuum plugs if your evap system has been removed)

 

If the hoses are still attached to the bottom of both TB's then follow the hoses to make sure that they are connected to the solenoid (on L/H side of bike) & at the vacuum TEE where the hoses come together.

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Alright, stop and think about this. You've got the mechanical skills to do a clutch and you're freaking out about this. Relax, take a deep breath and carefully backtrack from the tb's back and the problem will become obvious.

 

Right, the reason I'm "freaking out" (not a wholly inaccurate description, probably) is because from what I'm looking at, my diagnosis most likely points to a problem which is very difficult to fix, namely, misadjusted stop pins on the throttle bodies. If I remember correctly, these are not really ever supposed to be adjusted. The blue loctite has been broken, which means that it's at least been moved a little (right?), and that would account for the right cylinder heating up far more than the left. If it were a problem at the handle end, both sides would be heating up equally (or, at least close to equal), right?

To be clear, I don't mind taking my time or doing work that might be difficult. What I would not be excited for is trying to readjust a pin that few people even know how to adjust since it's not supposed to be moved in the first place. Perhaps I just fear the unknown! Wow, even motorcycle maintenance can be a soul-searching experience, apparently. :grin:

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Yes, throttle bodies were removed completely (in hindsight, I think I could have just done a partial removal). I definitely didn't do any intentional adjustment of the the screws, but from what I could see, it looks like the blue loctite is not intact at least on the right side. This is what is leading me to believe that perhaps it got moved or something in the process. The throttles are touching the screws on both sides.

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Adjusting the TB's from messed up stop screws is not frightening and can be done. I had to fix mine after some work I messed up as well as what the previous owner had messed up. If you search the forums you should be able to find a thread Roger started on the zero=zero method and how that should actually be done. It takes time, but if you are certain one of them is not right then it is worth it. One sure way to tell if one cylinder is off from the other is to put a manometer on them.

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The other thing that could cause your problem is an air leak on one of the TB to cylinder heads.

 

I don't think it is a throttle stop screw problem. It takes only a little extra air to get to 3000 rpm with no load.

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The hot side is running too lean. You probably tore the o-ring on the TB on the side that is running hot when you put the TB back into the rubber/plastic manifold that attaches to the cylinder, and it is drawing in unmetered air.

Spray some WD 40 at the TB/manifold juncture to see if it changes the idle.

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The hot side is running too lean. You probably tore the o-ring on the TB on the side that is running hot when you put the TB back into the rubber/plastic manifold that attaches to the cylinder, and it is drawing in unmetered air.

Spray some WD 40 at the TB/manifold juncture to see if it changes the idle.

 

Good call, except I'd rather use propane gas for detecting air leaks. No messy residue or soaked rubber.

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Morning__

 

You guys need to qualify the "hot side running lean" condition as that isn't always the case.

 

Just disconnect a fuel injector on one side then run then engine. That VERY lean side pipe will be cold to the touch while the other side is running glowing red hot.

 

While it is true that running down the road, under road-load, that a slightly lean cylinder can run hotter. As a rule at high-no-load idle the side doing the most work will run the hottest at the exhaust pipe due to--well doing the most work & producing the most heat.

 

If one cylinder is taking in a normal amount of (or even too much) air at idle but not enough fuel to properly ignite it then that side will run colder not hotter due to less fuel BTU's available & more colder air intake to cool it.

 

About the only time you will see one side cyl exhaust pipe run hotter at idle/high idle is if the mixture is j-u-s-t lean enough (or j-u-s-t rich enough) to not light off properly on time so it lights off late & is burning strong as the exhaust valve opens therefore allowing full mixture burn as it enters the exhaust pipe.

 

 

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Well said DR. As a further clarification, in a properly igniting mixture on our bikes, peak EGT occurs at lambda = 1 (14.7:1). Any richer or any leaner and EGT is LOWER.

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So here's the update. I adjusted the right throttle body to more or less visually resemble the left side. I know that this is probably very imprecise and not a good technical solution. However, I was still able to get the bike to run around 12-1300 rpms and it seems pretty steady. I was planning on bringing the bike in to get a real sync anyway, so this should do for now, correct? Right now, the throttles hit the rest pins at the same time, but the right throttle does not hit the wide open throttle tab (there's gotta be a technical name for that, eh?). This shouldn't be too big of a problem just riding to a technician, right?

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If the right is not hitting the wide open tab at the same time as the left then the cables are not in sync. This would also mean your stop is incorrect on one or both throttle bodies. Unless you are absolutely certain the left side has not been touched I would go through setting the zero on that one. Best way to do this is as follows (check the TPS voltage as it is currently before starting this): 1) loosen the cable, 2) back off the stop screw until you have a gap, 3) attach a meter to pins 1 & 4 on the TPS and loosen the screws, 4) with the butterfly fully closed adjust the TPS position for close to 0mv, 5) adjust the throttle stop until the TPS reads ~130mv (I'm going from memory so look up the other threads on this please). This will set your butterfly opening close to the proper resting opening position. Now, lock the stop screw in this position. Next, position the TPS to read 370mv.

 

Now, for the right side, you'll need to adjust the cable to get both hitting the wide open tab at the same time. After doing this I would back off the stop screw just to the point where you have a slight gap. At this point, IIRC, I started the bike and warmed it up some then adjusted the stop screw to get fairly close balance on the manometer. From this point I proceeded with a normal TB balance and fine tuned with the bypass screws and cable adjustment.

 

Of course, as always, take this advice as merely something to consider. DR and Roger04RT are much more knowledgeable than I, but it is Roger's procedure I followed for my (admittedly somewhat self-inflicted) messed up TB's. :)

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If the right is not hitting the wide open tab at the same time as the left then the cables are not in sync. This would also mean your stop is incorrect on one or both throttle bodies. Unless you are absolutely certain the left side has not been touched I would go through setting the zero on that one. Best way to do this is as follows (check the TPS voltage as it is currently before starting this): 1) loosen the cable, 2) back off the stop screw until you have a gap, 3) attach a meter to pins 1 & 4 on the TPS and loosen the screws, 4) with the butterfly fully closed adjust the TPS position for close to 0mv, 5) adjust the throttle stop until the TPS reads ~130mv (I'm going from memory..............
That's putting a lot of faith in the accuracy of the pot, especially if it has been in service for a while. Film pots are not that reliable.

 

Actually I think removing the throttle bodies and critically using a flashlight to get the first glimmer of opening (plus what - maybe 1/8 turn?) is probably more accurate. These throttle bodies are so large compared to the engine displacement, that very tiny error in the opening vs pot output for whatever reason will give a lousy feedback to the emission control system at part throttle - just where you need it.

 

The the left hand TPS (plus the O2 sensor) is making the feedback and mixture pulse length determination for BOTH cylinders. Any variation in the net air opening (throttle plate plus big brass screws) of the two throttle bodies will show as a mixture discrepancy between the two cylinders since they both get the same injector pulse length. I strongly feel that is the source of surging.

 

 

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That's putting a lot of faith in the accuracy of the pot, especially if it has been in service for a while. Film pots are not that reliable.

 

That may be true, but it is the only feedback the Motronic has for throttle opening. If you go through Roger04RT's thread on this topic you'll see he went through a lot of research and found that setting the opening to give ~135mv on the TPS would give you the opening required at fully closed. I tried both methods on my '96 R1100RT and found his worked best. Trying to set both TB's visually is difficult at best and obviously the best way is to set them to flow on a bench, but most of us don't have that equipment.

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  • 3 weeks later...
If the right is not hitting the wide open tab at the same time as the left then the cables are not in sync.

 

I have heard about an old BMW rider in Germany that used to put two washers between the TB pulley and the stopping screw, one washer per side. Then go WOT and hear if the washers would fall and touch the ground at the same time.

 

If that is not a perfect sync method, I do not know what is :D

 

Dan.

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If the right is not hitting the wide open tab at the same time as the left then the cables are not in sync.

 

I have heard about an old BMW rider in Germany that used to put two washers between the TB pulley and the stopping screw, one washer per side. Then go WOT and hear if the washers would fall and touch the ground at the same time.

 

If that is not a perfect sync method, I do not know what is :D

 

 

Morning Dan

 

That is a VERY LIMITED test as it assumes the bike is perfectly level, the washers are EXACTLY the same thickness, that you can actually hear them hit the ground at the same time, that the cables take the slack up exactly the same side to side.

 

Even if the above are all met is STILL doesn't tell a person if the TB cams hit the Wide Open Stops at the same time, it only tells a person that the cams start to move at the same time for an unknown partially open position.

 

 

 

 

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If the right is not hitting the wide open tab at the same time as the left then the cables are not in sync.

 

I have heard about an old BMW rider in Germany that used to put two washers between the TB pulley and the stopping screw, one washer per side. Then go WOT and hear if the washers would fall and touch the ground at the same time.

 

If that is not a perfect sync method, I do not know what is :D

 

 

DR, you're being too logical and also seem to forget that Germans are super humans....

 

Morning Dan

 

That is a VERY LIMITED test as it assumes the bike is perfectly level, the washers are EXACTLY the same thickness, that you can actually hear them hit the ground at the same time, that the cables take the slack up exactly the same side to side.

 

Even if the above are all met is STILL doesn't tell a person if the TB cams hit the Wide Open Stops at the same time, it only tells a person that the cams start to move at the same time for an unknown partially open position.

 

 

 

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