Throttle body adjustment gone bad. Save my summer!

Squeaky back brake? Hard to control at 30mph/40kph?
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Throttle body adjustment gone bad. Save my summer!

Post by slowdown » Tue Jul 30, 2019 1:05 am

EDIT: My bad, I meant to post this in the 1290 section, but I'll leave it up here if mods are OK with that, since some of you guys might have had this issue as well. If not OK, feel free to delete it mods.

I'm always breaking stuff on my bike, and I probably shouldn't try to work on it, but I continue to do so.

I have a '14 1290R, almost 28,000 miles. I absolutely love it. Best bike I've ever owned. I ride the piss out of it. It's my favorite thing to do. I'm really hoping I didn't kill it.

Some time in the past 10k miles or so I started noticing that my idle was hanging for a few seconds around 2250 RPM when I let off the throttle. A quick throttle blip will also make it hang for a couple seconds. After a couple seconds it would drop to 1400, which is the appropriate idle RPM. Very rarely when I'm riding I'll let off the throttle and expect some engine braking to occur as it normally does only to be surprised that the bike keeps sailing at current RPM for a second or so before starting to compression brake. It almost feels like the bike is floating. Kind of strange.

I read some threads on various sites and found this to be a relatively common issue, especially for people with the mods that I have done (Rottweiler airbox, de-cat, cannister/SAS removal, PCV, Remus midpipe and Remus can). I read a bunch of people saying that balancing the throttle bodies will fix the issue. I found a long thread on where a bunch of guys had luck bench syncing their throttle bodies.

So I tried it, and now my bike runs like complete shit.

I took off the tank and airbox to have access to the throttle bodies and the adjuster screw.

I pushed the linkage arm so that the valves were wide open (using the throttle with the bike on but not running will only move the valves 1/4 open max), and measured the distance that the front valve was open versus the rear. I adjusted the rear to try to bring its measurement closer to that of the front. The front is not adjustable. I didn't know if turning the screw clockwise would bring them closer to the same measurement, or if I needed to go counterclockwise. So I tried both and re-measured several times.

In the end this resulted in two full turns of the screw clockwise, which seemed a lot (the screw has yellow paint on it, so it's easy to know when a full revolution has occurred). The measurements had come closer together, so I put everything back together, started it up, and IT RAN LIKE SHIT. The bike was visibly shaking/juddering, it idled lower than it should, and it had this terrible resonating sound, so I killed it. I backed the screw off 1 turn and tried again, and it was still shitty, but not as bad. I decided this was no good, so I tried to put the screw back the same position it was before I started.

I put it back to where I believe is the original position, but the bike still runs worse than before. The hanging idle is gone, but the bike is running badly, and I'm not sure what to do with it. I let it idle for 10 minutes (fabled 10 min reset), and it ran a little better when warm, but on my commute today it ran like $HIT all the way home.

Idle RPM seems to drop to 1250 sometimes coming back to 1400
Engine is stumbling through 1250-3000 RPM in first gear, much worse than it ever has
Engine wants to stall when taking off out of first gear (nearly dumped me today making a left turn from a stop when it abruptly stalled halfway through the turn)
Engine will occasionally stall when giving a quick throttle blip in neutral
Strong smell of gasoline when coming to a stop
Intermittent shaking/juddering
Questionable ticking sound when engine is running
Just doesn't feel right.

If all I did was turn a single screw, and then put it back to its original position, why am I having all these issues? I guess its possible that I miscounted the number of revolutions and the screw is +1 or -1 from its original position, but I don't think that is the case.

Would hooking up a vacuum gauge to the bike and balancing that way help? I'd love to do that, but I can't figure out how to get access to the adjuster screw while the bike is running (tank/airbox are in the way) in order to make adjustments in real time. I also read somewhere (after doing it) that KTM says the throttle bodies on these bikes can't/shouldn't be mechanically adjusted (then why is there an adjuster screw?). I don't know why that would be the case, but I read it in a couple places.

I appreciate any help. I'd love to turn it over to a pro, but that's likely to get spendy, and I don't know how long they'd need to keep it.

Here's some pics/vids
Valves (little dirty right?)Image

Adjuster screw

Valve wide open

Throttle body motion with engine off: ...

Engine idle, ticking sound: ...

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Re: Throttle body adjustment gone bad. Save my summer!

Post by Winterwolf » Thu Sep 26, 2019 10:27 am

Vac gauge or hook up TuneECU to let you know what the ECU thinks each cylinder is reading would be a good starting point?

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