[MushroomMotors]

So I’ve been riding my R6 for a few years now and I’m used to the heavy engine braking that comes when you close the throttle all the way. Just the other day I noticed that the RPMS tend to “hang” when I close the throttle. If I rev It to 7k for example and let go of throttle it typically would slow rapidly back down to idle. HOWEVER as of yesterday when I rev up the bike the rpms hang for a split second longer than usual and take a noticeable amount of time to return to idle and the bike kinda coasts a lot farther than it ever would before. My throttle and cable is free and there’s nothing amiss there, I checked operation a couple of times and it snaps closed nicely. I’m thinking I may need to perform a leak down test because most of the research I’ve done pushes me towards a lean air/fuel mix. But I’m hoping someone with a little more mechanical experience could help me save some money, time and frustration. Another puzzling aspect of this issue is that after messing with it for awhile I’ve noticed that the issue isn’t there in neutral???? I can Rev the bike up and rpms drop normally, it’s only when the bike is in gear….Also if I’m in 1st gear and I give it throttle and immediately engage the clutch the rpms drop rapidly like I’m used to. I dont seem to have any power loss but it’s a strange sensation having the bike coast so far while still being in gear and it has affected my confidence in cornering heavily. Would love any and all advice relating to this before I start buying tools parts or taking her to the shop. Many thanks, Mushroom

 

[8Ball]

If your bike is an R6 (not an R6S), the throttle cable is not connected to the throttle plates on your bike. You know that right? Check the operation of the throttle servo that runs the throttle plates. You may need to clean the throttle mechanism.

 

[MushroomMotors]

R6

youtube.com

I did the plugs/coils and fixed a misfire a few months ago, noticed my cable was off the bracket and fixed that then. This is a video showing the mechanism it doesn’t seem to be a servo but I’m somewhat new to motorcycle mechanics so let me know what you think? But it sounds like it’s snapping back freely with just a little freeplay but much quicker than the bike “revs down” so to speak. It’s a strange sensation having the r6 go from one day strong engine braking to almost none, you coast so much further than expected but the throttle feels shut all the way.

 

[8Ball]

I can’t tell anything from that 2 second video. But you have a cable that is connected to a throttle position sensor. That feeds a signal to the ECU. The ECU sends a signal to a servo motor (located in the other side of the bike) and that servo motor opens the throttle plates. The system is fly-by-wire. Your issue is probably on the servo mechanism

 

[Intuit]

Vacuum should spike when the throttle is closed.

Vacuum Gauge Tutorial www.secondchancegarage.com Adobe Flash Player

www.secondchancegarage.com-public-186.cfm.mp4

1drv.ms

Any exhaust or tuning changes could trigger a change.
I have the previous generation (no servo) but are able to affect engine brake via tuning.
Because it doesn't light-up the rear, have to be mindful of how much and when you engine brake. That may catch vehicles behind you off guard.

 

[MushroomMotors]

I can’t tell anything from that 2 second video. But you have a cable that is connected to a throttle position sensor. That feeds a signal to the ECU. The ECU sends a signal to a servo motor (located in the other side of the bike) and that servo motor opens the throttle plates. The system is fly-by-wire. Your issue is probably on the servo mechanism

Would my diag mode show issues with 01,13,14,15 If the servo motor was bad?

 

[MushroomMotors]

Would my diag mode show issues with 01,13,14,15 If the servo motor was bad?

All values were between 16-17 and 100-101

 

[8Ball]

You want to run diag 01 and 13. But it doesn’t sound like the values are the problem. The mechanism is may be hanging up or closing slowly. You need to actually watch it to be sure it’s operating smoothly. If it is, you may have a vacuum leak. (Hose loose or throttle bodies not seated all the way)

 

[MushroomMotors]

You want to run diag 01 and 13. But it doesn’t sound like the values are the problem. The mechanism is may be hanging up or closing slowly. You need to actually watch it to be sure it’s operating smoothly. If it is, you may have a vacuum leak. (Hose loose or throttle bodies not seated all the way)

Thank you for your help! I’m thinking the latter but I figured try to get advice before I open her up again. Any thoughts on the carb cleaner trick to isolate the vacuum leak? Most videos I can find are carbed and not EFI so I’m not too sure the best places to spray yet

 

[8Ball]

Same place. Around the boots where the TBs are connected to the engine. And around the hoses

 

[Wheelz96]

I would start at the clamps holding down your throttle bodies. This definitely sounds like a vacuum leak. Pull tank, check tb clamps, all vacuum lines, and then if problem persists, you may find a hose is cut somewhere.

Full disclosure, vacuum leaks can be annoying to trace down but carb clean trick certainly helps!

 

[mordantly]

Engine revs raise substantially when you spray the leak, but it sometimes only gets close to actual crack. So use your eyes and examine all around where you sprayed that increased the engine rpm.