TPS voltage

[Mark K]

Just did a full tune-up a week or two ago (plugs, valves, sync, etc) which eliminated the buzz in the bars, and maybe I should have left it at that; but when I checked the TPS voltage on a whim this AM, I found it to be at .498. I reset this to .385 using only the rotation in the sensor -- I did not touch the stop screw, nor anything else. Well, I take that last part back -- I removed Fuse #5 for a reset. I haven't taken it out for a spin yet, but I have noticed a smoother idle (my initial impression -- could also be my imagination).

 

Question 1: Could this explain the backfire/afterfire I experience upon deceleration?

 

Question 2: Do I now need to redo my TB sync?

 

 

Thanks in advance!

Mark

[smiller]

Question 1: Could this explain the backfire/afterfire I experience upon deceleration?

Yes.

 

Question 2: Do I now need to redo my TB sync?

No, or at least not as a result of resetting the TPS.

[bmwmick]

Question 1: Could this explain the backfire/afterfire I experience upon deceleration?

 

Thanks in advance!

Mark

 

Mark,

To expand on what Seth said, with your TPS at .498, the Motronic was NEVER seeing a "throttle closed" condition (.400V or under) and on trailing throttle it would NOT shut off the fuel injectors. That can dump some raw fuel in the exhaust and cause popping.

Above 2,000 RPM on trailing throttle, you should be able to tell the difference. There will be just this slight hint of a little jerk as you cross the 2,000 RPM mark decelerating and the injectors come back on. Almost imperceptible but it's there now I'll bet.

 

Mick

[T__]

Mark, you have good information above on what could IF it was that high.. .498 seems awful high if the factory paint marks were still lined up.. You didn't by chance set that TPS with the choke (fast idle) on the first notch or a slightly hanging throttle cable did you?. Not trying to question your work, just adding a possibility here..

 

Twisty

[Mark K]

Thanks for the replies, fellas. Glad to hear amout not having to re-sync. Interesting about the raw fuel. I would occasionally get a whiff after pulling into the garage. I've also had a drop or two come out of the vents behind my right footpeg. Noting bad, or even repeatable. I attributed it to it not having an evaporative cannister.

 

Also re-checked voltage again just now -- .389 repeated several times after blipping the throttle. There are/were no paint marks on the sensor and/or fasteners. I have never meddled with it myself. Makes me think back two or three years, though, when I had an issue about idle speed. Bike ran rough at idle and would occasionally die. Local dealer had it for two weeks and told me they ended up replacing the O2 sensor. Perhaps they also tinkered with the TPS to force a richer fuel mix at idle. Needless to say, I've been doing my own service ever since.

 

Interesting information about the Motronic never shutting down the injectors......Mick (or others), with the Motronic never "seeing" closed throttle before, I can't see how my idle sync isn't screwed up.

[smiller]

I've also had a drop or two come out of the vents behind my right footpeg. Noting bad, or even repeatable. I attributed it to it not having an evaporative cannister.

Yes, that's correct. With the canister removed you are venting the tank directly to the atmosphere and sometimes fuel can condense in the line resulting in a few drops on the ground. This has nothing to do with the TPS setting.

 

with the Motronic never "seeing" closed throttle before, I can't see how my idle sync isn't screwed up.

The TPS only measures the throttle position on one cylinder so it doesn't have any effect on the synchronization between the two cylinders. The TPS doesn't even know what the other cylinder is doing... it just assumes that the throttles are synchonized and that both throttle positions are the same.

 

BTW if you're thinking that this isn't a very good design then you're right, and in fact the FI system was upgraded in the hexhead bikes with a TPS installed on both throttle bodies instead of just one.

[Ken H.]

BTW if you're thinking that this isn't a very good design then you're right, and in fact the FI system was upgraded in the hexhead bikes with a TPS installed on both throttle bodies instead of just one.

Sorry, not true. The R1200xx "hexhead" series still only has a TPS on the left side.

[smiller]

Sorry, not true. The R1200xx "hexhead" series still only has a TPS on the left side.

Ooops, yes, I was confusing the stepper motors with the TPS. Thanks for the correction.

[Mark K]

No need to sync again? Cool!

 

It sounds like between this little change and the new shocks I have coming, I'm going to have to relearn how to pilot this machine!

 

Thanks again, everyone!