Wandering TPS reading. 1150gsa twin spark.

[mspenz]

Can anyone offer any advice on why my TPS reading had dropped, is it likely to just be a stretched cable on the LHS or similar?

I suppose I first noticed a slight difference after a trip to the Alps last year but it was only after getting the bike back on the road after winter that it became more obvious. I initially blamed it on dirty fuel but it continued to stall occasionally at junctions and sometimes between gears when slowing down to stop, tickover when cold was also very low even using the fast idle.
Done a motronic reset and that helped for a while but it would start the stalling with occasional splutter after 100 miles or so.


I decided to check the TPS and found that it had dropped to .26v, this is well below the parameters so was just keen to understand the reason/s why?
No knocks or adjustments to the unit previously and everything else is now as it should be and all balanced up again.



Mike.

 

[drinu64]

Maybe it was loose?

Sent from my GT-I9301I using Tapatalk

 

[buellzebub]

Set the correct value, then check again. Go for a ride and check it again. If it's changed it's probably a bad TPS. Mine went on my single spark 1150, varying all over the place. I replaced it with a second hand one and it's been fine ever since, stable voltage and runs perfectly

 

[mspenz]

Definitely wasn't loose so I'll be keeping an eye on it. Hoping to cover a few hundred miles this weekend so that should be a good test.

 

[Hay Ewe]

you could put some spots of paint / torque checker / nail paint over the screws to see if they are working loose

could also be wear on the keyed shaft that holds the butterfly, the location where the butterfly shaft slots into the TPS

 

[Roger 04 RT]

Can anyone offer any advice on why my TPS reading had dropped, is it likely to just be a stretched cable on the LHS or similar?

I suppose I first noticed a slight difference after a trip to the Alps last year but it was only after getting the bike back on the road after winter that it became more obvious. I initially blamed it on dirty fuel but it continued to stall occasionally at junctions and sometimes between gears when slowing down to stop, tickover when cold was also very low even using the fast idle.
Done a motronic reset and that helped for a while but it would start the stalling with occasional splutter after 100 miles or so.


I decided to check the TPS and found that it had dropped to .26v, this is well below the parameters so was just keen to understand the reason/s why?
No knocks or adjustments to the unit previously and everything else is now as it should be and all balanced up again.



Mike.

The throttles should rest on the throttle stop screws, if you're getting a low reading like that I would think that the stop screw is loose on that side, or not adjusted correctly.

 

[Hay Ewe]

just by chance this thread over on ADV is on the first page after a while
http://www.advrider.com/forums/showthread.php?t=996719

it may help - or it may lead you down a long winding path
read and use the information with your own caution!

 

[Roger 04 RT]

Better to start that thread here: http://www.advrider.com/forums/showpost.php?p=24838142&postcount=7, and look back at the beginning later if you're interested.

 

[mspenz]

The throttles should rest on the throttle stop screws, if you're getting a low reading like that I would think that the stop screw is loose on that side, or not adjusted correctly.

Damn, spot on!! The LHS stop screw is loose so it looks like I'll have to read up on the Lentini combined with zero=250 procedure and start from scratch

Thanks Roger, is there a link leading to a simplified process available or would it suffice to tighten the stop up as the lock nut is still firm on the screw so both nut and screw have loosened as one for whatever reason?
The TPS would obviously have to be reset again as the reading will be higher once the screw is reset or a zero=250 is performed so that's easy enough to remedy but I just need to get everything else clear in my head before starting.
I'm also hoping to head away for a few days from Friday morning and won't get much of a chance to do much before then other than just re-tightening and a TPS reset!

Mike.

 

[mspenz]

Zero=less than zero!
I've done the full reset and found that TPS zero was was backed off the scale, adjusted everything as per the instructions and set TPS to 250mV then adjusted to 350mV using the stop screw and locked down.
The RHS was balanced using Davida gauges and the stop screw and again locked in place, finally balanced at idle using the BBS screws which are now 2.25 turns out with idle at approx 1150rpm and balanced at 2000rpm by adjusting the adjuster cable...and it all works

I took it out for a run after doing the motronic reset and everything is as it should and it's running smoothly / starting easily and quickly which is good, checked the TPS again after a run and it was at 370mV but I suppose that will be due to things settling so adjusted back to 350mV when the engine was at operating temperature.
The throttle response is quite different and very even across the full range whereas before there seemed to be a bit of a powerband around 5500rpm but there is a very slight hesitation at 3000rpm although barely noticeable so I'll put some miles on and see how she goes.
Just done a motronic reset again after adjusting the TPS back to 350mV and will check that everything is still in balance after a few more runs, I was sort of dreading doing this but it was reasonably easy providing you follow all the excellent tips and instructions (thank's Roger).

Happy

Mike.

 

[Roger 04 RT]

Mike, Very glad that it worked for you. The Motronic is very sensitive to alignment errors in the low part of the band. It's very tech-y but the chart below shows just how sensitive the TPS is to errors at small throttle angles and low RPMs.

 

[mspenz]

The chart makes sense and also explains why my bike was still running well above 3000rpm through to red line!

I take it that the zero process is used regardless of cat or cat plug? My bike is running a Laser end can with y-piece and no cat code plug and had been running well until I (you) discovered the loose throttle stop screw.

Mike.

 

[Roger 04 RT]

The same process for aligning the throttle hardware on the bike to the throttle software of the Motronic applies to all Oilheads other than the chromehead, which has idle adjustment controlled by the Motronic.

 

[mspenz]

Thank's Roger, all your research and information is appreciated and my bike is running sweet

Mike.