RPM fluctuation and surging

motolink

Nitrous
Joined
Sep 11, 2010
Messages
1,421
Location
Brisbane South, Australia
Ride
2011 Roadster and 2001 Bonneville
I have been experiencing surging on constant throttle from about 2000rpm and above. When parked, in natural and holding the throttle fixed on 2000 RPM the RPM will fluctuate up and back by 200 RPM. From about 1800 RPM it is very difficult to hold the RPM stable on a fixed RPM. This is the same sort of surging I feel when cruising and worse when I engage the MCCRUISE cruise control.
I have replaced the spark plugs, replaced the fuel filter, tightened the low tension wires on the coils, sprayed some WD40 around trying find any vacuum leaks. cleaned and lubed all the throttle linkages but no change.
2011 Roadster 47400km.
Any suggestions of what I should look for.
 

motolink

Nitrous
Thread starter
Joined
Sep 11, 2010
Messages
1,421
Location
Brisbane South, Australia
Ride
2011 Roadster and 2001 Bonneville
I checked the TPS voltage, it was reading the voltage I set it some time ago and then each time checked it was a different reading so took it off. See the photo of one I took off and the one I purchased from the local Triumph dealer. Both have the blue inside the portion that goes into the throttle body.
I like remove the Stepper Motor to clean it up and check it as well, how difficult is this to do.
EF1D9134-7A95-4226-9026-51A424C307E6.jpeg
 

bebsy

Finicky
Joined
Mar 18, 2017
Messages
211
Location
Pattya Thailand
Ride
2006 Triumph R3
I had that horrible surge at 3000rpm always felt like ringing its neck when it happened most annoying and dangerous, anyhow to cut the story short turned out it was a flat spot on the tps and throttle bodies out of synk, if your replacing with a new tps and the tolerance on the stepper is correct and the numbers on tps tally up.. Then you'd need to be looking elsewhere, you can get a visual on the stepper motors function in situ, and go from there I'd jus give the stepper springs and all else a good squirt of good old WD40,
 

1K9

Big Cruisers 4 Me
Joined
May 24, 2016
Messages
3,802
Location
Clear Lake / Houston, Texas
Ride
2007 Rocket III
Had the surge blues for a while on my 2007 Classic. Several folk tried to fix it. Finally, Rob (Mufasa) took the stepper off the idle chain. Butterflies came off the throttle body too. Fixed the bike for good.

A quick check for this problem... just disconnect the stepper motor. You will need to throttle the bike manually like in the old days. Once the bike warms up a little it should idle. Go ride and see if this fixes the idle issue.

Change and calibrate the TPS. If it's still bad it might be the linkage arm of the stepper binding or a bad stepper motor. If it's not that I have no more suggestion. Also changed the MAP as well as remove and lube the vacuum hose tips and nipples with no effect. Eventually took the action arm from the stepper off and reconnected the stepper to get rid of the check engine light. Main idle was adjusted mechanically. Not going back to the stepper set up. The bike is hard to start sometimes but runs and idles well now.
 
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motolink

Nitrous
Thread starter
Joined
Sep 11, 2010
Messages
1,421
Location
Brisbane South, Australia
Ride
2011 Roadster and 2001 Bonneville
Thanks for the input, I am going to fir the new TPS and see if that changes the surging. I don’t have have any idle issues on the surging above about 1800RPM. Is there any way of bench testing the TPS and the stepper motor.
How would the stepper motor affect the running of the motor at 1800 RPM and higher, I thought it only came into play on start up and control the idle speed.
 
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bebsy

Finicky
Joined
Mar 18, 2017
Messages
211
Location
Pattya Thailand
Ride
2006 Triumph R3
Thanks for the input, I am going to fir the new TPS and see if that changes the surging. I don’t have have any idle issues on the surging above about 1800RPM. Is there any way of bench testing the TPS and the stepper motor.
How would the stepper motor affect the running of the motor at 1800 RPM and higher, I thought it only came into play on start up and control the idle speed.
As you suggested the idle steppers job is just that, you can run your tps slowly through its full range of motion checking voltage on tune ecu, or better still the old one while it's installed on the bike, as the other folk suggest my money is on that tps🤞, what totally smoothed my ride out low down was fitting bigger headers that could have been down to the tune I was using with stock ones not being able to get rid of the spent gas efficiently was my thought🤔
 

1K9

Big Cruisers 4 Me
Joined
May 24, 2016
Messages
3,802
Location
Clear Lake / Houston, Texas
Ride
2007 Rocket III
Thanks for the input, I am going to fir the new TPS and see if that changes the surging. I don’t have have any idle issues on the surging above about 1800RPM. Is there any way of bench testing the TPS and the stepper motor.
How would the stepper motor affect the running of the motor at 1800 RPM and higher, I thought it only came into play on start up and control the idle speed.
The rocket motor is cooking at 2000 rpm. Get TUNE ECU and a LoneTech cable and adjust your throttle bodies, TPS and adaptations. Get a 7 mill spanner wrench (in think that is the size) to adjust the stepper voltage nut and a set of short star screw drivers to adjust the TPS. The bike will like it. Also get a long flat screw driver the adjust the bodies. aaahhh and remove all the air ducts and install a RamAir filter. Little money well spent.

In my opinion excessive lubing attracts dirt. The only binding I have seen is in the spindle where the action arm from the stepper to the bodies rotates. I took mine off and run without it just fine.
 
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