Bucking At Constant Speed


17 replies to this topic
  • bobpara

Posted September 26, 2014 - 12:41 PM

#1

When I'm cruising along at a steady throttle position  ie, not accelerating or decelerating

the bike kind of lurches like its about to run out of gas or something

Turn the gas on, or slow down and it goes away.

I seem to remember seeing a thread about this in the past

 

Why does this happen and is it easy to cure?

 



  • revelc

Posted September 26, 2014 - 12:42 PM

#2

Tps?


2014 WRR-R.I.Pieces
2012 WR450F-Stolen

  • William1

Posted September 26, 2014 - 12:45 PM

#3

How many RPM? Under 5K?

 

Drive line snatch will do it. Too loose a chain, worn out chain makes it worse.



  • bobpara

Posted September 30, 2014 - 06:15 AM

#4

Sprockets & chain 2 mos old and adjusted to spec.....doubt it an issue

Somebody said TPS....I assume you have one of these with FI

Mine is an 06 with a carb, I dont have one

 

Its like a surging or bucking at steady state

....I seem to remember a posting about this


On the throttle or off the throttle, no problem

Its most noticable when you drive down a wide open road and try to maintain any constant speed



  • motoxvet

Posted September 30, 2014 - 06:19 AM

#5

Are you POSITIVE that when this is going on, when it's lurching., the throttle is NOT moving, even the slightest amount?



  • William1

Posted September 30, 2014 - 06:28 AM

#6

Sounds to me like the OP needs to downshift and run a lower gear.



  • bobpara

Posted September 30, 2014 - 10:26 AM

#7

I guess I do have a TPS! An odd design, the first I've seen this way

It looks like your basic potentiometer; a wiper and a carbon track resistor kind of like a rheostat

There could be alot of wear on the pot esp the mid-throttle where the throttle spends most of its time

I could bring the revs up real high (and constant) or real low and constant and see if the problem goes away

 

Any idea why on pg 6-20 they say: "Do not loosen the screws of the TPS except when changing the TPS due to failure because it will cause a drop in performance"

.....On pg 6-22 they talk about adjusting the output voltage by adjusting the physical position of the sensor

Are they trying to prevent you from knocking it out of whack or is there something else I am missing



  • William1

Posted September 30, 2014 - 10:33 AM

#8

If you think the TPS is causing a problem, unplug it at the harness and ride the bike. You'll loose a little power but if it is sending a poor signal, by disconnecting it, you know.

TPS along with engine rpm and the trans gear indicator tell the ECU what timing variations to make.

You should not remove the TPS because if you do, you have to reset it and that can be touchy. The manual expalins the procedure for eletrical tests and adjustment. If you do not ever remove the TPS, it never needs to be touched unless it fails. TPS have been on bikes over 20 years. Nearly ever 4S MX has always had one, many 2S do too.

 

It sounds to me like you are over analyzing this and may well 'dig yourself a hole in the wrong part of the yard'

 

Try downshifting and ride in a lower gear.



  • RHeritage

Posted September 30, 2014 - 07:47 PM

#9

Sorry guys, downshifting due to lugging is not the issue. I have the same exact problem on my 04, constant speed in top gear 50 or 60 mph seems to miss a bit . Thought it might be drive line issues, just installed new sprockets and chain, same issue.  Bike has been uncorked, grey wire mod etc... Spark Plug is good, carb is clean. Tried changing jets and needle from stock to JD kit, same issue, really annoying. Did not notice the issue until a few street rides, off road I was moving the throttle enough if was not noticeable. Anyone that has experienced same exact conditions I would appreciate your resolution, constructive replies appreciated.

 

Rich



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  • revelc

Posted October 01, 2014 - 01:39 AM

#10

Sorry guys, downshifting due to lugging is not the issue. I have the same exact problem on my 04, constant speed in top gear 50 or 60 mph seems to miss a bit . Thought it might be drive line issues, just installed new sprockets and chain, same issue. Bike has been uncorked, grey wire mod etc... Spark Plug is good, carb is clean. Tried changing jets and needle from stock to JD kit, same issue, really annoying. Did not notice the issue until a few street rides, off road I was moving the throttle enough if was not noticeable. Anyone that has experienced same exact conditions I would appreciate your resolution, constructive replies appreciated.

Rich


Unplug TPS first.


2014 WRR-R.I.Pieces
2012 WR450F-Stolen

  • DunmireD001

Posted October 01, 2014 - 03:22 AM

#11

Sounds like you need 1 size bigger main jet. Sounds like as your giving the bike throttle (fuel) steadily, it is not getting quite enough fuel. It's obviously enough to make the bike run, but at a constant 70% throttle pull, maybe it could use a slightly bigger jet just to give it that little extra. Or you could maybe adjust your carb to run slightly richer. Also check your spark plug. If it's toast, that could also explain it.

  • stevethe

Posted October 01, 2014 - 06:03 AM

#12

Sounds like this http://www.thumperta...ter-gone/page-3



  • revelc

Posted October 01, 2014 - 04:40 PM

#13

BTW this subject is in the FAQ sticky.


2014 WRR-R.I.Pieces
2012 WR450F-Stolen

  • RHeritage

Posted October 01, 2014 - 06:33 PM

#14

revelc,

 

Found it on the FAQ page, thanks, I'll try disconnecting and running at speed see what happens. I think this this is the culprit.

 

Rich



  • William1

Posted October 02, 2014 - 11:22 AM

#15

A 'stutter' is nothing like 'bucking'. No more than a 'girl' is a 'hot chick'. Very different definitions.

 

The infamous 'WR Stutter' happens in all gears at steady mid throttle.



  • greenhammer75

Posted October 26, 2014 - 10:02 PM

#16

Disconnect the tps and ride.

  • sherco67

Posted November 03, 2014 - 05:43 PM

#17

Mine also on the road at steady rpm, got a good deal on a Vortex ignition, along with the map switch as a plus, and is a carb. model 09, one of the best mods done to date. http://www.vortexcdi...l=35&mp_id=1262



  • Jon E

Posted November 05, 2014 - 12:24 AM

#18

If you think the TPS is causing a problem, unplug it at the harness and ride the bike. You'll loose a little power but if it is sending a poor signal, by disconnecting it, you know.

TPS along with engine rpm and the trans gear indicator tell the ECU what timing variations to make.

You should not remove the TPS because if you do, you have to reset it and that can be touchy. The manual expalins the procedure for eletrical tests and adjustment. If you do not ever remove the TPS, it never needs to be touched unless it fails. TPS have been on bikes over 20 years. Nearly ever 4S MX has always had one, many 2S do too.

 

It sounds to me like you are over analyzing this and may well 'dig yourself a hole in the wrong part of the yard'

 

Try downshifting and ride in a lower gear.

"Try downshifting and ride in a lower gir.". That works perfect for me, try it! All other tips failed, exept TPS helped slightly. I commute to work every day, and just live with the fact that this bike is not made for road use. Just shift to a lower gir :-)






 
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