AFAIK, the TPS is a variable resistor...just reading the adjustment procedure tells me that...you're adjusting the TPS voltage. It's easy to check, just unplug the tps, connect an ohmmeter and twist the throttle...
The TPS on our bikes are about the same as passenger cars. I suspect ours is like the earlier design (single pole, double throw switch (SPDT) and it operates where there is one common input and 2 other contacts, one set is closed at idle, the other set is closed at wide open throttle, and both are open anywhere in between. I doubt we have the high tech linear types by the way the timing is jumping.
Med/high speed hiccup on 04' WR450
Posted October 04, 2005 - 12:55 PM
Posted October 05, 2005 - 06:45 AM
So.... I guess the best and only solution is to RIDE FASTER! Or unplug the TPS wire, depending on what type of riding you'd be doing.
Im really glad to know that we have a lot of smart and helpful people in the Yamaha forum.
Posted October 07, 2005 - 12:16 PM
Posted October 07, 2005 - 01:42 PM
I've had many, many jetting dialogues with WR owners on the light throttle steady speed stutter problem. It's a Yamaha issue and most noticeable on WR400-450's and WR250's.
---Disconnecting the TPS is the only consistent answer. Disconnecting the ACV and different jetting doesn't normally solve the issue. The condition seems worst on flat, paved road at a steady speed of 30-50mph.
The condition should not be confused with overly rich jetting causing a sputter and miss, or lean jetting causing a lag or bog. Work to refine the jetting carefully and the condition will only be found at a steady mid-throttle cruise.
Posted October 11, 2005 - 10:25 PM
Posted October 12, 2005 - 02:53 AM
So I think there must be a solution whith jetting without disabling the TPS.
But additionnaly I also think ther is a big difference on the Euopean and US WRs ( grey wire does no affect, jetting seems to be leaner?)
Hope one fine day the jetting will be perfect or Yam will switch to injection :-)
Posted October 12, 2005 - 05:29 AM
jd jetting is pretty much getting close to spot on
the tps is good for the dirt, but will cause the stutter at constant rpm in 5th
by the way i have a 99 wrf, i have the stutter, so its not the CDI, the only other thing that may differ in the wiring harness is a short, which would prob cause the bike to run bad or not at all, and the regulator is different, i think it was the 426s that got the upgraded regulator/rectifier
the wr400 is only regulated NOT rectified, the whole system runs on AC
Posted October 12, 2005 - 07:47 AM
...the studder has nearly gone. There is only a very small studder when cruising on higher speed (about 60mph)
This is the usual result after many attempts with rejetting. The steady speed, light throttle stutter can be reduced, but not eliminated by adjusting the carburetor. The same annoying symptoms were on my '00 WR400 and '03 WR250, but I didn't ride them on roads enough to care about it.
Posted October 12, 2005 - 08:42 AM
....I didn't ride them on roads enough to care about it
I am normaly not riding like this, but I will start to a desert rallye in a few weeks and there will be some connecting stages onroad
Do you have any ideas how to jet with jd kit that comes nearest to Yamahas stock jetting. I noticed a smoother accel with JD needle that I would get again
Posted October 12, 2005 - 11:51 AM
Posted May 11, 2013 - 09:17 AM
but mid to hi rpm it starts to bog but it goes away if i nail the throttle, i have a jet kit and adjustble needle jet. was wondering because this bike sat for a year in a gurage, b4 i take the carb out i want to see if C-foam will cure it.
any help would be great.