Missing/chugging Wr450f

Hi again here are the specifications of my jets hope these help.

Main # 160s

Pilot jet # 48

Jet needle is on #4 clip position

Pilot air jet # 80

Now you will hear that you are way to lean... Same shit on my! I have rejetted, tryed different needle possisions, done the free mods and added a yoshimura slip on but the chugging is exactly at the same rpm as before I did anything. As I said earlyer, try to disconnect your TPS and I'm shure your problem is gone. I didnt notice any drop in performance by doing it and nothing wrong can happend your engine! Onroad: TPS disconnectet, offroad connected.

Hi again here are the specifications of my jets hope these help.

Main # 160s

Pilot jet # 48

Jet needle is on #4 clip position

Pilot air jet # 80

You might have to go to #3 clip. If you are lean, it will bog and not pick up speed. If it is rich it will sputter and run rough.

Where do you live here in Aust?

I just dropped from #170 main to #168 because the humidity is back over 100 here in the Northern Territory. I run all the "free" mods and a Procircuit exhaust. More airflow with the exhaust means I have to put more fuel in.

Get your self an aftermarket exhaust if you don't have one. Jetting the bike will be easier and you will turn that sheep into a wolf.

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.

James

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.

James

At last someone who understand what I have ment and what the problem is :banghead:

The Factory R&D cover is an AP cover that adjust the squirt volume of the AP circit..

Grey wire, the dealer pulled it out of the connector before I picked the bike up. This could be the ticket for you.... If you have not done this, this could be the culprit....

Dan-Thanks

All is good, well excellent. :banghead:

Did the grey wire, adjusted the float and installed 03 YZ exhaust with a Dubach S/A. Initial ride was way better than before, keep in mind the grey wire and the pipe were the only changes from before. I played around with the Zip-Ty, and viola! Think I'll get real familiar with my new freind before I venture into the YZ exh cam world. This thing is a rocket now. :banghead:

For those that still have the off idle stumble and wandering off idle, I would suggest checking the float. I found mine to be suspect, when I would just lay the bike over just a little-it would puke fuel. Thanks again. :lol::lol:

Can you tell me why I dont have the problems with tps disconnected???...

Yes, its the timing shifting. Your TPS is right on the threshold, its advancing, then coming back. Add a load or take back the load thats on it, and its gone. Unplugging the TPS just sets your timing into default, and it wont move anymore based on throttle position. So unplugging it will get rid of the problem, but you may sacrafice HP in all the others areas. I'd just live with it, now that you know what it is and drive around it if you can.

I spoke with a yamaha engineer and he told me that if the was TPS disconnectet the cdi unit read the throttle possision as fully open. He also said that disconnecting the TPS did not make any noticeable drop in performance. They have had team yamaha racebikes with TPS failure without knowing it and it had not make any difference when they repaired it...But I think the whole thing is strange. If it is like that then the cdi unit maps the ignition after rpm and fully open throttle and out of that I would think that the ignition mapping would be completely wrong down low and in the mid? But thats not the case with my bike. The only difference i notice is the chugging when tps is connected :banghead:

My wr is very snappy and strong with TPS diconnected, its hard to hold the front tyre down on mother earth under "take off" and its no problem to do wheelies by throttle in 3rd even when my ass is planted on the fueltank and not on seat :banghead:

But it was good to know what that shit was because the carb adjusting tips other guys in here told us with this "problem" to do was starting to killing me slowly.

Hi all, thanks for the very interesting reading. I just bought an 07 450f Yammy and have ridden it for the first time yesterday, on the road too. Bit sketchey on knobby tyres, but dam good fun! :worthy:

Much fiestier than the XR250 I was on! And prob even lighter!:eek:

I felt the same 1-2 second intetrval surges and knew something was up only at constant revs.

I will try disconnecting the tps plug tmrw and hope that even though mine a newer model, this will sort it!

I also not after Band-aid solution, but I am now satisfied after reading all the posts that I will also run it plugged in for O/R and disconnect for ROAD antics, cheers for all your info from Craig.

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