"sputtering" 2005 WR450

[silverlakerider]

Hey fellas, I need a little help here. My '05 WR450 has a "sputtering"/"hesitation" problem at steady throttle. It's worse when it gets warmer. When I get on the throttle it picks up fine, it just does it at constant throttle position. It almost feels like a timing issue or mapping issue. I've done all the free mods, including removing the AIS and plugging it up properly (no leaks noted.) I installed a JD jetting kit , red needle 5th from top, 168 main, all other jets stock. (I live at 4,000' elev.)

I just changed the plug (didn't look too bad but I changed it anyway.) There's no backfire upon decel nor when it "hesitates." BTW stock pipe with guts removed. It's not major, more annoying than anything. I probably wouldn't notice it too much riding dirt, but I dual sported it and I notice it on the commute (since gas is #$#%@$# expensive.)

Any suggestions would be greatly appreciated. Thanks.

[dbailey223]

You've opened a can of worms now! Just kidding. Some say it's the Throttle Position Sensor (unplug it on the street, plug it back in for dirt); others say jetting. Let the battle begin again!

[silverlakerider]

Has this sputtering topic been hashed & rehashed before? Because I couldn't find much recent threads searching.

[YamahaWR450FMike]

a 48 pilot jet that should fix the problem

[dbailey223]

Do a search for TPS or Throttle Position Sensor. The TPS has been hashed and re-hashed.

[silverlakerider]

It has the 48 pilot installed.

[silverlakerider]

Do a search for TPS or Throttle Position Sensor. The TPS has been hashed and re-hashed.

Thanks bailey. The TPS search gleaned some good info. I'm going to lower the needle 1 position and check it out. In my opinion these new FCR carbs require way too much attention for the money these bikes command. You would think you could take a bike off the showroom floor and run it.

[Numskull]

Thanks bailey. The TPS search gleaned some good info. I'm going to lower the needle 1 position and check it out. In my opinion these new FCR carbs require way too much attention for the money these bikes command. You would think you could take a bike off the showroom floor and run it.

Thats what I was thinking, I mean why in the hell do you need 50 jets Ridicules.

My '01 426 had the same problem and after all my research I thought I had it narrowed down to the pilot circuit, cause cruising speed only needs 1/8-1/4 throttle. I was gonna rejet but after I changed the timing to yz and cut the Grey wire, the stutter has disappeared

I'm still sure it was the pilot circuit, but by changing those things it changed the pilot requirements.

Have you red up on how to set the pilot screw/pilot jet?

[odonnks]

I all for a pilot jet change but the easiest is to unplug the TPS and see what happens.

[Dodjy]

I've had exactly the same problem. It was too rich in the needle. That's why it gets worse in hot weather or if you go to a higher altitude. Just lower your needle 1 groove (raise the clip) and leave the tps connected.

[silverlakerider]

Have you red up on how to set the pilot screw/pilot jet?

No I haven't

[Numskull]

No I haven't

Heres the link. You will need the zipty fuel screw, or make your self one so you can adjust it as its pretty hard to reach.

https://www.thumpertalk.com/forum/showthread.php?t=327405

Goodluck

[silverlakerider]

I've had exactly the same problem. It was too rich in the needle. That's why it gets worse in hot weather or if you go to a higher altitude. Just lower your needle 1 groove (raise the clip) and leave the tps connected.

Thanks Dodjy. That's exactly what I did and it's a lot better. I rode the bike to work last night and it only "sputtered" 2 or 3 times, briefly each time. I'd say it's running about 98% good. So here's the end result- This time of year where I live it's mid 80's during the day and mid 40's at night, no humidity and elev. is 4000' msl. I'm running a 168 main, JD Red #4, 45 Pilot, 1.5 turns, 65 starter jet, #50 leak jet. I never did disconnect the TPS - to me it doesn't make sense, it's there for a reason. This problem is caused by jetting and not the TPS sensor, plain and simple. To totally cure the sputtering and try and make the bike 100%, today I'm going to install a 48 pilot and report back. (Sorry yamaha mike, I brainfarted and thought it had a 48 pilot inst.) Just one more thing to buy for this bike. And after spending $70 on a JD kit you'd think it would have a couple of pilots and maybe even leak jet or two that come with the kit. I'll let you all know tomorrow how the new pilot works.

[joshbeene]

I had that exacty same problem. I bought the GYTR (Yamaha) smog block off kit which comes with a new needle, pilot, and main jet. Once I changed out that stuff my bike really came alive. Before I put it in the bike would not like to hold a constant RPM. It would act like it was cutting out or hesitating, but once I put in the new jets it works great. It was the best $40 I have spent in a long time. Let me know if you have questions about putting it in.

[silverlakerider]

Well fellas, finally got it right today. At least now I can rip apart my bike, spin my carb, change jets and put it back together and test it out in 20 mins. I changed to the 48 pilot today and it made it worse. So now I know for sure that the hesitation problem is being too rich and the problem is definetely caused by jetting-NOT TPS! Here's the final specs: 165 Main, JD red #4, 45 pilot, 1.5 turns out, starter and leak jets stock. For the new buyers out there (in my own opinion) don't waste your money on the JD kit. Buy the GYTR kit direct from yamaha or a dealer, it comes with all the needed jets, (not just mains like the JD kit) a new needle, and smog blockoff kit. You'll save money and time in the long run. Now it's time to enjoy my bike instead of tinkering everyday -time to cut the lawn!

[Ballinator]

I have an 03 WR450 and this stuttering problem has been bugging me for 10 years. I recently installed a Tinytach. I had to set it for multiple sparks per revolution to get it to read the correct rpm's. That tells me tht the ignition fires more than once. Now check this out. When the RPM's reach arround 3000 RPM and above, the reading on the Tinytach reads half the number. ie 1500 RPM.. I think that the CDI changes from 4 sparks to 2 per fire. Oddly enough, thats the RPM range that the stutter happens. I think the CDI is changing from 4 to 2 fires and if we are cruizing at that rpm its cutting in and out of two differnt modes resulting in the stutter.