WR450 Mods-1/8 throttle burp

[A-ron]

After reading and learning for about a month, I ordered all the necessary parts and was ready to unleash my beast. With my notebook by my side, I was able to able to follow Arins jetting tutorial to a "T". Thanks a bunch.

To my surprise, the throttle stop screw had already been cut down. Also, my airbox already had the holes punched out, and the snorkle removed. I guess my dealer did that before I was able to pick it up. Seems kinda weird that they wouldn't have mentioned it. Has this happened to anyone else?

I proceeded to disconnect the grey wire, remove the AIS, and put in a PMB insert. Then I re-jetted my bike using INDY's jetting guide. (I am at 5000 elevation riding between 65-100 degrees). For my elevation and riding temperature everything was left stock except for the needle (now using red needle 5th clip position). Bike runs great except, I now have a burp at 1/8-1/4 steady throttle. Seems to go away when accelerating, but show up again when holding the throttle steady.

Here is my question? Should I put the stock needle back in? Since that is the only change I made to the carb, and it was running well before AIS removal and tail pipe change?

Thanks for any advice, I love this place

Aaron

06 WR450

[dbailey223]

Read about disconnecting the TPS and decide if you want to do that or try to get rid of it with jetting.

[Summit]

I'm interested too. Mine does exactly the same thing and I'm at the same elevation, same mods and same jetting. I haven't messed with it thus far because it really isn't too serious. I'm rarely at 1/8 throttle and if you really twist it it's smooth.

[GCannon]

If un pluging the TPS (throttle position senser) makes the problem go away then adjust the tps per the manual. Otherwise you should be looking at adjusting the needle or pilot jet.

https://www.thumpertalk.com/forum/showthread.php?t=404614&parentpage=3

Read This.

Is your Gray wire disconnected?

[yamageezer]

I had the same problem. Try lowering your needle one position. If it gets a little better but just not enough, either adjust your fuel screw, drop the needle one more spot, or drop your pilot jet size one size. Only make one change at a time. I'm running Red #3, 45 pilot, and fuel screw 1-1/2 turns. ?

[SJMC_DON]

Tps, Tps, Tps...........

[A-ron]

either adjust your fuel screw, drop the needle one more spot, or drop your pilot jet size one size.

Are you suggesting that it is getting too much fuel? I was thinking of trying a 48 pilot jet instead of the stock 45.

A-ron

[Thumper_Bloke]

Tps, Tps, Tps...........

?

My TPS is disconnected for good now. I cant stand the way it hunts around with it connected. And i have verified my air/fuel ratio with a dyno and its perfect. The ignition mapping is farked up at part throttle.

[A-ron]

?

My TPS is disconnected for good now. I cant stand the way it hunts around with it connected. And i have verified my air/fuel ratio with a dyno and its perfect. The ignition mapping is farked up at part throttle.

What do you mean it hunts around, and what is a dyno. Do you think the part throttle mapping is farked up for both the WR and YZ? Perhaps I should re-connect the grey wire?

[Thumper_Bloke]

The symptoms for my bike were mis-firing and popping under small throttle angles (less than 1/4 throttle). "Hunting" around like surging and carrying on out the exhaust. It wasnt hurting performance, it was just make me annoyed.

A dyno- or dynamometer, can test the engines' horespower and torque, and a good dyno facility will have a tailpipe sniffer to measure the air/fuel ratio.

We changed the pilot jet to two different sizes, moved the stock needle around, and also adjusted the fuel screw. The air/fuel ratio was definately changing with these modifications, you could see it go up to 14:1 (lean) and down to 12:1(rich) on the monitor. The whole time, it was mis-firing and popping under part-throttle settings.

Finally, i disconnected the TPS and the problem dissappeared COMPLETELY.

My grey wire is still connected (stock). Pretty dissappointing the work you have to do, to get a STOCK bike to run properly. But, once you get it there, it's a great machine. ?

[yamageezer]

Are you suggesting that it is getting too much fuel? I was thinking of trying a 48 pilot jet instead of the stock 45.

A-ron

That's what I found on my bike. I e-mailed James Dean himself, and ? he got me straightened out. Now my bike rips, smoothly. I too used Indy's guide, it got me close, but you'll have to tweak your jetting to fit your bike. I tried the TPS with no success. My belief is, adjust your jetting, and I'm sure you will be successful. Be patient, it will take some work. Let us what ends up working.

[A-ron]

Time for an update. Thanks for the input so far.

So I first tried putting my stock needle back in the bike, but the stutter remained. Then I put the red needle back in...up a notch then down a notch, still no help. I have had a few people suggest trying a larger pilot jet, so I bumped my pilot from a 45 to a 48. This seemed to move the stutter higher up in the throttle position. Now it stutters closer to 1/2 throttle(right before acceleration) instead of at 1/8 to 1/4. Hmmm...

So I decided that before I screw with my jetting anymore, I should probably eliminate the possibility of a misadjusted TPS.

Off to RadioShack I went to pickup a digital multimeter for $19.99. I tested per the manual, and sure enough, the output voltage read .38 instead of being between .58-.78. I adjusted per the manual, set it at .72, and whad'ya know...the stutter is virtually eliminated. There is an extremely faint remenant of the stutter around 1/4-1/2 throttle, but I am guessing that will be taken care of when I put the 45 pilot jet back in.

So, my advice would be to adjust your TPS before you jet your bike, it can save you a few times of having to open up the carb.

WOOHOO!!!!!!!

Thanks for the TPS information you guys....

[duke2au]

HOLD IT ....STOP RIGHT THERE!!!

I too "was" a TPS conversion... Unless its broken or out of spec I why woudl you unplug it? its there because of R$D... If you didnt have one on your bike and could buy one from the parts store ..I bet you would... its a cool mod man...

ANYWAY...

Have you ever had your slide out of your carb? I put mine back upside down and it caused the exact "BURP". It leans it right out in 1/2 throttle and below. I had mine on the dyno and the stats suggested I needed a 55 Pilot, need on Clip 5, and a 170 main. TOO RICH!! (im at sea level and in australia)

the slide has the square edge down. Or you can see the letter "M" up the right way.

I put the slide back the right way and the BURP went away with TPS plugged in. Just do youself a favour and have a check...Easy Mistake

[A-ron]

I'm not even sure what the slide is...I've had the needle in and out to adjust it, and the bottom opened up to change the fuel screw and pilot jet. So I guess my answer would be NO, I have never had my slide out. Thanks for your input, though.

I'll update again as soon as I put the 45 PJ back in.

[duke2au]

I'm not even sure what the slide is...I've had the needle in and out to adjust it, and the bottom opened up to change the fuel screw and pilot jet. So I guess my answer would be NO, I have never had my slide out. Thanks for your input, though.

I'll update again as soon as I put the 45 PJ back in.

Ok, then if thats the case, get the manual and grab a multi meter and check the specs of your TPS. But make that run with out it plugged in first and see if the burp goes away.

BTW your needle is fixed in your slide assembly. It looks like a trolley type thing with four little wheels on it with a big stick thingy sticking out of it with clips on it. When you crack the nut on the trolley (aka slide) you can pull the needle out . ?

[A-ron]

Ok, then if thats the case, get the manual and grab a multi meter and check the specs of your TPS. But make that run with out it plugged in first and see if the burp goes away.

BTW your needle is fixed in your slide assembly. It looks like a trolley type thing with four little wheels on it with a big stick thingy sticking out of it with clips on it. When you crack the nut on the trolley (aka slide) you can pull the needle out . ?

I did take a test ride with the TPS unplugged, and the bike felt great...no stutter. It was then that I purchased the multimeter and adjusted the TPS.

Thanks for the tutorial on the slide...now I know I have never had that part out...only the needle that goes through the slide.

[yamageezer]

Hey ya know what, just for the hell of it, I checked my TPS voltage and mine was only .32-.34 as well, so I adjusted it to read .74 and to my amazement my bike runs smoother yet. Thanks for the info. Thats what I like about TT, you learn something new every day. ?

[TheCure]

Are you suggesting that it is getting too much fuel? I was thinking of trying a 48 pilot jet instead of the stock 45.

A-ron

that is waaaaaay toooo rich for you altitude. You need to look at somewhat leaner settings.