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dvfh

Please Help! 04 WR450 bogging out at half throttle.

17 posts in this topic

Problem. I get about half throttle and the bike just bogs out. I thought it may be a carb problem. So, I figured out take out the carb and clean out the float bowel. I order new jets from baja, because everyone else says it runs to lean stock. So, I got their jetting kit and muffler insert. Took of the carb and cleaned it out and replaced with new jets. However, I did not find anything in the float bowel. Sprayed it out with compressed air, replaced the jets but found no foreign matter. I was hoping to find the culprit staring me right in the face, so I could put everything back together with confidence. Now that I did not find a shred of evidence to support my original theory (any foreign object in the float bowl or the jets I replaced) I am worried I missed something or my original diagnosis was incorrect. I put everything back together and there is still a bogging out problem at about half throttle. Could it be electrical? Maybe a loose wire? Any ideas?

The fuel screw is turned out 2-1/4 turns. 48 on the pilot jet and 160 on the main jet. I live in MD, so at sea level or so. All other jetting is stock. Baja says this should be perfect. Although, I am not convinced it is the carb. Unless I missed something in the carb someplace other the float bowel or the pilor or main jet, since both are brand new.

dave

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Put in a 165 main, stock needle clip #5 from the top, 48 pilot, 72 starter jet, 48 pilot jet, #40 leak jet, adjustable zip ty fuel screw ( Recommend JD jetting kit with blue needle in clip #4) . Set your idle on the high side. That should eliminate the bog and you should be able to wheelie from idle in first gear by cracking the throttle as quick and hard as you can. :cry:

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The fuel screw is turned out 2-1/4 turns. 48 on the pilot jet and 160 on the main jet. I live in MD, so at sea level or so. All other jetting is stock. Baja says this should be perfect. Although, I am not convinced it is the carb. Unless I missed something in the carb someplace other the float bowel or the pilor or main jet, since both are brand new.

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Put in a 165 main, stock needle clip #5 from the top, 48 pilot, 72 starter jet, 48 pilot jet, #40 leak jet, adjustable zip ty fuel screw ( Recommend JD jetting kit with blue needle in clip #4) . Set your idle on the high side. That should eliminate the bog and you should be able to wheelie from idle in first gear by cracking the throttle as quick and hard as you can. :cry:

Make sure you raise your needle! Richer jetting is needed at the needle. :cry:

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Fuel screw sounds as if it is about max out, I would agree with Indy and raise your needle one clip position and then turn your fuel screw in to something closer 2 turns.

The problem with jetting is there are so many varibles like altitude and humidity that one setting may work for one person may not work for another, another words just because Baja says it should work doesnt mean it will.

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Definitely raise the needle one clip position. With winter and cooler temperatures everybodys bikes are going lean out a bit. 1/2 throttle is dead center in the needle so I would agree to start there. If it is still acting up maybe increase your main up a size to a 162 or 165 to help the needle a bit more and richen the last bit of throttle.

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The fuel screw is turned out 2-1/4 turns. 48 on the pilot jet and 160 on the main jet. I live in MD, so at sea level or so. All other jetting is stock. Baja says this should be perfect. Although, I am not convinced it is the carb. Unless I missed something in the carb someplace other the float bowel or the pilor or main jet, since both are brand new.

What severity is the bogging? Does it feel like it could maybe give you a little more juice, or like it's going to stall... or somewhere in between?

I ask because your current setup, though it leaves something to be desired, is not bad enough to cause even moderate "bogging", especially if this is a new condition.

If it is a new condition, or you are experiencing moderate to heavy bogging, jetting won't get you anywhere (though you should follow Indy's advice either way).

Our of spec valve clearances have done stranger things... Just a thought.

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Thanks for the questions. Yea, I don't think it is carb related anymore. It runs great except for at half throttle, then it just won't go past and boggs out at half throttle period. I would say severe. It just sputters right there like it is going to stall, just keeps sputtering. When I let of the throttle it runs normally agian.

So, you think it could be a stuck valve or valve relaed? I just don't think it is the carb and something like that would make more sense. Does it sound like a valve problem? Could it be the stator? I sent it into baja for the dual sport kit but it ran fine for 50 miles or so. Thanks for the advise, I am at a loss.

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Stator rewound? may be faulty? maybe something to do with current getting to the CDI? either too low or Hi? messing up the CDI? maybe someone with electronic experience can say whether this could be happening.

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I personally have not done this, but heaps of guys from here have. I would disconnect your TPS sensor. This should remove the CDI from the equation. Therefore fault finding by eleimination.

ps

Guys on 450's tend to leave tps disconnected as it apparently runs smoother at 1/4 to 1/2 throttle

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Dave,

Just sent you a PM. It sounds like a possible TPS issue if you're experiencing this on the street at constant steady throttle. My bike was horrible on the street until I disconnected it..

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It is most likely caburation. If it pulls strong up top and down low how can it be a valve problem? :cry:

Everyone was giving him jetting advice, and my questions were to determine if the problem was related to jetting. I would say from his response (severe bogging, new condition) that the problem is obviously unrelated to tuning the jets.

I agree that it is probably carburation. I would pull the carb back off and look at the needle/main jets and check the fuel supply. Consider the condition of the air filter (too much oil?). Put a 165 main in at the same time, but don't expect it to fix your problem.

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Thank Dave,

I am not sure what else to do. As I said I cleand out the float bowl and nothing. I can try again and see. What is the TPS? What does it do it? where is it? Thanks again.

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You have to jet the bike right before you do anything drastic. All WR450's have a bog (flat spot) with poor jetting. :cry: Get the JD jetting kit and run the Blue needle in clip #4 or #5 from the top. Run a 170 or 165 main for colder weather we are having now. Buy a #40 leak jet and put it in the bottom of your float bowl (stock is a #70) 48 pilot is good. Have you cut your gray wire? If not do so. Then let us know the results. :cry:

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your Throttle Position Sensor is an electronic sensor mounted on the top left of your carb. this unit sends info to you cdi to detemine and smooth out timing advance. or something like that. unscrew this lead and see if the problem persists. good diagnostic.

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