03 Yamaha WR 450 hiccup

Need Help Have the straight mods, air box, gray wire,throttle stop,exhaust, Ran great for months. Now from low rpm if you crack the throttle it falls on its face, then hang on

I can't help you with so few indications. There would be a lot of reasons for this problem. You have to check: spark-plug, fuel on the carb, cleaning of the carb and air filter, the breather on the tank.

Just two week ago a friend of mine had this kind of problem. Before to start the ride, we fill up the tank of uor bike (my friend's bike is a WR 250 '95). After 3 minuts the bike starts to hiccup. We had spent a lot of time to found the problem, then we found out that closing the tank plug, the breather tube was twine, so the breather didn't work. :)

You might try JD jetting kit (blue needle) for the cooler less humid weather. Mine was about the way I like it then it started to cut-out midway as the temp and hum fell. :)

Several things.

1) Did you do something to your carb? If so you may have assembled it wrong, the plate on the slide can go in both ways but only 1 way is right.

2)Your plug may be fried, try a new plug.

3)Your fuel may be contaminated. Maybe a little water in your fuel bowl. Drain your carb, I would do it by removing the access on the bottom of the carb. and check to see if there is stuff sitting in it.

4) You have gotten gunk in your carb and it needs to be cleaned.

5)Fuel flow problem, as suggested in other post.

6) your valves are out of adjustment and need to be checked.

Just some of the ideas I have thought of, good luck, and let the rest of us know what you do to correct the problem.


Try the accelerator pump. They are finicky. Clean it out and reinstall it. Pay attention to the original setting. Then install an inline filter.

Good Luck

Your post doesn't say where you are from----did it start getting cold lately?---running too lean?---does the fuel screw make any difference if you turn it one way or the other? :)

Definitely try adjusting the fuel screw first once the bike is WARM.

Bring the idle up to about 1700rpm,then adjust the fuel screw.When it is adjusted properly the idle will pick up and it will respond well when the throttle is whacked open.

If your final setting is between 1 and 2.5 turns from being fully seated your go to go. If less than 1 turn then go to smaller pilot jet, if more than 2.5 turns out from seated position then go to a larger pilot jet.

Most likely you'll need a larger pilot jet, due to the onset of cooler temps. this time of year youll need to richen the circuit. You may need to raise the clip 1 position, and go up on the main as well. :)

The owners manual has some pretty good info to help you out, and explains the different circuits pretty well.

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