kicking way to often

I just purchased a 03 yz450. I ride a lot of trails and ride some mx. I took the bike out today for the first time and loved the power. Its strong and consistant and will also rev to outerspace. The problem is stalling. The bike kept dieing after letting off at low rpms. I just read about the accelerator pump and was thinking that I may be flooding it as i like to blip the throttle often. But even then it seems that it shouldnt die so often. I am new to fourstrokes and i was wondering if the stalling problem was rider error or a jetting /adjustment problem. I am ridding again tomarrow so if anyone who reads this has a suggestion I would like to hear it, otherwise I going to take it in for repair or adjustments on monday.


By the way, the bike seems to idle fine. After it dies I have to use the hot start every time and give it about 5 to 10 kicks to get it going, after its running it will usually die once again when I let the clutch out unless I rev it and drop it enough to brake the rear tire loose big time. In my novice oppion I think it is too rich, but even if it is I am not exactly sure how to remedy this problem.

i bought my 03 450f new and had a little problem like that at first kept stalling on me in the woods....but for me getting used to the fourstroke was the key...once u get used to it, you may never have another prob with it. if u bought it used i would check the jetting also....u never know if it was adjusted wrong from a previous owner...i have mine all stock jets and the fuel and air screw out 2 turns and i dropped the clip one position to raise the needle...i live in western pa.....and that setting seems to be the best for my bike.....but that should give u a good starting point....good luck

Thats the problem with getting a new bike. You dont know exatly whats been done to it and why the last dude wanted to sell it so bad. It has after maket exaust and thats all that I know of the mods done. Could you give me some riding tips that may avoid this problem?

Ya.. could be that you just need to get used to the clutch on that bike. These four strokes can be finiky down on the bottom. My bike doenst like the low rpm at low speed. If I dont keep the rpm up a little with good clutch control, it will stall out on me too. I had the same trouble when I first got my YZF.

Thanks for the advice, Ill try some different riding methods tomarrow. But I think I should still take it in for adjustments on monday. When you had your difficulty with stalling was it after acceleration and when pulling in the clutch like me?

It was mostly when I would slow right down almost to a stop, then try to get back on the juice suddenly. If it still acts up tomorrow, then just bring into the shop for a second opinion.

The '03 had the lightest rotating mass of all the YZ450's, and stalling was an issue. Here's some things to help.

1- Buy an extended fuel screw and learn to keep the idle mix trimmed properly. It will help with the stalling and make restarting easier.

2- Raise the idle speed a little.

3- Add a heavier flywheel. I recommend the Yamaha GYT-R racing flywheel (5oz., std on '04 models) or the Dr.D 6oz for racing. The 4oz I have is about the minimum. For offroad etc, a heavier unit like the GYT-R offroad (about 7oz) or thr Dr.D 8oz are better. These are welded in place weights, rather than bolt-ons, so it takes less added weight to accomplish the same thing. Plus, they're balanced, and they can't work loose or hide the timing marks.

Do exactly what grayracer said, I have the same bike and have an extra couple of flywheels The 6oz dr.d woks really good for almost everything. Also you said that it takes 5-10 kicks to start. if you are kicking it right then that seems too much. if you rotate it to compression and then give it full solid kick mine has always started first kick. I have found that when you have to start kicking a lot to start it, thae valves might be out of adjustment it might be a good idea to check the valve clearances.

One word - JETTING!

You're too rich on the pilot circuit. Adjust the fuel screw IN (leaner) about a half turn, and raise your idle speed. Also, blipping the throttle is a two-stroke habit that you need to unlearn. Like you said, you are needlessly adding copious amounts of fuel via the accelerator pump.

With that said, I blip the throttle some too, but if I notice I am doing it, I stop. :)

Good news. I read the replies to my post and corrected my riding methods. I raised the idle speed slightly higher than I am use to ( compared to 2 strokes). I dont have a tach, so Ill describe it this way. I adjusted it to idle at the point of going from thumping to the lowest point of running smooth and consistant ( low buzz) if that makes any sense at all. This combined with my new and improved ridding ways proved to be a great match. I rode at crooms today with my son and his ttr125, and even at his pace I only stalled the bike once. Thats not bad considering we did 6 hours of very slow trails. As far as the hard starts go, there gone, I guess if your not flooding the bike all the time it can start on the first kick! I could fell the bikes idle drop back into thump mode at idle on on the trail ride, my guess is it was just cleaning itself of excess fuel, when I let it idle longer it would go back into its fast idle.

Thanks to everyone that posted, you made my sunday a better experience.

Glad its working good for for you now!

Also I have one more new to thumpers type question. I hear a taping sound from the engine only at idle. When I give it throttle the sound goes away or is masked by the exaust. I dont know if it is normal, 2 stroke dont have all the moving parts that four strokes have. But my sons 125 dosent seem to be as loud. Everything works correctly, not overheating or causing performance problems. If everytthing is fine mechanic wise is there a particular oil that I could use that may reduce the engine noise?

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