06YZ450F Bogging

Hey everyone,

I bought a 06YZ450F this past May and have loved it. 2 weeks after I purchaed it, once I broke it in, I had the shop rejet it (it was backfiring a lot). Since then, it ran great.

Two weeks ago, it started bogging at the first throttle crack. If I roll it on slowly it is ok, but if I turn it with any speed it bogs and/or dies. I thought I might have over oiled my air filter (but I have changed it twice since). Prior to 2 weeks ago, the same crack would not bog it. I have not changed settings or parts since then.

Any suggestions on where to look? I assume it is a jetting issue. What might cause it to change all of a sudden?

1) The bike is stock, with only a Boyseen water pump put on in June.

2) I ride MX and Enduro in Central/South Texas

3) It is hot and humid, but it is always that way down here:)



Your fuel mixture screw didn't fall out did it?

I couldn't imagine, but I am certainly going to check when I get home.



Your fuel mixture screw didn't fall out did it?

I was thinking the same thing.. If it isn't out, then it is probably close to falling out. You should replace it with a zip tie screw if you have the stock one in. Otherwise turn the screw in, then back it out about 2 turns and adjust from there.

maybe, dirty air filter??? just a shot in the dark..

the temp and humidity levels haven't changed have they? my bike ran great all spring then about halfway through the summer the thing bogs like crazy. a smaller pilot jet and one smaller on the main was the cure, we have been in a heat wave lately so temps are hotter and humidities are higher than normal, you might be able to dial it out with the pilot screw though. try a 165 main and a 45 pilot if thats not what you are already running.

Sounds like they jetted the pilot too rich.

Sounds like they jetted the pilot too rich.

I am thinking the same thing. If your bike doesn't pop at all, even a little bit, on decel it might be to rich. I would try turning your fuel screw in a 1/4 turn at a time and see if that helps. If it doesn't and if they put in a 48 or bigger pilot you might try a 45. Mine did the same thing in the woods and I adjusted the fuel screw and that cleared it up but it now pops very slightly on decel. If you are still running a stock fuel screw you also might want to get a Zipty or Stealth it will help with the fine tunning.

If you've lost the fuel screw get the Zip-Ty with the knob on it, they make two versions. You'll also need the spring, washer and o-ring. Suzuki sells them individually. Honda, Yamaha, and Kaw sell them as a set. Big difference in price because they come with the screw itself. You might consider extras as they are hard to get in a hurry. Once installed, safety wire it so that if it comes loose again, it won't fall completely out.

Our fuel screw fell out and we had this problem, so we bought an aftermarket one and turned it in all the way then 1 1/4 out and it runs great. I just have no clue how the stock one could fall out but w/e.

Ok, I checked it. It has not fallen out. Unfortunately, I was not smart enough to ask the dealer where they set it when it was rejetted...so I don't know if it has come loose at all.

I figure I will reset it to 1.5 to 2 turns out and go from there.

Thanks for the help everyone!

Yea, I thought it might be that or that I over oiled the filter. So I have changed it twice over the past 10 days just to be sure.

How many degrees will make a difference? I live in central texas, so it is HOT. But I had it jetted in late may or early june. So it is only a few degrees hotter now than early summer.

Yea, it does not pop at all. Boy when it was new, before the rejet...it poped like a popcorn maker. But even now that it is bogging, no pops.

i will try turning in the screw to see how that helps.



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