2007 YZ450F first start

I just bought a 2007 450, everything is still stock; pipe, jetting, and I always have a hard time getting it to start the first time when I go out. After it gets a little warm, fires up pretty much first kick every time. Other than trying to kick my brains out, or ultimately tow it, any ideas?

On the first cold start, it helps to give the throttle a couple of 3/4 twists to prime the engine with fuel from the accelerator pump. Then, open the choke and kick the bike with the throttle either completely closed, or just barely off idle. It should start fairly easily. The one thing you have to get over, if you do it, is the two-stroker's rather unexplainable habit of rolling the throttle open as your foot goes down on the crank. You'll never get it going like that.

Mine was a little hard to start too, and still is when it is cold in the A.M. I found giving the "smallest" shot of gas when you know the kick is in TDC really helps it come to life.

The newer YZF's don't seem to be as prone to start up flooding, but that is just my impression. If that does not help, make sure to get that fuel screw dialed in when you do have it running, and you might try a fresh plug just to take that out of the equation.

Rejet the bike. It's too cold out in the AM right now and your not giving it enough fuel. Put a 45 pilot and a 168 or 170 main in, and it should kick over within 3-4 kicks.

The pilot is the jet that will help with the starting, but you should change them both while your in there.

With the proper jetting, you might not even need the choke, hope this helps.

The '07 comes with a 45 pilot already. Depending on altitude, that should be enough. But it does follow that the colder it is, the more fuel you'll need. That's why the priming is important.

I have an 06 YZ450 and it does the same thing. Once its warm it start first kick almost always :ride: ....and I keep wondering why the supercross anouncer guy keeps saying that its sooooo hard to start a warm four stroke? Is it just all other non Yamahas :ride:

When I start my cold 07 450, I blip the throttle twice, kick it slowly twice to prime it, then kick firm and all the way through with NO throttle. Easiest starting 4 stroke I've ever owned, cold or hot. The 48 pilot should help.

after break in you will find the motor will free up more, and it will get easier to start, (kick over)

Just got mine yesterday brand new 07'. Kicked on it for 30 mins or so and couldnt get it started. I was freaking out!!! My buddy has the 06 250f kicked it one time got it to fire then it died. The dealer had the fuel screw way off. We adjusted it and the 450 roared! Now i gotta get some good weather to ride the thing!

I tried a #48 pilot in my 07 (SoCal area). Made it harder to start. Went back to the 45, put the fuel screw out into the 2.25 - 2.5 range, and is starting easier and running cleaner (less hot stalling too). Last thing was to put the idle up to 2100 or more (to reduce stalling). This is what MXA did and most of the locals are running successfully.

I tried a #48 pilot in my 07 (SoCal area). Made it harder to start. Went back to the 45, put the fuel screw out into the 2.25 - 2.5 range (even though this was much farther out than standard fuel screw setting would result in), and is starting easier and running cleaner (less hot stalling too).

Last thing was to put the idle up to 2100 or more (to reduce stalling). This is what MXA did and most of the locals are running successfully.

I ...put the fuel screw out into the 2.25 - 2.5 range (even though this was much farther out than standard fuel screw setting would result in)...
The manual calls out 2 1/8 as nominal.

I never had a starting issue with my 07 until recently. Changed my oil, put a new scotts filter in it, put a twinair filter in it and it just didn't want to kick over. Took me about 10 min to get it goin.

Not sure if it was the twinair, maybe I over lubed the filter? Went out today and had no issues starts on the 2 or 3rd kick. Anyone have a similar experience? If I have trouble again I will use the advice given.

I am betting that the Twin air filter would make a difference expecially with a different configuration and you having liberally oiled it.

I always have trouble if I try to start it just after cleaning and oiling the air filter.

Next day I find there are no issues at all.. Once it had time to settle down maybe dry out a bit..:censored:

Thanks for the advise....... went out this past weekend, 3rd kick and it fired right up.

My 2007 450 is poping when i roll the throtle back off.

I am at 46k high in Colorado.

Want to try race fuel to jet it in.

bought an aftermarket adjustment screw will try today in practice.

Also need to raise throtle a little so it will not die in the holeshot corner.

Sound good to you guys.

Greg

My 2007 450 is poping when i roll the throtle back off.

I am at 46k high in Colorado.

Want to try race fuel to jet it in.

bought an aftermarket adjustment screw will try today in practice.

Also need to raise throtle a little so it will not die in the holeshot corner.

Sound good to you guys.

Greg

go up to 48 pilot jet and MJ 1 size, if you have stock 165 in go 170.

i did and poping was elimated.

Practice today and bike ran great.

Maybe it was too cold when i was warming it up last night to get ready to race this week end.

Raised throtle a little and does not die any more.

It is only one week old and raced once last sunday.

They did tell me where i bought it that carb. was set up.

Greg

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