09 WR450 Won't run properly

Hey guys. Bought a new WR450 a couple weeks ago and it just doesn't start properly if at all. It wants to die all the time if you do start it but will only start with the choke even when hot and sometimes will crank forever and not start. So i decided to pull it apart and do some investigating.

Before i go any further i do not want to hear "Take it to your dealer" simple as that.

I took care of all the basics. I check the valves, exhaust at .008 and .009 and intakes at .004 across the board, all within spec. I checked and replaced the plug, lots of spark. I did a compression test and only got 46 psi with the throttle wide open. I know of course it has auto decompression but that still seems a little low to start an engine? I did check the auto decomp and seemed to be normal. I then tore the carb apart (my do these things suck compared to my yz250!!:thumbsup: ) Check all the jets, the accelerator pump, everything is clear and is like new as it should be. Is there anything obvious i've overlooked? I can start it with an "alternate fuel source" and it then runs fine. It just doesn't want to fire which leans mean towards compression?

Any help is appreciated!

Check your carb vent hoses... maybe they are bent or clogged...

Whats the mods, elevation and jetting currently? I would pull the fuelscrew and make sure the spring, washer and o-ring come out with it and aren't stuck up in the cavity. I had an o-ring come off and get wedged up in there and led to crazy starting problems. Maybe even try replacing the pilot jet regardless if the one in it looks clean.

The vents are free, i haven't finished completely dissassembling the carb yet so i'll pay close attention to the fuel screw.

Are you running stock jetting? I never even started my '08 before dumping the stock jetting and going with the JD kit. Runs perfect and estarts every time. I've owned enough WR's to know they come very lean out of the box.

More info needed:

- is it stock?

- even the throttle stop and jetting?

If so, it needs to be 'uncorked and jetted' asap.

Read the stickies at the top of the forum.

the bike is brand spankin new, jetting stock, exhaust stock, it just came from the showroom like this basically. You wouldn't think it would come that lean from the factory that it wouldn't even start but would make sense because the plug wasn't even wet after cranking for sometime without firing.

Uncork the bike and it will run like it's suppose to.

the bike is brand spankin new, jetting stock, exhaust stock, it just came from the showroom like this basically. You wouldn't think it would come that lean from the factory that it wouldn't even start but would make sense because the plug wasn't even wet after cranking for sometime without firing.

Well there's not much to go wrong. They come jetted very lean to pass emissions but do normally start and run. Most likely you either have a clogged pilot jet or it's just too lean for your area. I see your from Saskatchewan. What's the air temperature this time of year? You may want to increase the starter jet (choke) up to a 72. Also when starting first time in the morning give it 3 or 4 twists of the throttle.

don't know if this will help but I found that in order to start mine, hot or cold, stock jetting or now with the new jetting, choke on or off, I hit the starter button ONLY. I do not twist the throttle at all and it fires right up.

First few times I gave it a little twist as I hit the button and it would not start at all.

Since u already have it apart I hope you went ahead and rejetted.

Good luck.

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