stupid 06 wont start

Ok guys, I have an 06 YZ450 that is freaking impossible to start. To get it started I have to hold the throttle open slightly and kick for ever, it will also back fire several times when I kick it. I cant believe how hard this thing is to start. heres the mods, ported head, wb carbon pro, tokyo mods box(set on 2). I have checked engine timing its correct, I checked all the jetting but im not very good with jetting.

NFPR needle 5th clip(counting down from top of needle)

172 main

45 pilot

air screw 2 turns.

I am looking for help im tired of kicking. also once its hot you might as well push it off the track its not going to start again.

all help is greatly appreciated.

When's the last time you've had the valves adjusted?

havent checked those yet, i was hoping it would be jetting.

IMO, more than 80% of starting problems originate with an improperly tuned idle circuit. This is especially true when a lot of the tuning that's been done has focused on either eliminated any trace of decel backfire, or getting the bike to tolerate ridiculously quick jabs at the throttle from very low RPM.

But the other suspect here is your CDI. Try the stock one back on it.

IMO, more than 80% of starting problems originate with an improperly tuned idle circuit. This is especially true when a lot of the tuning that's been done has focused on either eliminated any trace of decel backfire, or getting the bike to tolerate ridiculously quick jabs at the throttle from very low RPM.

But the other suspect here is your CDI. Try the stock one back on it.

I unfortunetly do not have it. It didnt come with the bike. Where would you go on jetting?

Does it idle well when it is running? Find it odd that it is not starting until you open the throttle a little - secret with 4T usually is to kick with no throttle at all except a few pumps prior to cold starting.

If you do the what is suggested on the thread that gray has posted above, and don't get any significant change or have to change anything, it may be worth altering the idle setting, making it idle slightly faster might just do the trick to make it start easier.

Tuned bikes can be a pig sometimes though - how many pro's can't start their bikes when warm?!

At least check the valves.. It isn't difficult or time consuming

Ok checked and corrected the valves tonight, the intake valves were way off. the far left valve i was able to pass a .254mm through it. Was way off also. corrected all the clearances, ill see if it starts tomorrow night when i get home.

Ok checked and corrected the valves tonight, the intake valves were way off. the far left valve i was able to pass a .254mm through it. Was way off also. corrected all the clearances, ill see if it starts tomorrow night when i get home.

That's a pretty big gap. What has changed since the last valve inspection? When was the last time that it ran properly? If I had a gap like that out of the blue I would look for one of two things: 1) valve stuck open on carbon or 2) bent valve not closing. Maybe a broken valve spring, too, just because.

im starting to lean towards a valve sticking open, timing is all correct, and ignition seems to spark properly. I guess this weekend im going to pull the head and see whats up. All I can get it to do now is back fire when I try to start it, I used to be able to get it to start but now all it will do is back fire, anyone else got anymore suggestions?

Does it backfire through the intake or the exhaust? I know that I had an exhaust valve stick open and it would backfire through the exhaust whereas intakes spit back into the carb. The backfire that I dealt with was built up fuel trying to push the piston down, but would spit fire through the stuck valve. So, if you are getting backfiring through the carb, then it is the stuck intake valve. As a guess. You could try lightly tapping the head of the valve (with cams and bucket removed) and then look down the intake tract to see if the valve moved at all.

Well I believe I have tracked down the problem. I decided to look deeper into the electrical system, I pulled the stator cover and checked out the maneto, it appeared as if something had been rubbing on it. I checked out the flywheel and found 2 holes punched in the flywheel, pretty sure I've located my problem.

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