09 YZ450F Won't start - kickstart wont move!! HELP!

I just got the bike last week, changed oil/filter and air filter everything was good. Took the bike out today to a pit where the sand is pretty fine. Ran perfect all day (2-3hrs) then last ride of the day the bike just shut off. Kickstart wouldnt move, I kicked very hard and it went all the way down but sounded like a knocking the motor so i never tried again. I was driving the bike a little hard, and also jumping it. Just read then on another thread that the breather hose is in a bad place. Any suggestions on what is wrong with the bike and what steps i should take, im going out now to look at my oil filter to check for metal particles. I will probably take as much as the motor apart if i need too and hopefully not have to bring it to a mechanic. PLEASE HELP! Any suggestions ?

Anytime an engine locks you need to pull it apart and see what went wrong.

Don't try and start it again you could just end up doing a lot more damage.

yah i am not kicking it at all, just once or twice when it first happened, it the kickstart would go down but i would literally have to kick it as hard as i could so i stopped. i hauled the plug out and still the same thing, i checked the oil filter and it was full of little bits of sand, and some little tiny tiny metal shavings. so i should start taking apart the motor ?

Download the service manual from http://www.yamahaownershandbook.com.au/?r=0

When you pull the engine down make sure you label all the valve components so they can go back to the same place if they aren't damaged. If you haven't worked on engines before take lots of pictures before you pull each part.

Cam chain skipped teeth, out of time...Betcha.

take it apart. all you can do is speculate until you tear it down and have a look.

Thanks!, I'm going to tear it down tonight or tomorrow. Wishing it is nothing major!

Cam chain skipped teeth, out of time...Betcha.

Hi, a friend had this problem, the bike was rebuilt with new cam chain and tensioner and about a mile into its first ride we think its gone it again. Is it a real common thing for the 450's? And is there a cure?

Paul

No, it's just that it's almost the only thing that ever goes wrong.

If the bike was just rebuilt, my money is on the cam caps having been torqued wrong, or a bad oil pump that wasn't corrected first time through.

Hi, a friend had this problem, the bike was rebuilt with new cam chain and tensioner and about a mile into its first ride we think its gone it again. Is it a real common thing for the 450's? And is there a cure?

Exactly what GR said...No, I don't think that would be the issue with a new rebuild...It's a common problem because most people don't replace the cam chain soon enough, and it stretches easily just like a stock drive chain would...I also suspect that the cam chain tensioner has a really cheap spring inside of it, and that after a few super hot heat cycles it looses it's "springyness", kind of like what happens to clutch springs after a while (kind of bad example since they are 100 times beefier, but you get my point)...

This problem happened to me with only about 20 hours on my 07, but since the tensioner and chain have been replaced ALL has been fine (although it's been 60+ hours on it since then, so it's time to do it again)...

Alright so when I took my carb off last night and looked in at the intake valves, center and the right look fine but could be bent from what i can see, the left valve stem cracked right off with a peice of the valve sticking up next to it, i should take a picture when i go to haul the motor apart :ride:

It is possible that it was the timing chain since there is probably about 15 hrs maybe less on the bike since the last full (bottom to top rebuild),

Im hoping i just need new valves and piston.

Goose,

Where do you get your chains/tensioners and about how much?

Thanks,

Subby

Goose,

Where do you get your chains/tensioners and about how much?

Thanks,

Subby

Just replaced it with stock, and haven't had another issue with it...:ride:

Alright so when I took my carb off last night and looked in at the intake valves, center and the right look fine but could be bent from what i can see, the left valve stem cracked right off with a peice of the valve sticking up next to it, i should take a picture when i go to haul the motor apart :smirk:

It is possible that it was the timing chain since there is probably about 15 hrs maybe less on the bike since the last full (bottom to top rebuild),

Im hoping i just need new valves and piston.

Hey Bailey, just checking to see if there's any updates...

How's it going?

I've seen 2 yz's...an 06 and an 08 that the sprocket actually slipped on the cam....weird. With all timing marks lined up proper, intake cam lobes were pointing almost straight up.

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