Kick start locked up! Need some help!

Hello all! New to the forum.

Soooo i bought a 2013 yz450f with 6 hours on it. It probably has around 16-20 hours on it now.

I was riding at the dunes on Saturday, bike was running great, shut it off to BS my friends. When i went to kick it back over, the kicker made an awful clanky sound then locked. We could shake the tire in gear and free it, then it would do the same thing with the awful noise and lock again. We loaded it up and took it back to camp.

My buddy pulled the tire again with it in gear backward and it made another awful grinding noise, then kicked fine with no noise but would not fire.

When i got home. I found the bike was way out of time. One tooth on the exhaust and several on the intake. Also, the intake cam shaft would not move after i removed the tensioner, but i freed it with my hand and it moves easy now. After re setting the time, the bike runs fine (in my garage anyway), although it did take awhile to kick over the first time.

I suppose my question is, why did it do this and is anything else damaged? Do i need new chain, guides, tensioner, or what? Could there be damage to my piston? I dont visually see any damage to the chain or sprockets on the cam shafts. Im no mechanic, but id prefer to keep it in my hands if possible. Let me know what you guys think! Thank you.

Anyone anyone???

Sounds like the cam sprockets may have slipped, or the chain just jumped time. I don't see how the chain could have jump with such low hours though. There could be damage to the piston/valves if they made contact. Your best bet is to pull it apart and check. Can you take a photo of how the cams are oriented at TDC, that might tell us if the sprockets slipped at all. Grayracer will poke in here at some point probably tomorrow, not sure if he would be on today since it's the holiday, but he's the resident genius on the bikes. I will try to help with what I can until he comes around.

They cam lobes are oriented where they should be at tdc according to the manual, just by visual comparison. They may have slipped though.

Does it seem like it's running ok now that the timing is back where it should be? No funny noises or anything?

It seems ok, but this is just idling in my garage with a few revs. I cant really ride it here. It is very difficult to start. Tried to start it today and gave up. Something is still wrong. A lot of kick back, its never been like that before.

I would definitely pull it apart and inspect for damage. My guess is the piston made contact with the valves. Which will most likely require a full top end rebuild.

Thats what im afraid of. What about the fact that it did fire and run fine on the stand? And why would this happen in the first place? Very frustrating:/

That I can't answer. Maybe extra wear on the cam chain, for whatever reason cause the timing to jump. With that low of hours I really don't know.

How long did you have it running in the garage? Long enough to get warmed up?

Since you already had it down to the valve cover being off, it doesn't take much more to pull the head off and inspect it. All you need is a new gasket, that way you can answer the question once and for all instead of it being in the back of you mind all the time.

Edited by 0bigsilver6

Ya i suppose ill pull it off and let you know. Ive never gone that deep into the engine before but no time like the present! One other thing while i got your attention, i cant seem the pull that fly wheel cover off. It seems to be stuck on a spring or something. Am i missing something?

And ya the bike warmed up.

The stator is mounted in the cover, so when you are pulling it off, you are pulling the stator out of the flywheel rotor, which attempts to hold it magnetically, and also requires that you pull the cover fairly straight off. 


It sounds like your intake cam seized, but it may not have.  look for scoring in the bearing surfaces in the head and cam caps.  Check the chain carefully for any stiff links.  In fact, replace it even if you can't find one.

Thanks gray, do you have any input on why this might have happened on a bike with such low hours? Do u think the valves may have slapped the piston? Im just confused on why it seems to run good, but so impossible to start.

I know i can answer all my questions if i pull it apart, but i dont have time right now, and ill lose sleep over it all week.

20 hours in 3 years isn't a lot of time, which means the bike may have sat for long periods.  In the majority of cases I've worked on where the timing has slipped, extended periods of non-use have been a common thread.  If the bike was using an oil that isn't particularly good at corrosion prevention, and some otherwise good oils aren't, especially if they were put away on oil that needed changing, rust could be involved.  One stiff link in the wrong place at the wrong time, the engine kicks back or bounces off compression too much, and that stiff link can fool the chain tensioner, causing a skip/


If the bike runs, you certainly will not have bent the valves very much, if at all.  Solvent check them, or run a leak down test.

Thanks gray. That would make sense. I changed the oil as soon as a bought it, i wouldnt be suprised if that wasnt the first oil change its had, it was dirty.

Would you recommend a new tensioner?

Yes. Probably not faulty, but....

Well thanks gray and silver for your input. Ill do some more poking around. If the valves and piston check out, ill replace the chain & tensioner and hopefully she fires right up.

Edited by RDub12

ImageUploadedByThumper Talk1464748677.310186.jpg

I got to looking at my flywheel and see there are two marks. One wide mark (left) and one dash(right). Originally i used the dash (shown to the right) for tdc, maybe this was the cause to my starting problems? Which is the correct mark for tdc? Ive searched this topic but couldn't find anything with marks similar to mine.

Also, how do you test valves with solvent?

Thanks guys.

I don't know if yours is the same as mine, but if I recall right, there is a T that means TDC, and then a line right after that, that indicates the spark plug firing point.

I can't see the marks on your picture, so I'm not sure if it is the same.

To figure out which mark is TDC for sure, stick a screwdriver down the spark plug socket and turn the engine until it reaches its highest point, then see what mark lines up with the line on the case. That's one way to be positive about it. Assuming the flywheel is keyed properly.

To test the valves, you have to pull the head off, pour a solvent, alcohol or MEK are some examples on top of the valves, then pick up the head level so the solvent doesn't pour out, and watch to see if it's seeping past the valves.

Edited by 0bigsilver6

You can have a shop do a leak down test to show whether the valves and rings are sealing or not without removing anything but the spark plug. 

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now