07 YZ450F Cam chain


41 replies to this topic
  • accelorator2000

Posted April 17, 2007 - 10:03 PM

#1

Has anyone else had any trouble with the cam chain on their 07 yz?
my friend and I have both had the same problem. The cam chain has
gotten so loose that it skips over the cams and the bike ends up
being so out of time that it won't run. We are in the process of
dealing with Yamaha to remedy this. If anyone else has experienced
this problem, it might be a recall issue.

  • grayracer513

Posted April 18, 2007 - 08:09 AM

#2

First I've heard of it. Sounds like a tensioner problem, but the YZF tensioners are almost too simple not to work, and haven't been a problem up to now.

  • 642MX

Posted April 18, 2007 - 09:29 AM

#3

How many hours are on the bikes?

  • accelorator2000

Posted April 18, 2007 - 04:48 PM

#4

My bike has about 20 hours on it, and my friend only has about 10 on his.
Both bikes are in the shop now, and apparently these are not isolated
occurances. The Yamaha rep is coming to check things out next week.
I think they may end up doing a recall, because the cam chain failed on both
bikes. It stretched an unusual amount.

  • Captaincautious7

Posted April 18, 2007 - 05:02 PM

#5

Keep us posted. Were there any symptons before this? It's my first Yamaha and I have about 25hrs but am still getting familar with standard engine noises or what I assume would be standard noises.

  • blueballz006

Posted April 18, 2007 - 10:48 PM

#6

The same thing happened to my 06 yz450. (At about 50-60 hours) It skipped over the teeth of the cam gears one day and stalled out. The thing is though, the chain wasn't stretched and it wasn't the tensioner. The chain itself becomes warped and stiff. This is probably due to overheating the bike at one point. I figured that the cam or crank gears would be damaged too. But, I took it all apart and inspected everything. The only bad part was the cam chain itself. I put a new $15 chain on, slapped it back together and I've ridden it about 30 trouble free hours since then. You can check your valve clearance while you've got it all apart too. Also, my worst fear when I found out my timing had jumped was that I may have had valve to piston contact. But, It was all good.

  • Ga450owner

Posted April 19, 2007 - 05:40 AM

#7

First I have heard of it too....but it makes you wonder if the cam chain is made from the same folks with the same quality as the stock drive chain......this could be very very bad.

please keep us posted on what Yamaha has to say and do about it.

  • Budlite

Posted April 19, 2007 - 06:32 AM

#8

It did it to my 06 as well. Backfired sitting still in the driveway and jumped time. The piston did hit the valves and pushed them up into the cam. It ruined the intake cam not the valves, glad the cams are hollow ! Slight hone job on the bearing surfaces on the intake cam and a new Hot Cam and she purrs like a kitten and rips on the track. Luck was on my side this time.

  • txknucklehed

Posted September 21, 2009 - 10:34 AM

#9

when your 06 jumped time did the kicker not move? mine wont kick. it stalled and started briefly then seemed to lock and i cant kick it now.

  • Civilguy

Posted September 21, 2009 - 12:27 PM

#10

if your engine is locked up you may have bent a valve. the only other way it could be locked is if the chain is kinked so bad it is jammed at one of the sprockets in the head or around the crank.

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  • lftdjeep426

Posted September 21, 2009 - 12:28 PM

#11

when your 06 jumped time did the kicker not move? mine wont kick. it stalled and started briefly then seemed to lock and i cant kick it now.


Sounds to me like you dropped a valve. which means that the valve is bent and probably keeping the piston from moving (possibly).

I have had my fair share of gremlins on my 07' 450..... I've got about 53 hours on it and have been into the motor 3 times now. diagnosis the first time, new piston the second time (just because I had it apart at 48 hours) then dropped both exhaust valves 6 hours later. Just put the first 8 hours on it last wed and this weekend and its fine so far..... Noisy as always.....

  • bakeyz426f

Posted September 21, 2009 - 12:29 PM

#12

you may have broke a valve. it happened on my 2002 yz426f when timming skipped. it made a quick noise and stalled. kick starter wouldnt budge. ruined the head so now i need another bike.

  • txknucklehed

Posted September 22, 2009 - 07:28 AM

#13

mine stalled after a high speed pass, right as i was whipping it around to make another pass. it just sputtered and died. i tried to kick it and it wouldn't catch. it was about 100 outside so i figured it might be hot. i walked it for about 5 minutes let her cool down a touch and she fired for a second stalled when i blipped the throttle. it felt like it wasn't decompressing when i tried to kick it the next time, so i walked it for a minute to let it bleed down. it kicked after about 5 more minutes, but would not start. so i walked it the 3 miles back to the truck and loaded it and went home. the kicker is still locked????? what happened? what should i look for to diagnose the problem? any help or suggestions would be greatly appreciated. Anybody on here From Austin tx. and looking to make a couple extra bucks? i could use your help. thanks

  • lftdjeep426

Posted September 23, 2009 - 04:30 AM

#14

mine stalled after a high speed pass, right as i was whipping it around to make another pass. it just sputtered and died. i tried to kick it and it wouldn't catch. it was about 100 outside so i figured it might be hot. i walked it for about 5 minutes let her cool down a touch and she fired for a second stalled when i blipped the throttle. it felt like it wasn't decompressing when i tried to kick it the next time, so i walked it for a minute to let it bleed down. it kicked after about 5 more minutes, but would not start. so i walked it the 3 miles back to the truck and loaded it and went home. the kicker is still locked????? what happened? what should i look for to diagnose the problem? any help or suggestions would be greatly appreciated. Anybody on here From Austin tx. and looking to make a couple extra bucks? i could use your help. thanks



Really easy! Again, my bet is that you have/had a valve sticking in the guide. Judging by you saying that it quit (valve stuck) and there not being any compression when kicking it (valve stuck open) and then it cooling (metal contracting) and firing back up until it got warm rapidly (valve stuck again). My guess is that the valve might be stuck all the way open and is jamming against the piston, which is why its not moving.

Just remove the tank and top engine brace to get the valve cover off. Don't worry, if you have never taken it off there is nothing that is going to jump out at you. once you have the valve cover off visually inspect the cams and also the buckets (which ride on top of the valve springs). These are the nickle size flat areas underneath the cam lobes. If everything looks ok, unscrew the small and large plugs on the left side of the engine case (use the biggest flathead screw driver because these plugs are plastic and will damage easily). Once you have those removed use a 17mm socket on the crank (inside of the larger hole) to turn the engine counter clockwise at the same time look through the top hole and as you turn you will see and "H" and then about a 1/2" past that you will see an "I". You want to line that "I" up with the index mark on the side of the case directly above it. This lets you know that the engine is in top dead center position. Now you need some feeler/gap gauges (if you don't have any you can buy them at any auto-parts store. And do yourself a favor and spend the extra $2.00 and buy the longer ones. It makes everything much easier.) now take those new feeler gauges and you are going to find the correct gap spec and slide it in between the cam shaft and the nickle size bucket. If it is excessive gap (a huge amount) you know that a valve isn't fully closed. I can't remember off the top of my head the gap clearances (.004 to .006 for exhaust and .002 and .004 intake?) someone correct me.

This will give you an idea if you dropped a vlave without pulling the head. Now if the engine won't turn with the 17mm socket on the crank you know you have a major failure. Then its time to remove the head and cylinder and start diagnosing the problem.

If you have a decent set of "meachanical skills" I encourage you to tear into the engine yourself. If you have the motor manual it is relatively simple as long as you pay attention to the instructions and layout your bolts. This can also save you a ton of money in the shop if you have to do a head job and just take them the head instead of the whole bike.

For instance, I just had to do valves on mine and the difference was $575 in labor if I took them the bike compared to $200 by taking them the head by itself.

I hope this helps, just my $.02. :busted:

Good luck, I was just in your position and since the rebuild I'm 10.5 hours on the motor with no problems! :thumbsup:

  • txknucklehed

Posted September 23, 2009 - 09:32 AM

#15

it had compression.it felt like it wasn't automatically DEcompressing. thanks for the tips i will try it.

  • Aka.Goose

Posted September 23, 2009 - 01:02 PM

#16

I think it's simply your cam chain tensioner is failing and allowing the chain to skip a tooth causing it to go out of time and give the feeling of the kickstart locking up...Just replace your cam chain tensioner and cam chain, you should be good to go...
I don't think it's an issue with the valves...

  • txknucklehed

Posted September 23, 2009 - 04:17 PM

#17

thats what i am hoping!!!! i have had a few people tell me that is probably what is happening. from what i understand the tensioner works off oil pressure. i had just come off wide open throttle so i think that might be why it skipped! sudden oil pressure drop and she skipped. i had been WOT for at least 2 miles i love the wide open spaces here in texas. just twist tickle the shifter and hang the **** on.!!

  • Aka.Goose

Posted September 23, 2009 - 05:12 PM

#18

from what i understand the tensioner works off oil pressure.

I don't know anything about that, it's just a spring inside the tensioner unit...My guess is that this spring is cheap, and begins to loose it's springyness after several extreme heat cycles...
Just check to make sure your valve clearances are in spec, maybe pull the whole head off and check to make sure the piston rings are good, and that you aren't getting any piston slap on the head or valves...
Definitely a place to start, it's happened to me, and a few others here on TT...

  • grayracer513

Posted September 23, 2009 - 07:25 PM

#19

The tensioner is a beautifully simple device, and is nearly foolproof. A spring tightens an internal screw a little bit more whenever any slack appears, and no amount of force can push it back out, short of physically breaking it.

The problem on the later bikes is almost always the chain:

http://www.thumperta...972#post8615972

  • txknucklehed

Posted September 26, 2009 - 03:45 PM

#20

so i pulled the valve cover off this morning. lined up TDC and it looks like everything is lined up correctly, i counted 14 links between the indexing marks. when i rotated the motor counter-clockwise, it seemed to slip around smoothly and then it would almost grind through about 20 degrees of the rotation then smooth out again. the chain felt tight but not overly tight. i have a sinking feeling that i may have cooked the main bearing or the crank bearing. would there be any tell tale signs ? short of cracking the cases? i just bought this bike from a second owner. he claimed he put 6 hours on it, and he said the first owner only put 6 on it. i call BS who really knows. any suggestions?





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