07 yz450 cam slip


8 replies to this topic
  • cablemonkey334

Posted March 14, 2008 - 05:39 AM

#1

i have a 07 yz450f just shimmed the thing an rode it for 2 hours an it ran fine. got it out the next day an started it , rode about 100 ft. an it died . l kicked it about 100 time ,drug it with a truck no luck. went home an check the timing an it was way off. so ,we retimed the bike an rode it but it seems down on power an back fires and is hard to start. if you look at the cams the intake cam has more angle on it than the exhaust . i m 100 percent sure that the motor is set to tdc an i m on the rite timing marks. only thing i can think of is the intake cam slipped . anyone ???????

  • kyle450rider

Posted March 14, 2008 - 05:49 AM

#2

DOes not sound like it. Your cams should be facing AWAY from each other if I remember right. Send a PM to Grey, he is the yamaha master on this site.

  • Speedracer747-400

Posted March 14, 2008 - 06:50 AM

#3

How did you verify the engine is at TDC? Did you use the marking on the flywheel or insert something in the spark plug hole to physically verify? Check the key that aligns the flywheel on the crankshaft to make sure it didn't shear. If that checks ok it's possible one of your cam gears has slipped on the cam shaft.

  • grayracer513

Posted March 14, 2008 - 07:45 AM

#4

The cams can and occasionally do slip in their sprockets. Look at the illustration on page 4-25. This gives you a look at what the relative lobe position should be with the timing marks on the cams in the TDC position. The intake should be a mirror image (more or less) of the exhaust, facing up and back just as the exhaust faces up and forward.

If the cam has slipped, You could have it fixed, but that would require a specialty shop familiar with the the YZF head, and the precise cam/sprocket timing.

One of the causes is that the intake cam may seize to the head briefly (the clearances are very small), so carefully check the bearing saddles and caps for damage.

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  • thumpyz

Posted March 14, 2008 - 10:43 AM

#5

So when you discovered the timing was way off, was it the cam gear that was off, or the lobe symmetry? If it was timed wrong on accident you might have damaged your valves, i am not sure if being out of time like that would cause a cam gear to spin. good luck.

  • grayracer513

Posted March 14, 2008 - 12:22 PM

#6

Under most circumstances, the intake cam can be very retarded, as it would be if the sprocket slipped, without having valves run afoul of the piston.

  • jwidd

Posted March 14, 2008 - 07:14 PM

#7

I have a 2006 YZ450 and I had the timing chain slip two teeth on the exhaust side. I pulled the chain and it was stiff and kinked. It had streched to the point the links were rubbing on the bushings.

I replaced the chain, it fired right up and things have been just fine since. For about fourteen bucks, I would change it.

  • cablemonkey334

Posted March 23, 2008 - 05:55 PM

#8

replaced both stock cams with hot cams stage 1 an the bike started on the first kick an runs great , the intake cam did slip some how , no clue but it did. the hotcams gave the bike some good bottom end.

  • gdbarr1976

Posted March 24, 2008 - 08:36 AM

#9

I just did a top end rebuild on my 06 yz. When I started it the cams seized and the timing slipped. I had torqed the cam bolts to 7.2ft lbs per the manual and used assembly lube. What did I do wrong?

I cleaned up the races or whatever you call them and the cams turn freely now. Any suggestions?





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