Engine wont stay running (YZ450f)


7 replies to this topic
  • SincYZ450f

Posted April 20, 2009 - 03:00 PM

#1

I have a 2007 YZ450f. an oil seal burst and it ran without oil for about 10-15mins. Full engine strip later and everything on the inside of engine is fine/ or been replaced but it wont stay running. I stripped the top end then and found that the inlet cam was very stiff, nearly solid. The inlet cam was leaving scratch marks in the cam cap and cylinder head that the cam runs in. oil pump works fine. all oil lines seem to be clear. I can rub down the scratches but it only runs for a minute. Only damage i could find was the ball in the end of the cam cap is damaged and out of place. Any ideas why this could be happening???

  • 426 NOOB

Posted April 20, 2009 - 03:40 PM

#2

I have a 2007 YZ450f. an oil seal burst and it ran without oil for about 10-15mins. Full engine strip later and everything on the inside of engine is fine/ or been replaced but it wont stay running. I stripped the top end then and found that the inlet cam was very stiff, nearly solid. The inlet cam was leaving scratch marks in the cam cap and cylinder head that the cam runs in. oil pump works fine. all oil lines seem to be clear. I can rub down the scratches but it only runs for a minute. Only damage i could find was the ball in the end of the cam cap is damaged and out of place. Any ideas why this could be happening???


overtorqued cam caps are probably the problem here. Grayracer recommends to torque them 5 ft lbs less than the book i believe, may be a bit less. There was a thread a while back that a guy had same prob.

  • yzfmxer

Posted April 20, 2009 - 03:46 PM

#3

What is the final torque spec then. 5 ft lbs? do you have the link for the old thread?

  • grayracer513

Posted April 20, 2009 - 04:04 PM

#4

overtorqued cam caps are probably the problem here. Grayracer recommends to torque them 5 ft lbs less than the book i believe, may be a bit less. There was a thread a while back that a guy had same prob.

I think you're on the right track, but since the torque value in the book is only 7.2 ft/lb, your numbers may be off just a little :p

The book calls for 86 in/lb. and I normally use 75, which is 6.25 ft/lb, as opposed to 7.2. But torquing them incorrectly, as in out of sequence, or all in a single step are more likely to cause cap distortion than simple overtorque unless you really went crazy with it.

The trouble is now that the head needs to be repaired. Engine Dynamics can do that for you.

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  • 426 NOOB

Posted April 20, 2009 - 04:24 PM

#5

I think you're on the right track, but since the torque value in the book is only 7.2 ft/lb, your numbers may be off just a little :p

The book calls for 86 in/lb. and I normally use 75, which is 6.25 ft/lb, as opposed to 7.2. But torquing them incorrectly, as in out of sequence, or all in a single step are more likely to cause cap distortion than simple overtorque unless you really went crazy with it.

The trouble is now that the head needs to be repaired. Engine Dynamics can do that for you.


whoops in. lbs is the mistake I made. haha

  • Fever26

Posted April 20, 2009 - 05:41 PM

#6

Actually, Outside of anything else.. Be sure you check you cam timing after an issue like that. If the cam seizes the engine still wants to go therefore it can turn the gear on the cam. They are a pressed fit on a yamaha. Rarely will ever turn under notmal conditions but in yoru case may have... Doubel check before you get more damage. Like a valve stuck in a piston..Ouch.

  • SincYZ450f

Posted April 21, 2009 - 10:39 AM

#7

thanks for all that i will try it. any ideas if the damaged ball in the end of the cap would make a difference?? Any 1 have the link to other thread like this?

  • grayracer513

Posted April 21, 2009 - 02:08 PM

#8

thanks for all that i will try it. any ideas if the damaged ball in the end of the cap would make a difference??

If you mean the ball that plugs the end of the oil drillway, I see virtually no way damage it except by beating on it with a hammer, and as long as it doesn't leak oil out of the passage around the ball, it doesn't really matter anyway.





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