2009 yz450 blew up, what piston and cams?


3 replies to this topic
  • YzFromHell

Posted April 16, 2013 - 10:37 PM

#1

I blew the motor up on my completely stock 2009 yz450f, this was surprising because i only have 38 hours on the motor and i religously change the oil and oil filter every 5 hours with a new air filter every ride... not typical of a yamaha at all! however i do find i am riding it on the edge majority of the time while riding tracks, and have gotten it very hot in some sand hill climbs where it is very highload/low air flow through the radiator situations.

so i am going to completely rebuild it, however,
I am not sure what cam and piston combination would be best?

I already bought a pro circuit ti-4r exhaust system, i know the stock exhaust is aweful, I found myself needing the clutch out of corners way to much because of the lack of bottom end the bike has stock.
I also got an 06 cdi for it to help with this bottom end situation as well.

Now for the motor rebuild, im going to have the head mildly ported and i am wondering what cam and piston combo will best compliment the system. Obviously valve seals and cam chain will be replaced.

I am going to get a cosworth piston, either a 13.75:1 or 13:1 compression ratio, Im leaning towards the 13.75:1 piston, as im sure it will be fine with 91 or 94 pump fuel as i ride between 2000-3000ft.

What my main question is, what cams would be best suited for the motor build?
Should i go with hotcams stage 2 or gytr cams? From what i understand they dont need upgraded valve springs?
This is why webcams are out of the question.

I have read that stage 2 hotcams have negligible bottom end losses with gains through the mid-top end.
GYTR advertises their cams have the same affects, although i have never heard anything about them in this engine.

All information will be appreciated and valued,
Thanks, YZFH

  • Gunner354

Posted April 19, 2013 - 05:45 PM

#2

I blew the motor up on my completely stock 2009 yz450f, this was surprising because i only have 38 hours on the motor and i religously change the oil and oil filter every 5 hours with a new air filter every ride... not typical of a yamaha at all! however i do find i am riding it on the edge majority of the time while riding tracks, and have gotten it very hot in some sand hill climbs where it is very highload/low air flow through the radiator situations.

so i am going to completely rebuild it, however,
I am not sure what cam and piston combination would be best?

I already bought a pro circuit ti-4r exhaust system, i know the stock exhaust is aweful, I found myself needing the clutch out of corners way to much because of the lack of bottom end the bike has stock.
I also got an 06 cdi for it to help with this bottom end situation as well.

Now for the motor rebuild, im going to have the head mildly ported and i am wondering what cam and piston combo will best compliment the system. Obviously valve seals and cam chain will be replaced.

I am going to get a cosworth piston, either a 13.75:1 or 13:1 compression ratio, Im leaning towards the 13.75:1 piston, as im sure it will be fine with 91 or 94 pump fuel as i ride between 2000-3000ft.

What my main question is, what cams would be best suited for the motor build?
Should i go with hotcams stage 2 or gytr cams? From what i understand they dont need upgraded valve springs?
This is why webcams are out of the question.

I have read that stage 2 hotcams have negligible bottom end losses with gains through the mid-top end.
GYTR advertises their cams have the same affects, although i have never heard anything about them in this engine.

All information will be appreciated and valued,
Thanks, YZFH

Two questions? What actually "blew up" and what kind of oil do you use?

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  • MaxPower

Posted April 20, 2013 - 10:01 PM

#3

I can't say what cams are best
But I can guess your 450 engine failure came from sand being sucked into the engine vent. Unless it is rooted into the air box on the 09. Then I haven't aa clue.
Good luck. I will be interested in hearing what cams are best also

  • YzFromHell

Posted May 01, 2013 - 08:58 PM

#4

Two questions? What actually "blew up" and what kind of oil do you use?


The exhaust cam is siezed into the head and the piston is siezed as well.
This was from oil starvation because the valve seals were leaking and it was burning oil, i tried to stay on top of it until i could have the head apart but one hot day it burnt a lot and it bit me in the ass. i use castrol motorcycle oil, i believe it is 10w-40

I can't say what cams are best
But I can guess your 450 engine failure came from sand being sucked into the engine vent. Unless it is rooted into the air box on the 09. Then I haven't aa clue.
Good luck. I will be interested in hearing what cams are best also


I do ride in the sand a ton, so that could be a likely cause of why the valve seals started leaking.. leading to the engine failure.
unless i can find a set of gytr cams for close to the same price of the hotcams, the hotcams it will be.





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