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Old 11-15-2006, 07:00 PM   #1 (permalink)
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This is a simple write up for any year yamaha yfz450 quad to convert to yz450f cam timing.... also known as the "cam mod". No this will not hurt nor damage the motor in any way IF done correctly.

I know some people have heard that there could be some issues with doing the cam mod on an '06/'07 yfz450 so I have put this together to help some folks out. The cam timing is the same for all years yfz450. Yamaha has not made any changes from year to year.

Please wash your quad well. You do not want dirt or debris to fall into your newly exposed engine. That would take a fairly simple (with the right tools) job, and turn it into a nightmare!!

Remove your tank plastic/ and side panels.

Remove the gas tank.

Dissconnect the vent hoses/ air boot to carb boot/ spark plug/ carb. There is no need to remove your carb all the way just tie it out of the way.

Remove the top valve cover from motor.

I place all parts exactly how they came off into a clean box.

Remove the side cover plugs, and use a 17mm socket, and counter clockwise, rotate the crank to TDC on the combustion stroke. The combustion stroke is right after you see the intake valves move.... not the exhaust valves!! The cam lobes will be up and away from each other at a 45*.
Line up the mark in the top window with the center of the hole. You will see a I-I and then a I. Line it up with the last "I" as the first two is actually the range that the spark plug fires in. Here is a picture:


Thanks NHYFZ450

Now you need the factory service/ repair manual!!

Release the tension on the chain from inside the ACCT.You have to remove one bolt and copper washer, and then you can stick a small flat blade screw driver into the ACCT and turn it until it "clicks" in place. It is spring loaded so be carefull. By doing that this will retract the tension from the chain.


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Remove the bolts that hold down the cam towers. Do this is 1/4" turns evenly across all the bolts in a criss cross pattern. This way it keeps the towers from warping as you remove them.


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Be very carefull to not drop the 2 half moon clips down the motor. There is one for each cam.


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Here is the underside of the cam tower.


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I always place CLEAN rags into areas of the motor that is exposed that I do not need open. Take note of which side of the half moon clips faces the sprocket side and which faces the lobe side. There are two bolts that are longer then the rest. Do not mix them up!!
Mark the cams (both) with a marker or white out on the sprocket and the chain. This way you can see where you started at, and where you ended up at. Here is a marked stock yfz timed cam gears.


Thanks YFZ450Alterego

I had to remove both cams to be able to rotate just the exhaust cam. Some may not need to. It depends on how stretched your cam chain is.
I lay a long screw driver across the top of the head under tha cam chain in case I loose my grip on it so it doesn't fall into the exposed opening of the head.
Rotate your exhaust cam 1 tooth clockwise. Then replace the intake cam if you had to remove it to rotate the exhaust cam. ALWAYS keep tension on the exhaust side of the chain!! Chain slack goes to the intake side because that is where the ACCT is.
Here is a picture after the cam mod was done on a yfz450.


Thanks YFZ450Lynx

Please look at where the punch marks are on the gears before you start removing anything, as if you purchased your yfz used many have already done this mod.

Once you have the cam towers and half moon clips torq to spec (get a manual I convert foot pound to inch pound 7.2ft lb or "86.4 inch pound") turn the ACCT to place tension back on the chain! If your chain is sitting on top of the teeth and not where is is supposed to be, recheck that you have done everything correct. Slack goes to the ACCT side, never the exhaust side. Please do not count pins as the only way to do the cam mod. This is where people can get off track in doing the "mod". If you choose to count pins, mark the gears and chain, and please take note of the pin count before and after the "mod" only to show that it has been turned 1 tooth. Then replace the copper washer and end bolt. TQ to spec (7.2ft lb or 86.4 inch pound).

Now rotate the crank counter clockwise a few revalutions to make sure that nothing is wrong and that you have done this mod correctly. Recheck that your cam timing and punch marks are where they should be! Rotate again! As this is the part some people mess up.

Replace all that you have removed to do this mod back where it goes. Cam cover/ vacume hoses/ carb/ boot/ gas tank etc.

Rotate the crank by hand again counter clockwise.
Now if there is NO binding or "funny" noises, feel free to put in a new spark plug. Ha Ha. I bet you thought I'd say to fire it up

Rotate it again!! If there is no binding or anything hitting then you are good.
Now you can fire it up. If done correctly it will sound and feel just right.

This mod gives you an inrease in power in the mid to upper rpm range!! NOT in the lower rpm range!

I did notice that my motor does not run as hot and the fan does not come on with having the cam mod done. My fan used to come on all the time.
I hope that this write up gives some one the basic before hand knowledge to know what is involved. It is not a step by step. That is what the manual is for.
Some people have had to increase their pilot jet/ or needle clip postion. I did not.

Good luck!
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Old 11-15-2006, 08:21 PM   #2 (permalink)
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Good job. Pinned it up top.

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Old 11-15-2006, 08:55 PM   #3 (permalink)
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This should be pinned in every sub forum also...including the lounge.

Great job tersejr.
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Old 11-15-2006, 08:59 PM   #4 (permalink)
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Thank you to all the members who donated their time and effort into helping me with this write up and providing pictures.
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Old 11-15-2006, 09:08 PM   #5 (permalink)
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Well done Eric
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Old 11-15-2006, 09:42 PM   #6 (permalink)
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Very well written, to the point and easy to follow. Heck, even I could do it. Thank you for taking the time to create this.
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Old 11-15-2006, 10:16 PM   #7 (permalink)
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Nice work! :)
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Old 11-15-2006, 10:26 PM   #8 (permalink)
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Nice job. Very well written. Now HOPEFULLY we won't have anyone asking us how to do this.
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Old 11-15-2006, 11:28 PM   #9 (permalink)
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Just a tid bit of info on the cam mod... I did a search for "cam mod" and 24 pages and over 1,000 posts came up
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Old 11-15-2006, 11:49 PM   #10 (permalink)
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"so i just got my 07 YFZ and i want to know what the cam mod is and how you do it can someone explain" lol maybe these will start to go away. nice job tersejr
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Old 11-15-2006, 11:50 PM   #11 (permalink)
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Quote:
Just a tid bit of info on the cam mod... I did a search for "cam mod" and 24 pages and over 1,000 posts came up
[/b]
But what about counting the pins?
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Old 11-15-2006, 11:55 PM   #12 (permalink)
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Quote:
But what about counting the pins?
[/b]



I see 14 and 13
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Old 11-16-2006, 12:02 AM   #13 (permalink)
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I just had to be a smart a$$. Great job!
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Old 11-16-2006, 03:22 AM   #14 (permalink)
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Quote:
Just a tid bit of info on the cam mod... I did a search for "cam mod" and 24 pages and over 1,000 posts came up
[/b]
Nice one, well set out better than any workshop manual I ever red!!
Two questions First how does this affect warranty with anew bike?
Second (though i expect this has been asked a thousand times) Why don't yamaha do this as standard from the factory??
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Old 11-16-2006, 06:35 AM   #15 (permalink)
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Good work, hopefully this will clear things up



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Old 11-16-2006, 01:55 PM   #16 (permalink)
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The warranty will not be affected because the cam mod is the Yamaha factory timing in the YZ450f dirt bike. As long as the cam mod is done correctly there will not be warrenty problems.

Yamaha wanted a more controlled power delivery and not as abrupt. The yfz quad stock timing is exactly the same as the WR450f dirt bike. That bike was designed for controlled power where as the yz450f bike needed a more aggressive power delivery for mx.

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Old 11-16-2006, 05:17 PM   #17 (permalink)
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Good job
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Old 11-16-2006, 06:53 PM   #18 (permalink)
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I just wanted to add this in here since I wen't through it myself... hope it helps...

Quote:
Ok, tore the thing apart again this afternoon in 5 minutes! ... and found what we are talking about.

to clarify yes there is a thick and thin side of the circlip. no we don't know if it matters which way they are ut in, but we do know the way they come from the factory.

As alba450 stated, the fat side of the circlip goes towords the throttle side of the bike the skinny side should be otwords the cam chain when installed.

Here are a couple pics that you can actually see the thisckness variation of the circlip.





Again, thanks for all of the help guys.[/b]
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Old 11-16-2006, 08:32 PM   #19 (permalink)
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Thanks alot for adding those pictures
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Old 11-18-2006, 10:28 AM   #20 (permalink)
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i read this last nite and did the mod in my shed in about a half an hour. this article was great if it wasnt for this i wouldnt have done it. i think i need to change my needle to make it richer though it kinda bogs down low when i crack the throttle. any tips would be appreciated and again thanks for putting this up!!!
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