08 yfz 450

[86T3]

I just got this last week and im pretty excited about it. I got a real nice deal on it cause the case is cracked where the shift shaft comes through. I found tthe only used left side case on ebay, made an offer and have it already. I was looking for a used one because the new ones are sold in pairs only. They're only 380 ish for the pair but i figured if i could save some money on new cases i can get some other goodies. Im planning on having someone do the case swap since i have a habit of losing interest mid project. I want to have the cam timing advanced while its open as well. I want to get it running soon to make sure everything is right with it because its going to go to pensylvania in september for the next phase :naughty:

174692

[KASEY]

if you just got it,,,WHY THE HELL would you mess with the cam timing???? if its because someone said its better I say BULLCRAP ,,,,,, I been running a yfz for 8 years and I see no reason to switch it,,, and the benifiets are only above 10,000 rpm's ,,, not worth it,, trust me,... they cost $$$$$$$$ to repair a blown up motor,,, I know I am building one right now,,

[stroberts22]

You don't advance the timing, you retard the exhaust cam by 1 tooth and it really wakes these motors up by giving it timing closer to the yz450f. I did it to mine and rejeted it and done the mod to the accelerator pump to get the off idle stumble out of it and it a total different machine. Rossier has a good step by step directions.http://www.rossiereng.com/wp-content/uploads/2012/09/retarding_yfz_cam1.pdf

[86T3]

Well, i talked to my buddy who s going to swap the case for me and he pretty much said exactly what kasey said. He also said that it makes them harder to start. How does yours start stroberts? So i guess the plan now is to just disassemble, inspect, and reassemble. Im going to order the gaskets today and pull the motor this weekend.

[hippyplz]

I haven't had any luck doing the cam mod on anything newer than 06. Our 05 loved it, but nether of our 07 would even start and the same for a buddy 08. The yfz is alot of great thing, but cheap to rebuild is not one of them.

[Poco Loco]

I agree with Kasey, Ive been riding and racing mine sense 11/2003. Those motors are fast rite off the showroom floor. Pipe , intake and a K&N and jetting and your in. Reliable power.
if you just got it,,,WHY THE HELL would you mess with the cam timing???? if its because someone said its better I say BULLCRAP ,,,,,, I been running a yfz for 8 years and I see no reason to switch it,,, and the benifiets are only above 10,000 rpm's ,,, not worth it,, trust me,... they cost $$$$$$$$ to repair a blown up motor,,, I know I am building one right now,,

[stroberts22]

My yfz is a 07 and it starts with just a slight push of the starter button. If it's hard to start the valve lash needs adjustment. My particular setup, it works well and could actually tell the difference in the seat of the pants after I did the mod and it's free. I would also send the head off and have the valves done. The valves beat the seats up and this causes the valve lash to get tighter and you run out of adjustment. My motor has never been apart and the head is screaming for some attention. Racers keep up with how many hours they have on them and rebuild them regular. Mine is on borrowed time. I'm going to send mine to Rossier before winter xc season.

[86T3]

Got some bad news today. The shop thats swapping the case for me found a crack in the piston and that the rod bearing is on its way out. Any advice for a piston and rod? I want to be able to keep running 93 octane in it so i dont know if i can even put in a higher compression piston. Any rod brands to stay away from? Keep it all oem? Its also getting a new timing chain, shifter shaft and a shift fork. The wheeler isnt looking like such a deal anymore but atleast ill know the engine will be sound

[SWIGIN]

I have a YZ426 motor big bored to a 444 with a 13.5-1 JE piston both hotcams and lots of head work and it runs perfectly fine on 93 pump gas.

Use that info as you will.


I would only use OEM crank parts but that's me, look into the oil mod for the rod.

[86T3]

Thanks for the input. After researching in on the yfz forums and separating all the crap information that idiots post there i decided on a 12.75:1 CP piston. Apparantly the compression ratio for these pistons is a bit lower in 06+ engines so it will wind up being somewhere around 12.25:1 which is where i wanted to be. I also ordered an oem rod, bearing and pin.