The recent mishap to the "Glamis Dunes project bike" gave me the notion to tear mine down to see how things were going inside my YFZ. Granted, this bike ran perfect when we shut it off in May. Its an 04 with mucho mucho hours on it, but I bought it used and have only put about 20 hours on it myself. I did the 2007 side case conversion to it about 10 hours ago to help with lubrication, but think I think the damage had already been done by that point. Plus......on top of all the hours the previous owner had it jetted way too lean and also ran a cheap Alba rev box on it. Those things do some crazy shiat to the timing that Im sure the motor does not appreciate.

Upon tear down everything thing looked great. No gauling at the wrist pin, the bore looked brand new with all cross-hatching, the piston shirt showed very little waer, and the crankshaft had zero slop.....at least visually. I was starting to think I wasted my afternoon.

And then I noticed...........

Here is a funny comparison. Stock 2004 TRX 450 piston vs Stock 2004 YFZ 450 piston. If you've ever wondered why the 04/05 TRX 450 revved so slow compared to a YFZ here is why......

Good call on the tear down. That could have caused some "issues"
Good luck with the rebuild.

PDR

Im all over it. Infact, I sent you an email on your website about some parts.

Also, Im searching all over the net for a WR 12.5:1 CP piston and don't seem to be having any luck. Do you know if Velocity or Wicked makes one? If not i'll just stick to the stock WR piston........but I REALLY like the features of the CP's.

Hurry up and fix it so i can ride it again. haha

CP itself does not make a 12.5:1 WR piston. They make a 13:1.

Wicked only makes the 13.5:1 piston. I have no idea what velocity has for that compression. There is also the venom piston.

PDR

What is the octane requirement with the 13:1 with a thick base gasket?

probably around 98-100. I have heard of people running it with pump gas, like 93, not our 91 we get here. Its more than likely not worth even trying it if you want to straight pump.

couldnt you put in a stock YZ450F piston? 12.3:1? same Bore x Stroke 95.0mm x 63.4mm
but that is an 2006-07 im not sure what the 2004-05 stroke and bore is. i believe it is different?
bummer about the quad. well I believe to have alot of hrs on mine. I know i've abused it. just dont want to tear it down unless there is a problem.

Well I am going with a WR450 crank, and if my research is correct the WR rod uses a piston with a 18mm wrist pin, whereas the YFZ and YZF cranks utilize a piston with a 20mm wrist pin. So you can see why my choices are limited to a WR style piston. And I REALLY REALLY like the features of a CP piston. Its a far superior design. You may pay a little more for one, but ive learned the hard way a too many times.........you get what you pay for.

As far as tearing your bike down, I wouldnt bother either. Plus youve owned yours since it was new so you know how its been treated this whole time at least

I wish i had a book of length of yamaha cranks and rods. maybe there is a rod that has the right side rod rournal to fit the wrcrank and the wrist pin of a YFZ/YZF... reminds me of small block chevys.

The YZ and WR both have a 18mm wrist pin.

PDR

Diesel

wow...





damm good catch right there!!!

Bling!
My piston search just got easier.

The issue is that 12.5:1 is the stock compression on the YZ and WR bikes. So, CP does not feel the need to make a stock compression piston. Kinda odd, but they just dont have the market for it. The guys doing the custom CP pistons may have some made, not sure. Wicked only has teh 13.5:1 compression. Definitely check out the Venom Pistons man.

PDR

Put a carillo rod in while you are at it

Hey, I was on the phone with CP the other day and I was told that there is a 12.5:1 piston available.. give them a call and talk to them over there I'm sure they can recommend some setups.. I just got my CP piston and I can't wait to get my build going.

I'f you are doing a build you might as well do it right... I was against the idea of race gas also but hey... I would only use at most 10 gallons in a weekend... and thats riding ALL weekend

Oh and Diesel, I'll be calling you soon for the oil mod kit!

10 gallons is a day and moring run... dam, im gonna be the one with a slow 450

Yeah, I saw that 12.5:1 piston too but that is for the YFZ style rod. I think I am going to go with the 13:1 that CP offers for the WR appl. My beef with the race gas is having to drive over to Soco to get, not so much the price. So this year I am going to just get a 55 gallon drum and keep it in the garage. I found Sunoco 110 delivered to my house for $329.

I rarely use 5 gallons in a weekend. Where the hell are you guys riding to, Brawley and back? That reminds me of my banshee days when I would burn through a can of gas just going to the hill and back.

Thats not too bad, I'd be afraid that I would'nt be able to use 55 gallons in a season. I wouldn't want gas that costs 6.00 + a gallon going to waste.

I see what you are talking about with the WR, now I understand why its tough for you to fin the right piston

450 is geared low in the sand, not good top speed (you know cause of the drags) hit the tank hard!

It sounds like alot, but this is fuel for my TRX and her YFZ.

I thought you said you added a 15 tooth front sproket?

whats the word PHIL? did you get it running? what did you end up with as your final build?

I got the motor buttoned up and then took off out of town for vacation. Its all just cosmetics from here. I am sure i'll have it started sometime this week.

Nothing crazy, it's just my wifes bike. I stayed with the 12.5:1 CP piston. I think i'll setup the gearing a little taller too. YFZ's seem to be all over the rev limiter with stock gearing. Other than that she's ready.

Now the Honda is a different story. I need to get my ass in gear if I am going to make that Sept ride.

that would be nice (and have a/c )