How to do the yz/ex conversion.

[Mxbubs]

READ THIS THREAD IN FULL BECAUSE I AM ALWAYS EDITINGIN IT AND ADDING TO IT AS I TWEAK OUT MY BIKE. CHECK FOR UPDATES AND CHANGES WITHIN IT.

How to do the yz/ex conversion.
Before you begin anything, you need to become good friends with Mcmaster-Carr.com. They will have most everything you need. You will need a good welder, and a good machinist can save you alot of money from having to be ripped one by EastcoastAtv.

Here is a nutshell of the obstacles.

You will need 2" flexible air duct hose to make the carb boot work with the Ex stock setup. (Jcwhitney.com)

The motor needs to move to the left exactly .600 thousands, or six tenths of an inch.

You will need to build a custom oil rezzy, or you can use your stock ex rezzy buy mounting it to the back side of the replaced vertical bars behind your radiator (you'll see).
You will need to weld mounting tabs for the bottom center motor mounts, and for the top (head stay).

The ex pivot bolt is too small of OD to fit snuggly in the pivot bolt hole of the motor, so you will need to knock the two bushings out that are already in the hole, and replace them with a custom machined bushing/sleeve that is 3.5" long. I forget the exact OD and ID of the bushing, but 3.5" long will fit everything snug.

Added 4-07-03. Or you can buy a 5/8" bolt at the hard ware store, and use it. It will fit snug in the yz426 case/bolt hole. HOWEVER, you will need to drill the frame out, and drill out the swingarm needlebearing bushings/spacers. The only way to drill them out is with a chromed MASONRY bit. The spacers/races are so hard, they will eat up a regular bit. If you gusset the pivot area, I would go with the 5/8" bolt.

You will need a grinder, buy a good one. A dremmel would also be a good idea.

The Kickstarter needs to come out exactly 2.5". The cheapest and a good way to do this is simply buy another splined knuckle from yamaha, they are 30$, have a sleeve made exaclty 2" long and weld the sleeve between the new one and the one you already had. The take a grinder and cut the kicker mount off the one closest to the motor, you wont need it. If you have a good welder, this WILL work and WILL not break. I have a friend that gave me this idea.

My oil rezzy is3.5"X 3.5" by 9" long....You can go longer, but I dont think you can go much wider, I couldnt go any taller because of my big radiator. That size rezzy gives me about 1.75" quarts of oil in the rezzy, and then I add some more once the motor gets its share. (Kinda like the 400ex) The stock yamaha bike calls for 2 quarts, fyi. You can buy 12" by 12" sheets fo aluminum from mcmaster-carr.com, as well as the nipples to weld to it for your fittings.

On the water input side of the motor, the fitting on your water line going into the motor is a Y fitting, and this will not work. You will need to get the output side hard pipe that from Yamaha for about $30 and cut it off real short. It is a 90 degree piece, slide your hose up on it and clamp it down. It will miss your pipe fine.

Baldwin makes the throttle cables for 30$.
Trinity makes the custom pipes for 430$.
I think trinity sales the mounts identical to the ones I have. I got mine from Adam, the front bottom mount tabs (ears) is what I am refering to.

[Mxbubs]

You can see the 3/8" nipple welded to the top for the oil line coming out of the top of the motor. Your input side for your motor oil is on the right side of the motor, you have two outputs, one out of the top and one on the bottom left of the motor, like the 400ex.

Be very careful when welding your drain plug. (bottom right), if you weld it sticking out too far, it will not slide in easy between your vertical frame supports, and if it sticks too far down, you cant get a wrench and bolt in the nipple because it will be too close to the bottom frame.

[Mxbubs]

If your oil can is mounted too far forward, your stem will lobe will rub it....Look at the arrow on the left.....I goofed up and didnt realize this, so I had to make some tabs to move my oil rezzy back, I didnt want to cut and grind the tabs I had welded to the frame because I had already powdercoated before I goofed up, so I just made up for it by adding tabs to the front of the oil rezzy as seen by the arrow on the right.

[Mxbubs]

Again, this is the front of the rezzy. I got some aluminum spacers, by the way, alot of hardware stores carry aluminum and steel spacers, did some grinding on them, my oil rezzy fits very snug, its not going anywhere. I used the aluminum sleeves from the top of the motor mounts on the ex motor to weld to my aluminum rezzy. You will not need them for the top motor mount on this motor.

[Mxbubs]

Here is your oil rezzy fill. I used 3/8" couplings for the 3 oil line fittings, and I used barbed brass nipples coming out of the 3/8" couplings and just slid my hoses over them, they have yet to leak.

You can see the spacers, they are .600. Moving your motor over to the left lines up your sprockets.

I used 1/2 aluminum couplings for the drain and fill.

[Mxbubs]

There is only one spacer on the bottom right side, and it is .660 thousands, you dont put any spacers and the bottom of the mount tab to the frame.

Oh yeah, make sure you elevate your rezzy so it will go over your nerf bars, and make sure it isnt too high to where it wont fit because of your radiator.

[Mxbubs]

Here is the spacers I used on the bottom center to help hold the motor from moving left to right. Notice how they are cut in half on one end so they dont hit my frame tube, instead they butt right up againts the motor tabs I welded to the bottom of the frame on each side. If you really want a snug fit, slide a washer or two between the spacer and motor.

[Mxbubs]

The left side bottom spacer.

[Mxbubs]

This is the oil line output of the motor and back into the rezzy. (bottom left side of motor) It took some serious bending but I got it to work. It does not leak. NOTE: USE TWO PIPE CLAMPS!

[Mxbubs]

Right side oil line, motor input.