OK, I am going to post here my experience putting the front and rear suspension for a YZ 80 onto a TTR 125.

I am using parts from a 1994 YZ 80. In researching on this site that is the oldest YZ suggested to steal parts from for this swap.

Also, I bought an entire YZ 80 with a bad motor, so some steps for me will be easier that trying to get the L model wheels and brakes to work since I am using 100% of the front end from the YZ including wheels and brakes.

I will do the same when I start with the back, but that is comming later.

The front end is almost a direct bolt on which makes this a very easy swap. The TTR and YZ use the same lower stearing head bearing. The headstocks are slightly different lengths, but because the YZ is longer you can make it work on the TTR by using a shim to take up the little extra length.

I have not detailed every single step. I only highlighted what I saw as issues and differences.


The first thing I wanted to see was, people use the caged ball bearning on the top in this swap, I wanted to see whay the tapered rollers from the YZ do not go in top and bottom.

So first, you must get the races out of the YZ frame (since you will need at least one of them for the top of the TTR if this works.

Here is a picture of the YZ frame after I tapped out the race. Use a good punch and alternate around the race to drive it out evenly.



Here is a picture of what the headstock looks like without a race, nice square surface for the race to seat in.




Next I measure the headstock to see how deep the recess was for the bearing race.



14 32nd's of an inch.



The depth of the recess on the TTR is only 8 32nd's of an inch (Trust me)



But even worse news was that the race is smaller in diameter. So no possability of using the YZ bearing for the upper too. (yea I know, blurry picture)



Next you need a spacer. The headstock on the TTR is shorter than the YZ. People have been using washers, but I wanted something a little nicer. I had a piece of 1/4" aluminum stock left over from another project so I made a spacer out of that. I went down to the hardware store and got a hole saw. I needed a new one anyway because I lost the arbor to the one I had. Anyway I got a 1 5/8" for the outside and a 1" for the inside.



I used a drill press to keep the cuts square.



And since the hole saws use a pilot bit, I was able to cut the second hole exactly in the center of my first one by putting the pilot bit back in the same hole.



And here is my new spacer. Better than washers because a stamped washer will not be as flat as this is which will help keep pressure on the bearings even. And this is lighter that two or three steel 1" washers.:busted:

So here is the washer in place ready for the bearing preload to be set.



The start button is on the back side of the front brake clamp. The YZ front brake uses bigger bolts, so I had to CAREFULLY drill out the holes on the starter button for the new bolts to fit. I also went down to the hardware store again and got some alen head cap srews because the stock screws had shoulders on them and would not fit in the recess of the starter button shell.



So here is what she looks like now. Disk front brakes and aluminum rims on the old TTR.



I also had to re-drill the holes in the front fender to get it to mount, the YZ holes are spaced a little wide. I used the front fender from the YZ as a guide to drill.

Nice work. I used the washers but having a spacer like that is much cleaner indeed.

did you use the front wheel from the yz80 What Iwant to do is...get a 19'' wheel in place of the stock yz80 wheel. do you think that that's a better way to go.