Creating the YZ125F

[XRpredator]

I got a swinging deal on a 1998 YZ80 that a guy was all too happy to get rid of. I think everyone knows my lack of love for the two-strokes, but this has the suspenders I want for Pred2's TTR125.

Yesterday I decided to tear into the pair of machines and at least get the front suspenders on the TTR. It was almost magical how easily it went together.

Some items:

• The steering spindle on the YZ80, while exactly the same diameter and length as the TTR, has threads in a slightly different spot, necessitating some washers to make it fit proper on the TTR.
• The YZ top clamp puts the bars further back than they are on the TTR. This makes the key for the ignition on the E-start not quite fit the same.
• The choke button has to be moved to one side to make room for the key
• The top bearing on the TTR (balls in a plastic retainer) is not quite as rugged as the roller/race top bearing on the YZ, and the balls will fall out if you're not careful, but it works.
• Not having the torque specs for the YZ clamps is bad, as the top clamp bolt can't withstand 18 ft-lbs without snapping :bang: There will be some sort of replacing going on there.
• TTR front fender doesn't match up to the holes on the bottom YZ clamp, and the YZ donor fender is boogered up good. Replacement necessary.
• The forks are obviously longer, and rake out the front end a bit. Didn't notice a lot of gain in ground clearance. There will be some playing around with raising the forks in the clamps.

I'll post pictures later.

Next part of the project . . . Making the YZ swingarm/brake/rear wheel combination fit the TTR. If ANYBODY has any clues as to how this can be done, let me know!

 

[kawicam250]

sounds like a lot of work, but it'll be worth it. and yes, im very surprised that youre even considering messing with a 2T :) . good luck and i look forward to seeing some pics :cool: .

 

[IndyMX]

I wonder how difficult it would have been to try putting the TTR motor in the YZ??

 

[kawicam250]

Pred, you could ask AJ for some advice, seeing that he has done this transformation only with bigger motors and frames several times :nod: .

 

[XRpredator]

I wonder how difficult it would have been to try putting the TTR motor in the YZ??

too many other variables, and since the forks basically bolt right up it's all good. So far there hasn't been any welding at all.

 

[2 strokes for life]

XRpredator, but welding is fun. Keep us updated on you proggres.

 

[Patman]

Pred I'd seriously look at fitting a roller bearing setup to the TTR stem.

The YZ fender will very likely hit the frame or head pipe on the TTR. Nothing a little trimming and heat gun work can't easily resolve.

The rear suspension is a bit more involved. Take things apart and measure/test fit then scratch your head a bit. Then repeat the whole process a few more times because it's a lot better than this process :bang: :bang:

 

[XRpredator]

Pred I'd seriously look at fitting a roller bearing setup to the TTR stem.

I've thought long and hard about that, but for now the top one will be hunky dory (Pred2 is not the most abusive of riders).

The YZ fender will very likely hit the frame or head pipe on the TTR. Nothing a little trimming and heat gun work can't easily resolve.

I thought it would, but amazingly it clears perfectly, and gives me a bit more coverage from mud and goo on the engine. Of course, it might hamper cooling *shrug*

The rear suspension is a bit more involved. Take things apart and measure/test fit then scratch your head a bit. Then repeat the whole process a few more times because it's a lot better than this process :bang: :bang:

You ain't kiddin', my friend. Not only do I have the swingarm issue, I gotta figure out where to put the rear brake master cylinder and how I'm gonna work the plunger with the stock TTR pedal (I think I got a plan for that, though ;))

 

[Patman]

If heat get's to be an issue Dremmel makes this really cool fender customization & perforation tool.....

 

[DougRoost]

too many other variables, and since the forks basically bolt right up it's all good. So far there hasn't been any welding at all.

I have to wonder if the forks fitting in the TTR were to trick you into trying this approach. Besides, isn't a weak frame one of the problems of the TTR125, or had you already invested in BBR's engine cradle?

 

[XRpredator]

the frame cradle is on the short list of items to purchase. I see BBR has a forged version nowadays . . .

But like I said, stress will be minimal by Pred2. I hornswaggled my Delicate Flower into thinking this was all to make the bike better for the boy, and it'll hopefully grow with him for one more year, but mostly it's to make it a sweet playbike for me ;)

By the way, there will be some miscellaneous parts for sale soon, from stock TTR forks to a complete YZ80 engine . . . in the for sale forum, of course. :nod:

 

[XRpredator]

I promised pics, so here they is. The Donor, and the Recipient

 

[XRpredator]

now, the donor on top, recipient on bottom

 

[XRpredator]

Pred2 wasn't excited when I showed him his new motorized unicycle . . .

 

[XRpredator]

here's the YZ forks installed. Note the two big ol' washers needed to shim things up proper-like

 

[XRpredator]

notice the easy 1/2 inch gain in ground clearance, and a pic of Pred2 holding it up, just for giggles.

 

[XRpredator]

Today began the teardown of the rear end on the YZ. No real issues taking things apart. The swingarm does mount differently than on the TTR, so I am a bit worried what I'm going to do. Also, the linkage is a bit different, and I'll have to do some fabricating on the brake pedal and the master cylinder mount. More on that later.

Here's the semi-stripped down donor and the rear suspension assembly. Anyone need a YZ80 engine?

 

[2 strokes for life]

Man i like the bike. How much are you wanting for the 80 engine.

 

[XRpredator]

Man i like the bike. How much are you wanting for the 80 engine.

http://www.dirtrider.net/forums3/showthread.php?t=151139

 

[2 strokes for life]

Alright. nSo how well is the rear coming along.

 

[XRpredator]

pictures soon. There's a few holes to be drilled and some welds to make.

Hopefully it will be done by this weekend, depending on the weather

 

[Rich Rohrich]

Pred - I'll box up that frame cradle I have for you and get it sent in the next day or so.

 

[XRpredator]

Rich, you are too much awesome. :cool:

 

[kawicam250]

looks like its coming along, between you and Rich, it shouldnt take too long :nod: .

 

[XRpredator]

Okay, got the swingarm mounted, everything bolted up 'cept the top shock mount. Time to do some cutting and welding so the shock will fit, and then the disc brake master cylinder mount, reservoir mount, and brake pedal mod.

The y-shaped linkage had to be flipped over, and a small dogbone from the TTR needed re-used at the front. Allegedly it has to be welded to the frame, but I'm going to see how things work first.

I'm also a bit worried about airbox fitment after I get the shock mounted, as well as the battery box.

Keep your fingers crossed.