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TTR-YZ Fork Swap How-To

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Many have professed interest in what it takes to swap the TTR125's forks out with a YZ85 model. The forks/clamps combo can be found on E-bay for around $300 roughly. Many of the other pieces may come with the set, so don't rush out and buy any parts before you get your fork set. I figured when I did mine, I'd take tons of pics and post the step by step directions, so here goes-

What you will need-

1.Front Fork Tubes from a YZ 85

2.Upper and Lower triple clamps from a YZ 85

3.Retainer nuts for the stem from YZ 85

4.Front axle and nut from YZ 85 from years 93-06

5.2 Grade 8 washers with 1" center hole

6.2 small washers that fit around the axle shaft.

7.YZ 85 front brake line (the TTR one comes up short, but can be used.)

8.Lower steering stem bearing from YZ 85

9.Lower fork guards form a YZ 85

10.Brake line mounting from a YZ 85

The tools you will need are-

1.Good metric socket set.

2.Spanner wrench or Brass punch

3.Torque wrench that goes as low as 15 ft lbs and up to 80 ft lbs

4.Plenty of clean rags

5.Some good quality bearing grease.

6.Wooden or Rubber mallet

7.Good sturdy bike stand-I made my own.

It's actually a lot easier than it looks, it bolts together quite quickly, it took me about 2 hours, and that was taking notes to make this post.

Start off with removing the number plate and the bars, don't take anything off the bars, just remove them from the TTR upper clamp and set them aside- TTRForkProject012.jpg

Next, remove the upper steering stem nut that retains the upper clamp and loosen the pinch bolts. Remove the upper clamp at this point- TTRForkProject016.jpg but don't hit it with a metal hammer, use a wooden or rubber mallet.

Press the brake pads back into the caliper with a scredriver so that the front wheel will be easy to reinsert. Do not remove the brake line from either end, just swing it out of the way. Remove the caliper, front wheel and axle, save the front wheel, axle spacers, and seals and bearings, we will be reusing those- TTRForkProject026.jpg

Next, we need to remove the upper steering stem retainer nuts-

TTRForkProject020.jpg

A spanner wrench is the ideal tool, but you can use a brass punch if one isn't available, DO NOT USE A STEEL PUNCH-it will damage the notches in the nut.

Now, the entire front end will slide out as one piece, with the forks still attached to the lower triple clamp. Here is the difference between the two sets of forks and axles side by side- TTRForkProject006.jpg

Now, clean the frame out thouroughly with some rags and brake cleaner to remove all old and dirty grease, and allow it to dry. Clean up and save the TTR top bearing, as that will be reused, and the YZ lower bearing, which is pressed onto the steering stem.

TTRForkProject008.jpg

Work grease into the lower stem bearing from the YZ, and the upper ball type bearing from the TTR. Grease the steering stem shaft lightly, and put a light coating on the inside of the frame, too-this will prevent rust- TTRForkProject009.jpg

Slide the YZ forks along with the the lower clamp and stem with the YZ 85 lower bearing installed up into the frame, then install the TTR upper bearing from the top, reusing the TTR top seal and thin plate, then install the 2-1" diameter Grade 8 washers onto the stem, then the cog nut. The YZ setup only uses one cog nut, and torque it to 27 ft lbs, then turn it right and left several times, then back it off one full turn and repeat turning many times. Now, torque it to 14 ft lbs. TTRForkProject011.jpg

Place the upper clamp on, and reuse the TTR top clamp nut and torque it to 80 ft lbs.

Install the bars next, and torque the bar caps to 17 ft lbs.

Now move the fork tubes up as far as they will go in the clamps without hitting the underside of the bars and tighten the upper and lower pinch bolts TTRForkProject021.jpg This is because the YZ forks are MUCH longer than the stock TTR's and will cause the bike to ride nose high if you don't.

Now, reinstall the original TTR front wheel, using the YZ 85 axle, and the TTR spacers and seals. Place the 2 small washers listed in the parts list on the RH side (if you're sitting on the bike)-that's the opposite side as the caliper. These keep the brake rotor properly aligned with the caliper.TTRForkProject019.jpg Torque the front axle nut while holding the bolt stationary to 32 ft lbs.

The TTR front fender may be reused, but you will have to do some drilling as the bolt holes don't line up, I used the YZ 85 front fender, it's larger and provides more protection from slinging goo- TTRForkProject025.jpg

The TTR stock number plate lines up perfectly with the mounting holes in the YZ fender, and the upper bolt hole is in the right place too! :devil:

When installing the TTR caliper back onto the YZ forks, the bolts that go through the bracket are to be torqued to 22 ft lbs, and the single bolt that goes through the body of the caliper and into the bracket is to be torqued to 16 ft lbs.

The TTR caliper and caliper bracket bolt up directly, but the brake hose seems to be a bit short-

?action=view&current=TTRForkProject021.jpg&refPage=&imgAnch=imgAnch32

It went well, and here's my finished product- TTRForkProject001.jpgTTR125L3-24-07.jpg

And with the YZ 85 master cylinder and Stainless Steel front brake line installed-

TTRwithProtapers001.jpg

It doesn't have that front end "flex" or "wander" any more, but I need some heavier springs to make it right. It does ride a bit higher that the stocker, but not too bad if you move the fork legs up in the clamps.

It was real easy, and took around 2 hours to do. Next mod, YZ 85 swingarm, shock, linkage and hydraulic brakes!

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Great write up. Well done.

So where do you get and what size springs do you put in it?

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Great post. You get springs from cannon racecraft. You put in .36 for $100, and then you just smile. If any one needs some forks, I have a set of 2005 kx100 forks that will bolt right up, with the clamps, and spacers. These forks are great and have been rebuilt recently by active ride suspention.

100_1059.jpg

Pm me for an offer.

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So where do you get and what size springs do you put in it?

I haven't done anything with the springs or valving yet, but that's coming-I am trying to find, or have someone make me a set of .44's, as I'm a pretty big boy. Will let you know when I find someone to make them.

Springs are only part of the equation, valving for the type of riding you intend and your speeds you ride is equally important.

If you are going to do one, it only makes sense to do the other.

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Stupid question, but looking at your view from the front, it looks like the wheel is nowhere near centered...is this correct, or an illusion?

http://s94.photobucket.com/albums/l111/chickenhauler_2006/bikes/?action=view&current=TTRForkProject021.jpg&refPage=&imgAnch=imgAnch32

Anyone know if those KX forks will really work easily...or at least as easily as the above 85 mod?

I am really surprised that the stock front wheel from the TTR works, but that is a good thing, as I am about to buy Aluminum rims for the bike...

Mike

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Stupid question, but looking at your view from the front, it looks like the wheel is nowhere near centered...is this correct, or an illusion?

http://s94.photobucket.com/albums/l111/chickenhauler_2006/bikes/?action=view&current=TTRForkProject021.jpg&refPage=&imgAnch=imgAnch32

Anyone know if those KX forks will really work easily...or at least as easily as the above 85 mod?

I am really surprised that the stock front wheel from the TTR works, but that is a good thing, as I am about to buy Aluminum rims for the bike...

Mike

It IS a little off-set to the caliper side, the two washers on the opposite side do off-set it a small bit, less than 1/4", and it looks much worse in the picture than in person. The TTR hub is narrower than the YZ85 hub, thus the need for the washers, and if they are placed one on each side, the rotor will not line up properly with the caliper. If one uses the YZ 17" wheel vs TTR 19" wheel, then you would use the YZ spacers, and no washers, but lose 1" of ground clearance. If using the YZ wheel figure another $125 for the wheel. I'll get some better close up pictures of how it sits.

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Thanks for the straight up answer.

Now for another odd question...is there any reason to think that the front end (axle area) would be any less rigid, or risk of bending axle due to narrower hub?

Is the hub only 1/4 inch narrower? or are you saying that it is only offset by about a 1/4 inch?

thanks and sorry for the inquisition...

MW

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Thanks for the straight up answer.

Now for another odd question...is there any reason to think that the front end (axle area) would be any less rigid, or risk of bending axle due to narrower hub?

Is the hub only 1/4 inch narrower? or are you saying that it is only offset by about a 1/4 inch?

thanks and sorry for the inquisition...

MW

No problem on the questions, thats why we all come here.

The TTR Front Hub Vs YZ front hub is roughly 1/4" difference, I didn't measure it exactly with a micrometer.

I am not too concerned about the axle breaking or bending as it's solid, not hollow.

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It IS a little off-set to the caliper side, the two washers on the opposite side do off-set it a small bit, less than 1/4", and it looks much worse in the picture than in person. The TTR hub is narrower than the YZ85 hub, thus the need for the washers, and if they are placed one on each side, the rotor will not line up properly with the caliper. If one uses the YZ 17" wheel vs TTR 19" wheel, then you would use the YZ spacers, and no washers, but lose 1" of ground clearance. If using the YZ wheel figure another $125 for the wheel. I'll get some better close up pictures of how it sits.

Use two shims for the TTR hub like said but... use one on each side and poof your wheel is centered then shim out your caliper.

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Thank you very much for the in depth info. I could not have asked for any better. Great pics as well. 😛

I also have access to the front wheel and brake set up from the YZ. Any pros or cons regarding using the YZ units?

Have you done the swingarm and rear shock mod yet? I also have access to these and don't want to lose them if it's not too bad of a swap.

Thanks again for your help. :cheers:

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Thank you very much for the in depth info. I could not have asked for any better. Great pics as well. 😛

I also have access to the front wheel and brake set up from the YZ. Any pros or cons regarding using the YZ units?

Have you done the swingarm and rear shock mod yet? I also have access to these and don't want to lose them if it's not too bad of a swap.

Thanks again for your help. :cheers:

Actually, the YZ front brake is the way to go since the hose is longer and won't be cutting across the number plate like mine does, they both share the same front caliper, but the hoses and master cylinder are different (only in the hose connection points) so keeping the YZ front brake is great!

As far as the front wheel goes, the YZ hub, spokes, and rim are stronger, but smaller. Most YZ85's came with 17" front wheels, while the TTR came with 19" fronts, so you will lose 1" of ground clearance if using the YZ wheel. But that may be a good thing, then the bike will be more even front to rear:thinking:

I am still gathering all the YZ rear parts together (I'm cheap, want to keep the parts list under $200) and all I have left is the rear wheel. Might have to suck it up and shell out, as they aren't giving them away. So far I have the swingarm and linkage, new shock, and new entire brake system, for under $125.:bonk:

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Know I still want to know has any one put YZ, CR, RM forks on a TTR 230. If so how hard was it?

Thanks

The biggest question you need to answer is if the steering stem bearings are similar-if the donor and recipient bikes both use the same steering stem bearings, next, the length of the steering stem comes into play, if they are similar, then everything should fall into place.

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OK, I just landed a set of forks on eBay with the axle.

Now, I have a Tusk bar riser on my wife's bike raising the bars up about 1.5", shouldn't this allow me to level the bike out just about perfect while using the stock 19" wheel?

Also, if she is about 110 lbs and a trail rider only, will the regular 2004 YZ85 springs be OK for her???

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OK, I just landed a set of forks on eBay with the axle.

Now, I have a Tusk bar riser on my wife's bike raising the bars up about 1.5", shouldn't this allow me to level the bike out just about perfect while using the stock 19" wheel?

Also, if she is about 110 lbs and a trail rider only, will the regular 2004 YZ85 springs be OK for her???

You should be good with that setup just suck them up aways in the clamps. You might be real close with the stock brake line also if you dont have the YZ setup. The set I put on my bro-in-laws bike I did the same way, we didnt have risers but I moved them up all the way tell they about touched the bars, and he is running the stock front brake line and swingarm on his and it sits level. She should be fine with the stock spring rate for trail riding, I think its .26 or .27 but I cant remember.

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You should be good with that setup just suck them up aways in the clamps. You might be real close with the stock brake line also if you dont have the YZ setup. The set I put on my bro-in-laws bike I did the same way, we didnt have risers but I moved them up all the way tell they about touched the bars, and he is running the stock front brake line and swingarm on his and it sits level. She should be fine with the stock spring rate for trail riding, I think its .26 or .27 but I cant remember.

He's got it right, this setup will work, but the 19" front may hit the fender under hard bottoming (jumping way more than a TTR should with a fat man on board).😛

The bar risers will help lower the front, since you can move the forks up farther in the clamps, and will help alleviate the wheelie prone condition mine has-no complaints from me on that-I love it, but your wife might not.:cheers:

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I shimmed out the caliper instead of off setting the wheel in the forks to one side, i guess it would work either way, whish i had your post when bolting it up.

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