Modern Front end

[Jimbo31]

Hello everyone, I am a new member from canada looking to do a large build on a recently purchased 1981 xs400 special.

My Main alteration is that I want to put on some modern gold (preferably r6) forks but am not sure about the complications mainly with fitment of the triple tree does anyone have experience with this and is there better or worse forks to use?

thanks for your help!

 

[JARichmond]

Do a search for fork upgrades that will fit and xs. There was a thread posted not too long ago about it that should show up in the search box.

 

[bentwrench]

Anything is possible with enough time, money and skill. For that level of modification, you may also want to check out the www.dotheton.com forum, where they do crazy modifications on vintage bikes all the time.

In a nutshell, your biggest issue with a fork swap is the size of the yoke spindle on the new front end (the middle vertical bar that runs through the middle of the triple trees), and the size of your headstock (the hollow tube at the front of your frame that holds the front end in place.)

And by size, I mean length.

If the front end spindle is exactly the same size as the yoke on your frame, then you can drop it in with no modifcations. I can tell you now that there are no modern USD forks, gold or otherwise, that will do this for our bikes.

If the spindle is SHORTER than the headstock tube, well then you have to not only find a front end, but also a tube, hack your frame to bits, weld the new headstock on, and man, that's a lot of work, and has so many chances for failure that I don't even want to think about it.

Which means that you need to find a front end that has a LONGER spindle than your headstock. The bar on the front end has gotta reach all the way through the tube, right?

Then, you have to find a machinist (if you aren't one yourself) and build a spacer to fake your headstock to match the length of the spindle.

Then, you just need to get a set of custom bearings so everything will roll left and right.

THEN, you have to make sure that all the controls, electrics, etc. all match up and work - you can try to use the ones that came with the front end you found, or buy aftermarket everything.

AND THEN, you have to sit back, look at your bike, and hope like heck that the new front end isn't too long or too short. If it is, start over. In fact, do this part first, come to think of it.

AND AFTER ALL THAT, after many hours of work, money in parts and time scratching your head, you will have an awesome little bike that cost you thousands of dollars in time and parts, but which is freaking awesome (but likely only to you - trying to sell a 400 with a frankenstein suspension for more than it cost to build is highly unlikely.)

Trust me, I've been thinking about and researching this little mod myself, and decided it's just not worth it.

But here's some reading material if you want to pursue your dream (and who am I to piss on another man's dream? No one, that's who.)

http://www.bikers1.com/mhst.htm
http://www.dotheton.com/forum/index.php?topic=5669.0

Welcome to the board!

 

[Jimbo31]

thanks so much! that new website is helping a lot.. I would love the modern front end look but now im also looking at other more practical options as well

 

[bentwrench]

The easiest ways to tighten up our front ends is heavier weight fork oil, new springs, and a fork brace.

Then, just ride the F out of it.

 

[DanMach]

Sometimes I wonder if BW does much of anything but sit around absorbing endless amounts of xs400 info.

 

[bcware]

I just used heavier weight oil and the original fender as a brace. I also have highly sprung rear shocks and over sized tires. Overall the bike handles exceptionally well.

I don't have any chicken strips.

 

[CadXS]

Aprilia RS125 forks fit straight on with just one bearing change and look the business.

Picture on them on my bike during the build.

 

[bcware]

What about the wheels? Are those stock? Did you need new spacers?

Is that a stock swing-arm you had braced?

 

[CadXS]

They are stock wheels. If you want to keep the stock front wheel the wheel bearings need replacing with ones with 20mm id to match the Aprilia spindle and a new bearing spacer and new wheel spacers cut to size. Fitting the forks is simple, getting everything else to work with them is a challenge but not technically that difficult.

The swingarm is a stock but stretched about 2.5" and under-braced for strength and because I thought it looked cool...no other reason really

 

[bentwrench]

Sometimes I wonder if BW does much of anything but sit around absorbing endless amounts of xs400 info.

Yeah - I spend more time learning than I do riding...

 

[frwinks]

Hey Jimbo, don't give up just yet. Try to source early 90's crowns that fit your USD tubes. Mine only needed a 5MM spacer under the lower bearing to keep the lower lip of the head tube off the lower crown. With a set of tapered bearings it was a bolt on swap. I can get you the part #'s for the 20mm wheel bearings you'll need for your mag wheels. The only thing left will be the brakes, and there are a TON of options there. Good luck, and if you need any measurements, lmk

 

[XSLeo]

Bentwrench described one way to get a different frok on your bike, another is to get the fork you want, remove the stem, from the xs400 lower tree and the stem from the new tree and put the xs400 stem in the new tree. This rquires grinding out the welds and pressing them out. If the new tree has a bigger stem hole you well need to make a bushing to fit the xs400 stem.
Weld it back up.
Much better than cutting up a frame.
Leo

 

[dO-bOy]

I grew up in coquitlam! Centennial alumni!

 

[bentwrench]

Bentwrench described one way to get a different frok on your bike, another is to get the fork you want, remove the stem, from the xs400 lower tree and the stem from the new tree and put the xs400 stem in the new tree. This rquires grinding out the welds and pressing them out. If the new tree has a bigger stem hole you well need to make a bushing to fit the xs400 stem.
Weld it back up.
Much better than cutting up a frame.
Leo

Thanks for reminding me. This is another way (there's always another way), but I just don't have a good step by step link for that method.

 

[frwinks]

hey Jimbo, thought I'd throw these here so more people in your sit can view it..
Your 20mm axle has a step which will center the wheel in the forks, the other side gets measured once the wheel is in and a spacer needs to be made. Mine is steel, you could make it out of alum.
I'll get the part numbers on the bearings for you on the weekend....

 

[Nuno]

I fitted a Ducati fork (UPD of course), 320mm disc and brembo caliper on the original wheel of a '82 DOHC.
All you need is new bearings (wheel and stem) and a lathe for 2 spacers.

 

[bentwrench]

What year and model of Duc?

Of course, putting a Ducati front end onto a Yamaha 400 is a little like putting a 2 carat diamond on your pet pig... seems like a lot of bling for the bike...

 

[Nuno]

What year and model of Duc?

Of course, putting a Ducati front end onto a Yamaha 400 is a little like putting a 2 carat diamond on your pet pig... seems like a lot of bling for the bike...

the fork is from a '96 Monster 600, triples are from a '02 SuperSport. What really matters to me are the clamps, now I can use any fork of that size (probably going to use a Showa from the Monster 900).
As for the 2 carat matter......My bike has nothing standard...doesn't matter if it has 40hp or 80hp...I still want to be able to take a decent corner and to stop properly. The frame is standard but hey...have you seen a '99 Hornet frame? Same concept, thinner, ugly...and 100hp.
Don't get me wrong...it's no race bike at all, but 200€ of fork and triple clamp are no big deal. (plus I wanted the 320mm disc and it becomes plug-in once the fork is in place)

 

[bentwrench]

Might be geography too. I'm not sure I could find a Monster front end for anywhere near $300 CDN (rough exchange calculation...) Glad the stem fits, though!