Fitting modern front in on a 1977 xs400D

skervey35

skervey35

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Hey guys i am the new owner of a 1977 xs 400 the bike isn't running now but its close! But it wont be ready to hit the road for a good while. The front brakes are shot both the caliper and master cylinder. The forks are going to need rebuilding as well so i thought i would do like some other people have done and fit a front end off a new sports bike to the XS. Like this guy did in his XS750 -
yamaha-xs-750-classified-moto_1.jpg
So i would have the modern shock and breaks and it would be easy to find a front end off a wrecked bike but i would swap triple tree and all ill have to find new head light brackets and a way to hook up a the tack. and speedo. So i was just wanting to see it anyone knew of a front end that would mock up. i think the only thing that would really matter (correct me if om wrong) is the head set size??? I have no idea where to start...
 
Might try looking over at xs650.com, they have some great information there that will help you. And I definitely don't mean make a thread like this over there. Search, it works.
 
Iv been on XS650 and looked over the huge post of fork sizes but i was wanting to know more about the head set size not the diameter of the fork tubs
 
skervey35 said:
Iv been on XS650 and looked over the huge post of fork sizes but i was wanting to know more about the head set size not the diameter of the fork tubs
Click to expand...

Wrong post, there is a great post about specifically the neck tube modification required and all sorts of neck tube information.
 
Hey thanks for all the info! I was going to try and use the stock fork for a while but the break was bad so i tried to rebuild it but its rusted up bad. So im going to need a new caliper, so instead i may just put a new fork on the bike now. Been talking to some guys on ebay there is a whole font end off a Aprilia RS125 but its in Ireland so im trying to get a price for the shipping. But im also talking to a seller to see if he can find me a front end with 50mm fork tubes so i can slide them into the Aprilia RS125 triple tree. Hopping he can find one for cheaper than shipping that one from Ireland. But im in no big rush i wont be able to get much work done for then next few months anyway.
 
I have an XS650, but people have made brackets pretty easily to fit modern sportbike brakes on. I am actually working on putting an R1 caliper on my stock rotors and forks.
 
Plz tell me more! haha i am only 20 so i don't have a grate big shop where i can build my own parts. In saying that my room mate is studying engineering and i know my way around CAD programs and he my be able to get access to a CNC and cut me out a bracket but i have no idea where to start. I guess ill see what rotors fit my stock wheel and find a caliper for that rotor. But that doesn't sound like a bad idea. I will have to rebuild my fork, its in bad shape...
 
You are overthinking it. Use the stock replacement rotors like anyone with an XS400 would use. Then you adapt a caliper to your fork leg caliper mounts. Pretty simple actually. I am sure an R1/R6/FZ1/FZ6 rotor would work as your XS400 is probably pretty similar to an XS650. Here is the thread on the big boy site: http://www.xs650.com/forum/showthread.php?t=197
 
Iv seen the stock replacement rotors but i would need to make a bracket to fit another caliper to the stock fork right? (Amusing i buy a caliper form a R1 or something like that)? But it seems just as cost effective (seeing as i would have to rebuild the forks that are on my xs now and buy the new rotors and buy calipers to fit it all) to buy the inverted fork off a Aprilia RS125 then i would get a modern fork like i want and modern brakes and calipers that were made to fit the forks and rotors. idk just seems to be a easy way to get the look i want along with fixing my brakes. The only thing i would need to change is a new headlight and i will have to get lower bearing for the Aprilia and it takes a 48x25x15 bearing to do the swap.
 
I don't know how much it is to rebuild forks, but I would be guessing it would just be a set of seals and fork oil which is cheap. If you current rotor is good, you don't need a new one, so that is free, bracket is a piece of 12mm thick aluminum which would be cheap, just need to cut it and the caliper costs $40 shipped on ebay all day. I think what it really comes down to is you WANTING a sportbike front end. If that is what you want, go for it. I thought about doing the same, but couldn't find an affordable front end.
 
Ya i really want one but like you said it all comes down to cost. And as its looking now that would drain my pocket.. and the bike doesn't even run yet! So i guess i will just have to price things out. Im almost to the point of taking the bike to someone to get it running because my lacking experiences with motorcycles motors and carbs. Also i cant get the bike to shift threw all 6 gears so im afraid im going to run into transmission problems. There is enough room in my budget to replace the motor and transmission if the one i have is no good. So i think im going to focuses on getting her running and if i have the funds to get a modern fork then i will.
 
Old motorcycles are gonna cost you some cash. So if you aren't prepared to drop some coin, I would step back and reevaluate your situation. The good thing about these old bikes is the ability for anyone with basic mechanical experience to bust into them and get them running. You need a friend who can show you. Or some courage. Grab a camera or video recorder and start taking the carbs apart. Pretty hard to mess it up unless you lose something, which the only thing I have run into losing is the ball bearing in the choke rod on my bike. Good luck with whatever you do.
 
First off, any modern sport bike fork conversion won't be cheap. You might have a good deal on a set of RS125 forks, but shipping from Ireland will be pricey. Do they have calipers? What wheel are you going to use? If you use the stock wheel, what rotors? What about spacers? Clip ons? You'll need a bigger master cylinder, so new levers.
I'm not trying to discourage you, but let you know that it's not just something you can easily do. It's def possible, but it's going to take at least $300-$400 (unless you can find an amazing deal). So yeah, rebuilding the stock fork would be cheaper. There's also the option of doing the double disc conversion which uses the fork leg and caliper from an XS750 (I think).
Also, as I stated in my thread, the CBR954 triple should work (and is available in the US) and that would give you the flexibility to work with Gixxer/CBR/Ninja/R6 fork tubes (50mm tubes, that is) and parts. I'm using Gixxer 600 tubes, CBR954 triples, Ninja 636 calipers and clipons, and FZR600 rotors (more than likely) on the stock 18" mag. I'm just taking my time amassing parts.

Hey Joel, what part of town are you from?
 
Thanks Man ya iv been taking a ton of pic iv rebuilt one carb are cleaned both of them and been trying to kill all the rust i can find but as for getting the bike running there are so many little things that need to be perfect to get the bike to start and the bike hasn't ran in X amount of years so its not going to just start right up. I can read about how to do it all day but reading and doing are two different things haha as far as cash goes im ready to spend some cash but i want to spend it in the right places and im not able to work all the time since im away at school but ill finish the bike on day! Im also hoping to do a build thread when i get back up to school so i can have your guys input on how im doing.
 

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