XS front end swap

[Rev D]

I am the proud new owner of a 79 xs650 and I'm looking to dig into this one pretty quick.
I've been taking stock of what I need and have been poking around a bit to see what some front end options are. Reason being that I need a new MC and caliper, and I think the front seals are toast too. I've been doing some looking around and it seems that the forks that come on the front of these bikes aren't that great performace wise (and the brakes apparently are a little weak) and I like the look of some sport bike inverted front ends on some bobs and chops I've seen.

So here's the million dollar question. Anyone done that before?

I know I need a yoke spindle that is as long or longer than my head stock, but is there anything stoping me from getting a front end from say, a gsxr, and having my spindle pressed into the trees? That would seem to be the plainest solution to keep my bearing sizes the same and not having to machine any bearing cups or anything.

Or am I just crazy/ignorant?

I would really value any experience or advide you guys could give me.

Thanks!

 

[Teebs]

PM Sky (Yamaha Chop) about it. He's done a chop with a sport bike front end (a gixxer I think) and currently doing an XS650 sport bike with a modern front end. Here's a link to his chop: Sky's Chop Maybe he would be willing to post a thread about his conversion. I'd be interested in the particulars as well. Oh, and welcome to the nuthouse!

EDIT: Keep in mind that most sport bike trees don't use risers for the handlebars, so you would either have to look into some type of modification unless you're going to run clip-ons.

 

[Rev D]

Thankas a lot!
And I'm not sure about bars yet, clip ons look sweet and it would keep the bike looking low, but I want to go one looooong rides so we'll see, it might work (I'm 6'2", I might be able to reach fine).

 

[Rev D]

OKay, talk to Yama_chop and he did his swap with an ingenious type of drill and slug method.

Anyone else have any techniques or advice I could consider?

 

[Lunatic]

Me and a buddy used Kawasaki ZX-7 fronts on our XS's.

The process was something like this:

- Carefully cut XS neck stem out of the XS lower triple.
- Cut ZX-7 neck stem flush with the ZX-7 lower triple. It becomes a steel bushing in the aluminum lower triple.
- Machine bottom of XS neck stem and the inside of the remains of the ZX-7 neck stem so they press fit together tightly.
- Fit the XS neck stem into the ZX-7 triple and tack weld the stem to the bushing at the bottom for safety.
- Bolt it all up to the frame.
- Scare the bejeezus out of yourself at the first fast corner. (but she stops on a dime! )

We had the work done at a local machine shop, cost was about $100.

Some more pics

 

[Ironsled77]

thats a serious front end like the car in the back round. yours or a car show?

 

[Lunatic]

Unfortunately it's not my truck

It's an awesome 50's Dodge cab on a custom frame, running an incredibly rare 241 Hemi.

The owner is a member of the Bottom Feeders car club here in Toronto.

 

[Teebs]

Bad ass truck! Sweet bikes! Great fork conversions. Up until this morning I was going to put a Harley wide glide on mine, but I've decided to build my own leafer instead.

"It's semi-ev-il. It's quasi-ev-il. It's the margarine of ev-il. It's the Diet Coke of ev-il. Just one calorie, not evil enough..."

 

[Rev D]

Thanks for the info Lunatic.

My only fear on this whole endeavor is safety, since I really don't know too much about machining. I'm looking for the strongest way to do it and this seems to be a good suggestion.

Presumabley then all I need is a front end with a neck stem that is thicker than the xs one?

And by scare yourself on the first coner... becuase the handling was much worse or much better?

Thanks

 

[inxs]

"It's semi-ev-il. It's quasi-ev-il. It's the margarine of ev-il. It's the Diet Coke of ev-il. Just one calorie, not evil enough..."

- evil is live dyslexia

 

[Lunatic]

Thanks for the info Lunatic.

My only fear on this whole endeavor is safety, since I really don't know too much about machining. I'm looking for the strongest way to do it and this seems to be a good suggestion.

Presumabley then all I need is a front end with a neck stem that is thicker than the xs one?

And by scare yourself on the first coner... becuase the handling was much worse or much better?

Thanks

Strength is not a worry at all with the way ours are built.

For a front end, obviously a Kawi ZX-7 works nicely, but you should be able to adapt pretty much anything with the help of a decent machine shop. There are definitely people who have done similar swaps with other front ends.

It's scary because it's different. I'm used to a Kawi Z750s (my daily commuter/touring/sport bike) and the handling of a lowered XS is certainly not up to that level. As long as I don't try to push it like I do the Z then it's not scary, but if you go too hard into a corner it's a little hairy. Mostly it just takes getting used to, I've only just really started riding my XS since we built it over the winter. I never rode it when it was stock so I can't really compare how it handles now to stock.

 

[Sundie]

I never rode it when it was stock so I can't really compare how it handles now to stock.

<cough>youdon'thavetostopinthehairpin</cough>

 

[Lunatic]

<cough>youdon'thavetostopinthehairpin</cough>

Maybe you shouldn't follow so close?

 

[Teebs]

It's scary because it's different. I'm used to a Kawi Z750s (my daily commuter/touring/sport bike) and the handling of a lowered XS is certainly not up to that level. As long as I don't try to push it like I do the Z then it's not scary, but if you go too hard into a corner it's a little hairy. Mostly it just takes getting used to, I've only just really started riding my XS since we built it over the winter. I never rode it when it was stock so I can't really compare how it handles now to stock.

Lunatic, did you measure the trail with your new front end?

Rev D, a way to convert to the shorter, beefier forks and control the trail to keep it within the optimal range (2-4") is to have someone machine a set of raked trees using the stock stem. It might be spendy but worth it to have the new front end and still have a bike that handles properly. Raking the neck is another option.

There isn't any safety issue where the stock stem is concerned. The forks are what make it flex-y. Stem length is more the issue.

 

[Lunatic]

No, we didn't measure the trail, just bolted it on and went riding.

In truth it doesn't handle badly, it's just a big adjustment going from a tall, high center of mass sport touring style bike to really low, short, stiffly sprung bar hopper. I love it for cruising around town, but if I'm hunting for twisty back roads I will take my Z instead.

Sundie is just giving me hell for going too slow around an uphill 180 degree switchback the first time I was really out on the bike.

 

[Teebs]

...but if I'm hunting for twisty back roads I will take my Z instead.

Thanks, Captain Obvious!

That's cool. With a change in forks, I was really more curious to know how much of a change it made than anything. Just by looking at it, it's obvious the trail is reduced, but not by enough to make it unsafe. It seems it would take some getting used to though.

They also look great. Nice conversion.

 

[Lunatic]

Thanks, Captain Obvious!

That's cool. With a change in forks, I was really more curious to know how much of a change it made than anything. Just by looking at it, it's obvious the trail is reduced, but not by enough to make it unsafe. It seems it would take some getting used to though.

They also look great. Nice conversion.

I think the biggest change other than riding position and brakes is the lack of dive in the front end under braking. I haven't played with the adjustments on the ZX-7 forks but they are obviously miles stiffer than stock XS forks.

The conversion was done as much for looks as anything so there almost certainly are other inverted fork options out there that would work and may be the same length as the XS forks so the geometry wouldn't change.

Another option that would pricier but not as bad as many would think would be to have custom triples made to match both a specific set of forks and the XS neck stem. I've seen a couple of posts on other boards where someone has milled out some simple triples from aluminum to fit a specific set of forks and neck.


One thing I forgot to mention in my original post was the steering stop. We cut off the original stop and welded on a section of square tubing to act as a stop that would work with the ZX-7 triples. Depending on the specific triples used you may or may not be able to do something similar. We did see some differences even in the different years of ZX-7 front ends we used.

 

[Teebs]

Another option that would pricier but not as bad as many would think would be to have custom triples made to match both a specific set of forks and the XS neck stem. I've seen a couple of posts on other boards where someone has milled out some simple triples from aluminum to fit a specific set of forks and neck.

Hey! That's what I said!

 

[Lunatic]

Hey! That's what I said!

LOL, true, but I wasn't thinking about raked trees, more about finding the right length forks and making them work instead of making it more complicated, I hate math.

 

[73novaguy]

Nother option for these bikes is the FZR forks and trees. They are not USD forks but a very nice change, especially with a top aluminum clamp. You'll have to drill for risers though if you want handlebars.