XJ rims on Ducati Forks?

[Fox]

Howdy Gents,

Starting to do some research for my '82 XJ550 so I can be parts watching. I'd like to convert the front end to a dual disc instead of the single on there now. I know a lot of guys just do a fork swap with a GXXR or something, but I was looking at using a Ducati Monster front end. Like the look better, but might have to look for something else considering availability. Open to suggestions there.

What I'm really wanting to do is keep my XJ rim and try to mount up another disc on the other side of it. No idea if this is possible or not, just prefer the XJ rims. It's all just in idea form right now, would love to have yall's help turning it into reality.

 

[DesmoBro]

....this is where it can get expensive....

http://www.ducati.ms/forums/129-parts-accessories/135621-fs-monster-fork-marzocchi-696-796-1100-a.html

I personally havn't ever found just the tubes for under $300...although somtimes you can get lucky and score an entire front end (triples,forks, calipers, wheel, tire, sometimes levers and cables too!)

First thing i'd do is see if your axle is even close to fitting in the clamps

 

[Tim]

Swapping out front ends and using your stock wheel can start getting expensive quickly unless you're a machinist.

I'm running a GSXR front end on my SR500, with Honda CB hubs, dirt-track racing rims, an FZR1000 rotor and 6 pot Tokico caliper. Was an interesting exercise to make it all work together. A machinist friend turned a new axle and spacers for it and a spacer for the rotor to meet the caliper.

Swivel is right. Chances are you could put a larger rotor (like the FZR1000 for example, or perhaps a smaller one - 320mm is pretty big) on the wheel, a better caliper and only have to deal with an adapter plate to mount the caliper to your fork, and spacers to align the caliper and rotor.

Swapping out the forks on top of that just adds more drama and expense. I'm only doing it because it's one of 5 bikes in my garage and I felt like it.

Really what you want to think about is the original issue of why do you want dual disks? Is it the extra braking power? Is it the appearance? I run a single disk on my 1975 BMW R75 and it's plenty of power when properly sorted. Good rotors, pads, brake lines and bled properly and you have all the stopping power you need.

 

[crazypj]

Almost anything is possible if you have the equipment, ability and (or) big wallet
I'm going to put the blue special edition GSX 750 R forks on my 360 brobber. (invented a new word for brat/bob ;D )
It is quite a lot of work and a lot of material.
Modifying steering stem to use stock Honda bearings (easier and cheaper in the long run than 'special' bearings)
I'm using 360 hub/wheel, not sure about rotor/caliper yet?
I'm also doing a second one for Neevo (working on a bike 8~12,000 miles away is a bit of a challenge )
He's using 360 hub, CBR rotors and calipers which need spacing out 30mm (15mm each side)
I've designed a pretty slick set of adapters to fit 15mm axle into 32mm fork ends, going to be real rigid set up. (and look good doing it 8) )
It isn't going to be cheap or easy, particularly if you have to pay for materials and machining
I will have a spare pair of caliper adapters to fit CBR rotors to CB350 twin, CB350F, CB360, 400f hub/forks as the gixxer forks are a lot wider so need thicker spacers : (you'll have to work out your own caliper mountings)

 

[Fox]

I'm gonna respond to each one of you because this is all good information and I want to make sure I understand/give my thoughts on all of it.

I'm ok with spending some money to get the set-up that I want. I know I'm not signing up for the easiest mods available, but now that my CL is done (almost) and I'm going to have a garage next year, I'd like to try something a bit more... challenging.

Usually I'll take you at your word Swiv, but I'd like to see some sort of data to back up the fact that Ducati forks are low-quality. That being said, I'm not ruling out GSXR/R1 shocks. I actually had the idea to do a V-formation rear shock pattern a la R1s. We can talk about that later though. I should explain that my motivation for this build isn't performance oriented. About 50% looks and 50% because I feel like it. I chose Ducati because I like the looks, I like to be different, and I like the idea of having a Frankenducati bike. Maybe I'm being too vain, but I don't care. I just wanna have some fun, but I don't necessarily have to play with Ducati! BTW, can you tell me more on internal spacers for the stock forks? Might be interested in that for another bike.

As mentioned earlier, I'm of a similar emotion, because "I feel like it". Yes, it will be expensive, but I'm a single guy living on my own with little exspenses. I can either spend my money on shit that doesn't matter, or I can spend it on something I love and I love doing (read: motorcycles). I'm not completely turned off to the idea of a single disc, I just love seeing a vintage bike with dual discs. Really aggressive and eye grabbing. Something I want.

If I want to keep my my XJ rim, do I have to find another bike that has the same hub size and and axle diameter? I'm just not sure what I need to be looking for. So many measurements that that it's hard to keep them all straight. What I could find is...
Front Axle Diameter
15mm
Steering Stem Bearing Sizes
Upper: 25 x 48 x 13
Lower: 30 x 48 x 13
Fork Tube Diameter
36 (mm?)
Found this site for sourcing bearings for a fork/steering stem change.
http://www.allballsracing.com/index.php/forkconvertion

Correct me if I’m wrong, but if I want to hold onto my rim my perception of it is this,
New forks will require spacers for my axle and a spacer for my hub to make the discs meet with the calipers on the new forks. That’s the rim. Then for my steering stem, I’m going to need new bearings and might have to modify the frame to make the steering stops work effectively. Yes? Am I missing something?

I was wondering who was going to be the one to say the “anything is possible" line.
Could I contract you to do this machining for me? It probably won't be for a little while, but I’d rather do business with someone who knows my goal/works on bikes. Plus, I just like you better than any other machinists I know.
Btw, could those spare adapters fit a CL360 if I swapped forks with CB disc forks?

I’ll be going out of town for a week tomorrow morning and I won’t have my computer/internet access, so if I don’t get back to you guys by tomorrow, we’ll pick up a week from now.

 

[Tim]

The stem on the Ducati front end might not be the right length. All Balls will tell you the bearings for top and bottom, but they don't account for the length of the stem which is critical. Chances are you won't know till you've got one in hand, unless you can find someone to measure the Ducati stem for you. The top bearing needs to sit in the right spot and the lock nuts need to cinch down on things.

You'll need a whole new axle most likely. This can get tricky, as the axle needs to be fat on both ends to mate with the forks and skinny in the middle for your wheel bearings. You can / should swap out the wheel bearings to get the biggest ID possible, but it's still not going to be enough to match the Ducati axle. A machinist can make the axle / spacers etc. for you. Best bet is you take the forks and wheel, caliper and rotor to a competent machinist who understands motorcycles and tell them to make it fit, and hand your wallet to them. That's what I did.

 

[Fox]

I don't want a bike LIKE a Ducati Monster. If I did I would have saved my self a load of trouble and just bought one. I want Ducati parts on a vintage motorcycle. I've never seen anyone do it, so I thought "Why not try?" I appreciate you trying to persuade me to an easier and probably better option, but I'm going to persist with my goal of having dual discs at least until I can figure out how much its gonna cost.

It's not so much performance that I'm looking for, as I want to do something new (New for me at least). If I can fit some Ducati forks or some R1 forks that aren't the best things in the whole world, then that's ok. I don't need to be the tip top quality stuff (and pretty much anything pre-2000 will be an upgrade from stock front end). I'm doing this because I think it will look cool, and I want to. If I can get a performance upgrade from it then thats freakin' awesome, but I'm not gonna feel jipped if It doesn't handle like an Aprilla when I'm done. It's a 30 year old bike, lets not forget that.

A wise man said never own more motorcycles than you can ride at once.
Says the man with a 20-bike garage...

You'll need a whole new axle most likely. This can get tricky, as the axle needs to be fat on both ends to mate with the forks and skinny in the middle for your wheel bearings. You can / should swap out the wheel bearings to get the biggest ID possible, but it's still not going to be enough to match the Ducati axle. A machinist can make the axle / spacers etc. for you. Best bet is you take the forks and wheel, caliper and rotor to a competent machinist who understands motorcycles and tell them to make it fit, and hand your wallet to them. That's what I did.

Yeah, I read that. I just figured it would be a good place to start from. Gonna reach out and look for others that have swapped front ends on XJs. Might give AllBalls a call, see if they can help me out. How do I verify that the bearing is going to sit in the right spot and that the lock nut is going to cinch down on the right spot?

Damn. That'll be expensive. Can you explain what you mean by swapping out the wheel bearings to get the biggest ID(Not sure what that stands for)? Working on finding compatible front end swaps so we can start talking specifics and calculating geometry (see how I roped you guys into helping me with that by using 'we') Haha. As far as machining, I'm hoping PJ will be able to work with me a bit. We'll see...

Swiv,
As far as all those measurements go. That's what I'm going for, but I don't think it's gonna take me two years. It's just a CAD drawing. I can hire out a PhD Georgia Tech grad down the road for a week and he can draw me up something like that. I want to go that in depth on this build though. I don't want this to be badly engineered, so I'll be counting on the fine members of DTT to walk along with me, including you Swiv.

 

[Fox]

Used Sherm's method of sourcing donor bikes for front end swaps. Was wondering if I could get one of you guys to check my work essentially. Came back with the results that and R6 front end up to 2007 would fit.

Found this one on eBay, Link Am I right?

Would I be able to use my XJ steering stem with the R6 front end if the steering stem didn't fit or could that be potentially hazardous?

 

[crazypj]

PM me about spacers, if it's 4 bolt hub, they fit
Just get some Gixxer forks and Ducati stickers
Forks, brakes and all the fittings will probably run at around $650.00+ by the time it's all done (eBay forks around ~$299.00)

 

[Fox]

PM me about spacers, if it's 4 bolt hub, they fit
Just get some Gixxer forks and Ducati stickers
Forks, brakes and all the fittings will probably run at around $650.00+ by the time it's all done (eBay forks around ~$299.00)

Went browsing for some GSXR forks. Looks good as far as price goes. I'm just reluctant to do as everyone has done and use those forks. Maybe I shouldn't be so industrious on my first front end swap. Anyways, I'm not sure what years to be looking at for the Gixxer. Using Sherm's method for fork swaps (linked above) I should be able to have front end swaps from: GSXR1100 86-98, GSX-R400 (Euro) 90-94, GSX-R600 92-93, GSXR750 86-95. This is because my XJ has the same size steering stem as a '98 XJ 600(Readhiocaferacers.com) and those Gixxer front ends fit on the XJ600, so they must fit on mine also. Seems like a weird way to go about it, so can someone correct me if I'm wrong? I thought I used the method prescribed to me.

Theses quite a few bikes I can get front ends from if I can actually get the same front ends as the XJ. Here's the full list

 

[crazypj]

GSXR used different diameter steering stems on later models.
The top bearings are much larger on some so are more difficult to fit.
Anything after 1995 should have cartridge forks in USD, the conventional style GSXR forks were also cartridge and 41mm dia up to around 2002

 

[hillsy]

This gives you some idea on how geo is measured on a sport bike.....

It's from the www.DBBP.com/ site.

I'd build a bike just like the the quality of this DBBP design,if I had a lazy USD300K to do it right.....and two spare years to do nothing else but build.....

There's nothing right about that ridiculous tyre size combination. Chopper builders trying to build a sports bike. They have no idea.

 

[Fox]

I've been thinking about what forks I want to go with, and was wondering, couldn't I use any front end set up that had the same bearing diameter as my XJ? If the steering stem ends up being too small then couldn't I just take the steering stem from my XJ and press it onto the new, lower triple tree? That would solve the problem of having a steering stem that is too long and I could use any of the bikes recommended on AllBalls.com. Anyone see a problem with this?

Sent from Tapatalk and shit.

 

[damarble]

Damn. That'll be expensive. Can you explain what you mean by swapping out the wheel bearings to get the biggest ID(Not sure what that stands for)? Working on finding compatible front end swaps so we can start talking specifics and calculating geometry (see how I roped you guys into helping me with that by using 'we') Haha. As far as machining, I'm hoping PJ will be able to work with me a bit. We'll see...

What he means is say your XJ bearings are, say, 32mm outside and 16mm, but the Ducati axle is say 20mm, try to find a 32mm OD/20mm ID (inside diameter) bearing.

I think I have a good shot at finding bearings to avoid a custom axle on mine. My KZ axle is 19mm and the ZX axle is about 22mm so there's not much to make up.

 

[crazypj]

It's highly unlikely steering stem would swap into a modern sport bike yoke although it is a possibility?
You may find a YZF, R1, R6, etc front end could be easier swap than Gixxer?

 

[Fox]

Thanks for the explanation. It all makes sense now...

PJ,
Yeah, it is pretty unlikely, but if it did work that'd be awesome. I'm gonna try and call around to a few shops when I get back to see if I can get a solid answer on what front end will fit best.

Yeap. I'm looking at those front ends too. I really like the R6. We'll see when I get back. See yall then.

 

[crazypj]

It's even more doubtful any local shop will have a clue
Unless they build oddball stuff it's quicker and cheaper to get something out of catalog or use stock parts (time IS money in business)
You'll have to grind welds off XJ yoke to get stem out

 

[hillsy]

The way to measure geometry is right and the rake/trail/wheelbase stuff is spot on,look at it closely.It's not a blue print for the XJ,it's just to show some design stuff and stimulate his imagination....

So you copy a decent geometry set-up and stick the most ridiculous tyre combination on it??

Like I said - chopper builders having a crack at sportsbikes. Clueless.

Back to the XJ front end swap question - generally speaking same make swaps are "easist", so maybe look at R1/R6 front ends (although we're talking generations apart here, so it may not matter). Also you will probably run into clearance issues with the wheel spokes if you try to use the donor forks' caliper, so you might need to use the XJ caliper and machine up an adapter to mate it.

You're in custom fabrication territory here so you'll just have to suck it and see

 

[Fox]

It's even more doubtful any local shop will have a clue

Yeah, I can't remember why I said I was going to call a local shop. Delusional I'm sure.

Back to the XJ front end swap question - generally speaking same make swaps are "easist", so maybe look at R1/R6 front ends (although we're talking generations apart here, so it may not matter). Also you will probably run into clearance issues with the wheel spokes if you try to use the donor forks' caliper, so you might need to use the XJ caliper and machine up an adapter to mate it.

You're in custom fabrication territory here so you'll just have to suck it and see

Yeah, for this swap I'm going to stick with Yamaha parts. This is my first venture into Custom Fab territory, so I'm sorta feeling it out as a I go. Yeah, Definitely noticed that the clearance issue with the new forks. I might decide to keep the R6 rims. I wouldn't mind much, just so long as the front and back matched.

I'd fit a smaller RDLC 18"front wheel and lower the stock forks with internal spacers and with a XJ550 18" matching rear...But....

The non-USD R6 front end option may be achievable if the matching R6 rear wheel will squeeze in the stock XJ swingarm,even if it needs a slightly smaller tire than the R6 OEM tire to do it(Like the next size down).....

The RDLC rim is becoming a larger and larger possibility for me. Same rims but dual disc. I just wish it was USD. Not for performance or anything, but because I like the way it looks on vintage bikes. If I did go RDLC, it would make the monoshock process a whole lot easier since I could use one of the their swingarm's. Hmm. Very very tempting. The question is how bad do I want to have USD forks. I like the non-USD R6 forks idea a lot actually. Are you thinking just a fork swap or a whole front end?

 

[hillsy]

If you're looking for a rear rim to match an R6 front look at FZR400 or GS500 twin. You'll need to convert to rear disc, but these guys will be in the ballpark as far as chain line and tyre size goes.