Another FZ1 swingarm, but a little different too.....

[great white]

With my FJ12 laid up for long term work, I'm looking at doing a 1st gen FZ1 swingarm installation. I just put some Kerkers on it and there;s an FZr750 front wheel and FZR1000 rear wheel waiting in the rafters. So if I'm going to do the FZ1, now seems the time.

But here's the thing: I don't want to add that 1-1.5" to the wheelbase. For some reason, I can really see the wheel pushed back on all the swap pictures I've seen and it's like a sharp stick in the eye to me.

I've had the swingarm sitting around for a year or two now, having ran across one for 50 bucks. Axle, pivot, brake stay and bracket, etc. I just had to grab it at that price.

I'm also not going to be "heartbroken" If I end up sticking with the stock FJ12 arm.

So with that in mind, I'm going to build a steel jig to hold the FZ1 arm and then cut the ends off it. Then I'll section out enough length to match the FJ12 arm and weld it back together.

Once that's done, it's back to the relatively easy task of milling off enough of the pivot to fit the FJ12 frame.

If I end up tossing it into the smelting furnace to make ingots, no big.

So it's worth a try. Should be interesting, I'll try and post some pics as I go along.

[aviationfred]

Contact Joe Berk (Country Joe) about the chain adjustment bushings that he had designed for the FZ1 swing arm swap. The make life much easier.

The silver spacer between the swing arm and caliper hanger in the photo. Installed from the outside, it is also used for the chain adjustment.

[Troyskie]

While we're on swingarms, who's done a JMC IOM TT swap?

[great white]

Well.

Built the jig and clamped the fz1 swingarm down.

Then started taking measurements.

I had planned to take 1-2" out of the rear straight portion. But on measuring, turns out there is no extra to cut out. I need a minimum of 13" to the crossbrace from the axle center point to fit the tire. Taking 1.5" out of the straight part of the arms would put the tire solidly into the cross brace by at least an inch (and thats with tha adjusters full readward). So that's just not a workable solution.

Further measuring shows approx 2" more from the arm pivot to the front edge of the cross brace. Same with the measurement from the linkage pivot lower mount to the arm pivot centerline. So it seems the FZ1 "extra" length (compared to the FJ) is all in the forward section.

Problem is: that part of the swingarm tapers in on the sides AND at the top and bottom. Just taking a slice out there is not an option either. Not to mention, I seem to recall the FZ1 swingarm is an extrusion with internal ribs/webs. No way to weld those internal structures back together once cut and that will compromise the rigidity of the arm, which is the reason for installing it in the first place.

So it looks like my only option is to cut the arm where it connects to the forward pivot tube and move the whole pivot tube back the needed 1.5-2", then weld it back together. It would probably mean having to cut and re-taper the upper and lower sections to meet the upper and lower part of the pivot tube as well. The taper on the outer portions wouldn't be much of a problem, they would just move out a touch on the pivot tube from moving the tube back Providing the frame won't interfere with the slightly wider weld points.

Have to sit and think about this one for a bit now. Turns out chopping that 1-5-2" is going to be much more work than I had planned for and if I do it wrong, I might run the rigidity and structure of the arm...

[great white]

Contact Joe Berk (Country Joe) about the chain adjustment bushings that he had designed for the FZ1 swing arm swap. The make life much easier.

The silver spacer between the swing arm and caliper hanger in the photo. Installed from the outside, it is also used for the chain adjustment.

Thanks, but thats a 20 min job (tops) on the lathe for me. No sense buying something I can make myself from leftover bits of Al...

[great white]

While waiting for the paint on my intermediate pipes to dry, I pulled the swingarm and did a little layout work:



I lined up the suspension linkage mount and made the measurements off there as the reference point. Since the linkage is progressive, i want to keep the ratios the same. Changing any of the mounting geometry changes the rates. May be a problem, may not. I want it to be the same so I'm not introducing an unknown variable into the swap. Same with wheelbase and height. Stock FJ wotks fine for me, so I need to get it to that point and then I can change whatever aspects I want from there.

So, there's 1.75" that has to come out of the front ahead of the cross brace (swingarm pivot moves back). There's also 1/2" that needs to come off the rear to move the axle to the same forward postion. The FZ arm has much kess range of adjustment than the FJ, so I need to get it right the first time.

Problem is that makes the tire clearance to the cross bar 12.5", which is pretty damned close when the tire is installed. I'll have to do some more mockup to check things out, but it's beginning to look like a heck of a lot of re-working to make it fit exactly like the orginal FJ swingarm.

[ribbert]

Have to sit and think about this one for a bit now. Turns out chopping that 1-5-2" is going to be much more work than I had planned for and if I do it wrong, I might run the rigidity and structure of the arm...

I have been following this and have to ask the question, why? With the obstacles it has presented and the amount of work to get it done, what benefits do you expect from the job and is your riding style such that you will even notice?

It just seems like way more work than the end result justifies.

Noel

[Pat Conlon]

Yes, I'm with Noel on this one.

Fred, in your picture showing the index marks with the chain adjusted, Is that with a 110 link chain?

Or do you have to run a longer chain with the FZ swinger?

My point is, if Fred is indeed using a 110 link chain (oem length) that picture shows Fred's chain adjusted in good relation with the FZ swingers index marks.

I see no need to shorten the swinger.

[great white]

Sometimes, it's more about doing the project than the end result. Occstionslly, I'm that guy that does it because he can and thats reason enough.

I may end up just bracing the FJ arm and calling it a day.

Then, when I feel like it, chop up the FZ1 and see what I get. I have nearly no money in it and if it ends up melted down for casting aluminum, I'm just as ok with that.

Everything I've read on the FZ1 arm change requires a longer length chain. My sprockets and chain (110L) literally just csn out of thier boxes today so I have absolutely no inclination to buy another chain.

Then there's  the longer wheelbase (just over 2") and the accompanying visual "off-ness" of the wheel shifted back that 2". May not bother most guys, but I see it and it bugs the heck out of me.  The FJ isn't exactly a shirt wheelbase to start with and another 2" is only going to make it more... well, lets just call it more "stable"....

Chopping up the FZ1 arm is a fun little aluminum welding project for me either way.

[Country Joe]

Great White,
Just something else you need to consider about the FZ1 swingarm swap is the difference in location of the dog bone attachment point of the FZ1 and the FJ swingarms.  The mounting point on the FZ1 swingarm is too far rearward compared to the FJ. You can make longer dog bones and bolt it all together, but I found that the ride and handling was far less than optimal. I cut off the lug on the bottom of the FZ swingarm, had a block machined to receive the FJ needle bearings and had it welded to the front of the swingarm cross member. It restored the suspension linkage geometry to where I ended up using the original 3XW dogbones and that left me with 5/8" of clearance under the rear tire while on the center stand. I tried the unmodified FZ1 swingarm for a couple of months and never could get it to ride well at all, even with the RPM shock. If you don't like the extra length of the FZ1 swingarm,  you really would be better off to just build a brace for the FJ swingarm and call it a day.

Joe

[aviationfred]

Yes, I'm with Noel on this one.

Fred, in your picture showing the index marks with the chain adjusted, Is that with a 110 link chain?

Or do you have to run a longer chain with the FZ swinger?

My point is, if Fred is indeed using a 110 link chain (oem length) that picture shows Fred's chain adjusted in good relation with the FZ swingers index marks.

I see no need to shorten the swinger.

Good eye Pat,

When I did the swap, I purchased a 120 link chain and cut it down to about 116 links if I remember correctly.


Fred

[Pat Conlon]

Well alrighty then, a 114 link chain, that mesh's with GWN's measurements.

Interesting post from Joe on the different locations on the linkage points.
I don't recall anyone in the past noticing that difference, or correcting it like Joe did.

Got any photos Joe?  

Start a new thread so we can return this one back to GWN's mod.

[great white]

Great White,
Just something else you need to consider about the FZ1 swingarm swap is the difference in location of the dog bone attachment point of the FZ1 and the FJ swingarms.  The mounting point on the FZ1 swingarm is too far rearward compared to the FJ. You can make longer dog bones and bolt it all together, but I found that the ride and handling was far less than optimal. I cut off the lug on the bottom of the FZ swingarm, had a block machined to receive the FJ needle bearings and had it welded to the front of the swingarm cross member. It restored the suspension linkage geometry to where I ended up using the original 3XW dogbones and that left me with 5/8" of clearance under the rear tire while on the center stand. I tried the unmodified FZ1 swingarm for a couple of months and never could get it to ride well at all, even with the RPM shock. If you don't like the extra length of the FZ1 swingarm,  you really would be better off to just build a brace for the FJ swingarm and call it a day.

Joe

Yep. Thats one of the reasons I want to move the swingarm pivot back: to keep the linkage geometry correct.

When I measured the two swingarms in the jig, I used the linkage attachment lug as the common point. That's why I'm looking at approx 1.75" off the front and .5" off the rear. Lots of guys often don't understand how much difference even a half inch difference can make in suspension and handling. I've got enough "suspension  time" under my belt to understand what changing the ratios in a progressive linkage does.

Move the linkage mount or move the swingarm pivot, two ways to skin a cat.

My way just does dobke duty by keeping the swingarm length "FJ correct".

And if I end up junking the FZ1 arm, no big deal. I can alawys use more aluminum ingots.

[aviationfred]

Here is a photo of the modified FZ1 swing arm Joe talks about. The dog bone mounting block has been cut off of the cross member and a newly machined block has been welded to the forward side of the cross member.

Fred

[Country Joe]

Well alrighty then, a 114 link chain, that mesh's with GWN's measurements.

Interesting post from Joe on the different locations on the linkage points.
I don't recall anyone in the past noticing that difference, or correcting it like Joe did.

Got any photos Joe?  

Start a new thread so we can return this one back to GWN's mod.

Pat,

Sorry, the photos I took during the mod process were on my previous company telephone. I will see if I can retrieve them from the iCloud.