17" wheels, aluminum swingarm with monoshock upgrade

If your a devout Yamaha purist don't read any further. You may find the following sacrilegious or offensive.
I've slowly been gathering parts to complete the modifications of my XJ550 Seca. Other than a couple frame modifications, to accept the monoshock set up, it's a fairly straightforward forward operation with basic fabrication skills.
I'll be installing the previous items over the next month or so and I'll document accordingly as things happen.
In case you were wondering this is all Suzuki stuff, GSXR and SV model specifically. They sell alot of them, therefore alot of them get wrecked and parts are plentiful.

 

Straightforward... basic fabricationing... riiiight! Can't wait to see how it goes!

 

Well, if one is used to building stuff out of steel, a swingarm swap is basic fabrication (I'd say it's far easer than building a single-wheel trailer from scratch). The only tricky bit is making sure all the math was done right so the suspension works as intended (or better).

 

Would like to see this when done. Might all work for the 550 as it is chain drive , not so much on 650/750/1100 being shaft drive .

 

I think there is an old thread with this same swingarm swap. I do know that there have been several monoshock builds posted here. Some with swingarm swaps, others without.

 

Sort of like this.....
https://xjbikes.com/forums/threads/my-seca-ii-scrambler-project.65159/

 

Sigh. I guess Matti is the basic one here...

 

There is nothing wrong with basic. Without it there could be no path to becoming advanced.

 

I might be able to fab a bracket, if I had to, but it'd be fugly. I guess I'm more of a bolt-on guy.

 

is that like a wheelbarrow ?

 

Somewhat, but better (unless you're gardening).
There's pics of it in my gallery showcase.

 

The first of many straightforward and basic "alterations" to make stuff fit. The mount for the swingarm linkage favors one side, nearest the chain. I want this centered for my application, so I cut the mount off and made up an aluminum filler plate out of 5/16" 6061 for strength. Then I'll either reuse the old linkage mount or make up a new one and weld it on. The last image shows the red marks where I have to narrow the swingarm to fit the frame of the 550. I'll also attach a bracket for the brake stay rod.


To finish up the swingarm I'll glass bead the entire thing, wire wheel and polish it before clear coating. I'll post pictures of the finished product.
I also put together the underside mount for the linkage pivot that will go where the center stand used to be. I'll include that at the time of install when I begin frame modifications. I'll yank the motor, airbox and whatever so nothing gets barbequed when the time comes.
Yes, I'm keeping the airbox....
Like I said, straightforward and basic stuff here.

 

Yup. Step 1 is already beyond "basic and straightforward" for me!

 

That's easily solved. Get you some tools and some scrap and start making mistakes

 

you have the swingarm bearings figured out yet?

 

Yes, I have to shave 3mm off each side so I ordered bearings to fit appropriately. Since the original swingarm pivot bolt will be used, the ID of the new bearings will match the OD of the stock pivot bolt. I have a sleeve to make up the difference on the spacer that fits between the two bearings in the middle of the swingarm bearings. The end caps off the old set up will be used to keep all the crap out.

 

*DISCLAIMER*
Any modifications done are subject to being under the heading: IN THEORY. I've thought everything out, I think. But something will go sideways, guaranteed. I'll be glad to share any of these challenges as they arise and they will.

 

Carrying on with the swingarm install, I cobbled together the underside pivot mount for the shock linkage. It will only be half as long as it is pictured to provide the correct geometry for the shock absorber. I'll notch it with a hole saw and it will side completely over the bar that used the be the mount for the center stand. Gussets will be added so it's not cantilevering all by it self. It needs to be beefy and slightly over built being the frame is not a monoshock specific frame.
I made a new pivot point for the swingarm linkage out of chunk of 6061 alcad aluminum that my buddy who works for Boeing brought home in his lunch box. The brake stay arm bracket was also made up but the material was purchased legitimately.
To get the swingarm aluminum parts welded up I decided to send it to my local fab shop. I was going to use a spool gun and MIG weld everything up and call it good then I saw some work the local guy did with his TIG set up. Effin' thing of beauty and much stronger better penetrating weld quality. Two weeks or less turn around time for $150.00 and a piece of mind that it will be stout and better than new.
Count me in.

 

That's actually a likely next project for me. I figure the old upper shock mounts make a nice attachment point (allowing vertical pivoting) and the BMX bike I stole my bars off can provide the head tube etc for horizontal pivoting. Am gonna use a 55 gallon metal drum for the main structure / cargo area, unless I can get my hands on something more aero like an aircraft drop tank.

Yer not kidding. When I started my bike, I got a setup like yours plus another shock that was a bit stouter ... all for $20 on Craigslist. However, all the shocks worked out as too softly sprung by my math (for an XJ750 Seca). I still found a use for the pivot though. You might be interested in some of the pics of my shock mount, will see if I can dig them up. IMO the mount itself doesn't need to be beefy, it just needs to distribute stress into the frame well. Its bolted to (bung welded into) a rectangular tube that beefs up the cross tube, and an aluminum block that new (longer) engine mount bolts thread into. (And yes, I did most of the work on a mill.) Part of the reason for the bolted assembly was that, if I ended up with the bottom end of the shock in the wrong spot, it would be fairly easy to make a new mount, replacing just that one part.

Mine stood up to a test load of 2,000 lbs (pulling up on axle with frame secure by engine mounts and shock replaced with rigid strut), and has about 3000 miles on it at this point.

 

Yup. More "basic and straightforward"! Lol
I love that you guys are doing this stuff.

 

Your set up looks sweet and bolt on is cool also! Nice work. It's reassuring to know that this modification has been successful for others. Thanks for the pictures...
I agree with you about the lower mount needing to distribute the force of the suspension movement evenly. The 550 frame is a waif of a frame so I'm going to give it all the help I can with some beef.
My lower mount will use triangulated 3/16th gussets to distribute the force equally.
The top mount is going to be an X DOM tubing configuration that will be slightly angled towards the rear of the bike. I'll come off vertical part of the frame that runs in the middle of the air box and back to the angle frame member that runs up to the existing shock mount. The top of the shock will mount slightly behind the center of the X. All that beef will be stuffed under the air box and battery so a 11" shock is the maximum length to make it all jive. Ducati fortunately runs shorter adjustable rear shocks than most others on their bikes. That's what I'm leaning towards at this point.The one I got in my CL package deal,off a GSXR, is 14.5" long. No bueno.

 

⬆️ "in theory"
(subject to change and probably will)

 

On no sir. In hypothesis.

 

True that.
Its slightly more than a wild guess shot from the hip with smoke in my eyes.

 

So this guy from England, his name is Chilly Hill (honestly I can't dream this shit up if I tried), sent me a email with pictures of a bike he built several years ago. The 15 pictures detail the monoshock conversion he did on his XJ550. He used a a mid 90s YZF600 or R6 to do his swap. Evidently he checks out the forum out sometimes as a guest, saw this thread, was able to track me down and wondered if some pictures would help. This is very similar to what I'm going for as my end result. Thanks Chilly!

 

Today was a week since dropping off my swingarm to have it TIG welded. I thought I would give a call to see if any action happened with it. The guy at the welding/fab shop said he would have to call me back with the status of it. Three hours later he got back to me and he tells me that they are unable to locate my swingarm. WTF was my reply then I asked how things like this are handled. He was unsure. The owner of the shop then called me and told me that he had a similar issue about a month ago with a chunk of aluminum going missing. I told him "one of your guys is possibly ripping you off and recycling the stuff for cash." He relucantly agreed that something was fishy.
Luckily I dropped my stuff off with the owner and received paperwork to claim the part. He reminded me that the small print on the receipt states that they are "not responsible for damaged or misplaced items". I called BS on that and told him to fix things however possible. He promised me I will have a swingarm even if he has to build one himself. This could be cool, I thought.
Tomorrow he is having the entire crew, 7 guys plus him, in for half a day to do a comprehensive shop cleaning.(the place is a train wreck) He will get back to me tomorrow afternoon with an outcome if anything shows up.
Hopefully my parts will turn up or someone's head will probably roll.

 

This really slows things down...

 

Im not saying it won't work... But I allways roughed in and tested first.... You got some real nice fancy looking brackets and stuff, but if you suspension geometry is off even 1/4 inch somewhere with that Pro-link style set up...
Dude, regardless, I'm right interested to see it on the road! keep us posted!

 

This bike is my all time favourite 550.. It was featured in 'Practical Sportsbike' a few years ago.. I also saw it on ebay a while back as Chris 'Chilly' Hill (get it) was trying to sell, not sure if he ever did. I couldn't that's for sure. If I get the time I'll a) locate b)scan - the article.

 

Fingers crossed that I figured my angles correctly. I'll bite the bullet and make a decision on which shock will be used shortly. Having the angles correct IS a big deal and concern. Will keep you posted.

Very cool straight up dude! One hell of an tatoo artist as well.
I'd love to see the article associated with his bike. He has an eye and knack with older bikes based on other builds I've seen of his.

 

I had a suprized visitor about an hour ago, the fab shop owner, my swingarm didn't materialize or anything. He was kind enough to drop by with an envelope containing $200 cash to cover my time making parts plus a new swingarm. Very fare but frustrated dude because one of his guys is pilfering not just parts but also materials. Who knows what else too.
I offered him a beer and told him we were more than fair....

Back to CL or eBay to get the ball up and rolling again.

 

Good guy, understands the value of his reputation...

 

Found and ordered another swingarm. A little change of plan; still using a Suzuki swingarm, same dimensions but this is an all steel version off a 2009 SFV650. The SFV650 was a beefier version of the uber popular SV650 that had a short production run of about 6 years.
It comes with all the stuff to make it a complete assembly. I'll be able to center and weld up the linkage mount and brake stay arm bracket myself being its steel.
I'm trying to avoid anymore delays going this route.
You can't blame me.....

 

.

 

Got the new swinger this morning
Centered up the shock linkage mount
I plan on running a 160/60 R17 tire in the rear and a 120/70 R17 in the front.
The rear wheel will be moved back just about 1 1/2" from it's normal location. The swingarm is 2 3/4" longer than the current arm. This will definitely change the way the bike handles. The added length along with the wider 17" tires will be a welcome improvement.

 

This is the rear shock I will be using. Its off a 2007 R6 and its fully adjustable. It's one of the shorter shocks available at 11.3" in length eye to eye. Everything has to mount up under the airbox and battery so it's tight but doable. To do this right everything has to be removed. Before I get in deep with the rear end stuff I want to dial in the the front wheel fitment 100%. There's plenty of nice weather coming up. I'm going to take advantage of it and ride before breaking the bike down to work on the frame modifications. There's plenty of stuff to get ready prior to that.

 

To make the front rotors line up 5mm must be milled off of each side of the wheel hub. There is an abundance of material on the hub of the TL1000 front wheel that will be used. The integrity of the wheel won't suffer from being shaved down as it's over built to handle the heavy bike it's from. The lip that serves as the stop for the bearing race will also have to be bored out or actually in, as well to recess the bearings inward as well.
This isn't CNC millwork it's all time consuming hand milling done on a dinosaur Bridgeport machine. At least a day's worth of messing around at my buddies uninsulated metal clad shop building a.k.a. "The Oven".
Yes, I admit, we're kind of crossing over the line of "straight forward and basic" at this point. This is one of those challenges I mentioned earlier. I welcome them....

 

Today was 15 degrees cooler than usual so I spent the afternoon milling the front wheel down. It went really well for the most part, it's just a slow process. The final piece of the puzzle will be making up a notched plate to run the speedo drive. I'll sleep on that one or it'll come to me while I'm taking my morning dump. I do some heavy thinking and problem solving on that porcelain seat. TMI....
The new bearings will be in on Tuesday so I plan to have the front dialed in by next weekend.
I am kind of concerned about my chain alignment being a potential issue. From my measurement benchmark it seems as if there may be 5-6mm difference. That is the limit of offset under the front sprocket cover. I'll be running a 525 chain so that will gain about a CH of clearance. A offset front sprocket may be part of the revised upcoming plan.
I'll also start to pull the motor, exhaust,air box and stuff this coming week. I have three days of PTO to use up the following week. We'll see what I can get accomplished with the frame changes at that point.
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I won't be posting anything more from this point on unless I have pictures to accompany the subject matter.
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Progress as of today, upside down or sideways , for some reason.
Still waiting on a few parts.
Tires will be in next week.

 

Progress has slowed due to adverse reaction from all the smoke in the air from wildfires. All neighboring states and Canada are burning up, bigtime. I'm a smoker too!
Received new tires and a couple of odds and ends. I ended up ordering an 10mm offset sprocket to line everything up correctly.
It's getting there....
From this angle the rear sprocket is not visible. There is just over a 1/4" clearance between the 520 chain and the tire sidewall edge. Works for me... When the shock shows up next week I can button this up. This is close to the ride height. A black tire hugger goes on the cross for the swingarm
Alot of work on the rear shock mounts and frame has transpired that no one will probably even notice. That's fine. It's all tucked under the airbox and where the center stand was.

I happy with the bad attitude the bike seems to have now.

 

I'm very impressed with what you've done, but given all the extra grip you now have, does the original frame have enough stiffnes to cope with it? Appreciate you haven't finished the back end yet.

 

Before undertaking this project, the frame strength and ability to be modified, was researched as much as possible. The XJ550 frame is very similar in design to the FJ600/XJ600 frame. Based on those models differences, in respect to how the rear suspension is set up, I mimicked a similar design to my frame to make it a monoshock.
I'm not an engineer or chassis specialist so there is always an amount of risk in doing this type of modification. The percentage of risk varies based on: common sense
experience
build quality
material quality
in depth research
design adaptability
safety and ridability of finished product
I believe in overbuilding things when possible and practical. So I've incorporated that into the project. I've added gussets and braces where applicable.
Over everything else, safety has been my biggest concern and main focus. Putting something dangerous and sketchy between my legs isn't how I roll.
Here is one of the few frame modifications you can see. There's plenty more that are hidden.

 

It's good you've considered it - I wasn't thinking in terms of it failing, more like flexing and undoing all your hard work.
The modern honda cbr? Is like a modern version of these old bikes, with substantially bigger (therefore stiffer) tube diameters - they must have had a reason?
When I sketched the replacement back end for my hard tail trike I didn't think it would need any more than a triangulated addition. When I was putting all the bits back on I became aware the whole thing was flexing torsionally. It turned out the bike frame it was built on was the culprit. So I added diagonals - behind the headers, under the seat, under the seat rearwards, and at the bottom of the new back end. Using a straight tube held against the frame to detect movement gave me a measure of how effecive each mod was. Anyway, I digress, bikes aren't subject to the twisting forces of a 3 wheeler, unless of course things get really hairy and it turns into a tank slapper.
It will be good to get a report on how this handles when finished, good luck with it.

 

Thank you.
I've accomplished plenty on the project this past week. Gonna put it on the back burner for a week or so. You know it's time for a break when dream about "triangulation" and "torsional flex".
On a side note: my new shock was delivered today. I ended up going with the rear shock off a 2009 R6. I chose it because it has less bulk on the top mounting area than other shocks in regard to the resivoir location. I'll be using the triangular linkage coupling joint it comes with and making "dog bones" to fit.
My offset front sprocket is two weeks out being it's not an off the shelf part. When I get it I will have to drill and tap holes for the retaining clip M6 bolts using a cobalt bit and tap. It's original application is intended for a RZ350 or a Kawasaki H2 which use a castle nut on the threaded spline and a tabbed locking washer to hold it. Being it's hardened steel, it's going to be a small challenge to thread. It's doable. I'm open to alternative securing options....

 

Just don't do this.

 

OMG!
Thats not a bad welding job, if it's any consolation. The thought never crossed my concious mind....
Asleep? Maybe.....

 

When I woke up this morning I had a serious eye problem. I bothered me so much I couldn't see going into work, so after a couple of extra hours of sleep I woke up and was fine. Go figure. So I went out to the shop and had a productive day...
I got the shock mounted up after a small tweak to my mounting bracket

and I was able to sort out the rear brake caliper mount and stay arm.
Now I'm going to give it a break until the final shipment of parts arrives.
Honestly.

 

Everything I had been waiting on showed up this morning.
So.......

I was able to drill and tap the offset sprocket

Finished up the rear suspension


The static height of the rear is about one and a half inches too much so I have another set of links I'll install to adjust it. Everything in the rear suspension cycles nice and smooth. With two on the bike it squats down but not like it will bottom on the fender. A road test is the only way to figure out what's what.
Another couple of weeks should do it.

 

Dang..

 

+1

If the frame tubes were a tad thicker you wouldn't know that it wasn't built that way to begin with.