How do I put a monoshock & ext. swingarm a Mag

No silly beginner questions here, just answers.

This is how:

I said I was going to do this 15 years ago, and using the leftover junk I have in my parts bins once again I was able to whip something up!

This particular installation is a 2003 Yamaha R6 shock and linkage. The Magnum swingarm was cut and lengthened about 6". The top shock mount is cut from a leftover tweaked CR500 frame I had laying around from another project. The lower linkage is welded up to the frame and wrapped around the bottom rear engine bolt (the only SOLID place I could find.)

Anyways, sitting on it and bouncing it feels really good, you can definitely feel the difference of the progressive action over the crappy bouncy factory Magnum shocks.

I am hoping this setup will allow me to get a knee down a whole lot easier in a turn. The rear used to bounce like a basketball and chatter along the pavement when I tried to lean it over and I hit a little bump, VERY SCARY!


1. A little more weight added

2. Longer chains / might need a chain guide or a roller

3. Hard to install/fabricate, not a direct bolt-on and definitely not a beginner's project

4. Not cheap if you have it done professionally or choose to install NEW parts! (The retail cost for the shock alone is about $750, about $1000 total with all the linkage)

5. Won't increase the resale value

5. Longer wheelbase, harder to wheelie (boo-hoo!) Might also make the low speed turn-in action a littler slower.

6. Someone is going to say it sucks or its going to break, blah blah blah

7. Probably won't get me laid (not enough hot moped chicks out there!)


1. No more rubber grommets wearing out (squashing) every 2 months (I hate those damn things)

2. Progressive action

3. Cheap if you have stuff laying around, or if you like to Ebay, or steal one off a parked bike (don't do it, i'll kick your ass if its MY bike!)

4. Longer swing arm travel

5. Longer wheelbase, makes the bike look BIGGER! (I won't look as dorky @ 6'3" and 250lbs riding it) This also should make the bike more stable at higher speeds.

6. Standard aftermarket R6 linkage parts make rear end height easily adjustable

7. The shock stiffness is adjustable

8. Wider tires and even wider wheels can be fitted

9. Proving people wrong when they said it couldn't be done

10. Unique project/one-of-a-kind


Other comments and impressions:

The factory swingarm was cut and smaller diameter THICKER WALL pipe was PRESSED several inches into the cut halves then welded together. This should make the swingarm STRONGER than it ever was before as its double thick, but as a compromise to more added weight. The swingarm does still seem a little long to me, and I worry a little about it flexing or bending. I will watch it and keep measurements and if I see anything changing after everything settles it may be further reinforced.

Right now the rear end ride height is set to keep the front fork rake at 22

Re: How do I put a monoshock & ext. swingarm a


Re: How do I put a monoshock & ext. swingarm a

Nice work! I'm sure that this same idea could be applied to using other, not as insanely expensive, shocks as well. This would also free up some space for mounting disk brakes in the rear as well. Though you'd have to make sure to make the swing arm super duper strong as well.

Re: How do I put a monoshock & ext. swingarm a

Well most sportbike shocks are pricey like that, but you can get used ones for the cost of your lunch money for a few weeks. I just happened to have this one around (along with an R6 swingarm which I will probably never use.)

Check on ebay or in your friends' garages if you're serious about this mod!

Re: How do I put a monoshock & ext. swingarm a

Nice fab work and good job re-using linkage from the bike you took the shock off.

Only huge drawback is now your swingarm is 6 inches longer and so is your wheel base, will make turning a lot more work. Who knows the longer wheel base and the fact it now puts the rider closer to the center of the wheel base will improve handling?

I picked up an cheep sportbike shock awhile ago to do this exact same thing, I plan on mounting the shock on the outside of the swingarm though so you would not need to extend the swingarm.

Let us know how she rides.

Re: How do I put a monoshock & ext. swingarm a

Also what front forks are on the bike?

Re: How do I put a monoshock & ext. swingarm a

For those thinking about giving this a try you could save some time and money by doing it linkless.

Its sick that you used the linkages! Looks good man! that longer wheelbase will sure be stable when the roads get shitty.

Re: How do I put a monoshock & ext. swingarm a

Looks good, but I have a hard time believing that the upper mount will ever hold without crushing the frame, especially with all the leverage now bearing on that shock with the extended swing arm. Glad to see someone do it, though.

Re: How do I put a monoshock & ext. swingarm a

Linkless would cause you to lose the progressive feel of the rear. The linkage amplifies the motion of the swingarm to the shock, I'd have to do the math but I think its like 3:2 ratio.

Also without that motion amplification of the linkage, using that shock just won't feel the same, on a bike this light though, it may not matter.

Re: How do I put a monoshock & ext. swingarm a

Maybe it will! Then it gets more braces!

Re: How do I put a monoshock & ext. swingarm a

I was told the forks are from a CRF50, but to me they just don't seem right for that. They are just too long, actually the same as Magnum length. The steering stem was a little smaller than the Puch stem, but the bearings and races it came with worked well with the Puch bearing cups.

The big problem I had when mounting the triples, was the steering stem was waaaaaaaaaaaaaaaaaay too short for the Magnum frame steering head. Rather than press the short stem out and bore the triples to press fit a Magnum stem, I chose to cut the frame head down about 1" on the bottom and 1/4" on the top. The top and bottom bearing races were also shaved down about another 1/8" on each. I ended up welding my own block onto the Magnum frame for a steering stop.

After tigntening the bearing nut on the stem, the installing the top triple I was able to get about 4 turns on the top nut. I was told once that 2.5 turns is enough for Detroit-manufactured vehicles so I think 4 turns is mighty good for me!

Re: How do I put a monoshock & ext. swingarm a

You can get a rising rate without a linkage. In all honesty who cares if you loose the progressive rate? Its a moped. The biggest benefit is proper damping and aesthetics of course.

Re: How do I put a monoshock & ext. swingarm a

Who cares about progressive rate? That all depends on how and where you want to ride it! Moped or not, haha.

I have some friends that tease me about riding a Ninja 250, too, until we are out in the twisty backroads where anything 600cc ahd up just can't compete! The Hayabusas and ZX-14s are all getting passed by me on the OUTSIDE of a turn. One guy who was actiually making fun of me hardcore earlier that day was whining "its not fair" later that night.

So I highly prefer a smallish bike that handles tight, the progressive rate and damping advantage should stop the wheel from hopping across the pavement in a rear turn and killing myself. It sucks to die on a motorcycle, its lame to die on a moped!

its all about the weeeeeeeee factor! I wanna go weeeeeeeeeeee!

and no I don't expect to race this thing against real sportbikes.

Thats what this is for:

Re: How do I put a monoshock & ext. swingarm a

awesome fab work sir... got to hit the books a bit, and find a friend with a welding kit so i can start doing some real work to my ped.

that sports bike project is lookin freakin sweet too... hope to see some pics once it's up and running too!

Re: How do I put a monoshock & ext. swingarm a

Thanks for the compliments! That sportbike killer weighs about 230lbs or so, lol. Its also a 2-stroke built around a CR500 engine in an all aluminum CR250 frame with lots of other odds and ends bolted on or made to fit. Its going to be a lot of fun!

Re: How do I put a monoshock & ext. swingarm a

Nice work; it's reminiscent of the other mono-magnum project someone (paz?) was building a while back.

Here's mine version, mono-shock and extended magnum swingarm on a pinto. Built about a year ago and is currently awaiting powder, the front fork has also been upgraded to a hydro version. It handles like a dream, the difference is amazing.

Re: How do I put a monoshock & ext. swingarm a

I know exactly what you mean about the small bikes. I ride my RS250 with liter bikes all the time. As soon as it gets twisty, i say bye lol. We had a guy come ride with us on a motarded out crf450. He obliterated the big bikes as soon as it got tight.

Re: How do I put a monoshock & ext. swingarm a

Wanna trade this for your RS250? I've wanted to get one of those and do the paperwork to get it on the street for YEARS! The Ninja 250 is nothing in comparison to that sweet beast. Mmmm yummy. Twice as much power as the Ninja and a lot lighter! Gimme gimme! Pleaaaaaaaaaaaase!

Re: How do I put a monoshock & ext. swingarm a

It took me for awhile to find one. I had to go to texas to get it(Im in oregon). It will take a lot for me to giver her up lol

Re: How do I put a monoshock & ext. swingarm a

Re: How do I put a monoshock & ext. swingarm a

you're going to have to put some biiiiiig tires on that magnum if you want to get a knee down..

Re: How do I put a monoshock & ext. swingarm a

Nah, I used to get a knee down on the thing when it was all factory back in the day. It was DANGEROUS though... but fun! :-D

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