250R Swing Arm Extension Project

[Mr. Sandman]

After way too many years of riding my 250R with nothing but brute strength to keep the front end down on launches while hill shooting the dunes, I finally decided to extend my swing arm. Now, I like to wheelie as much as the next guy, but ever since I bolted my 310 kit on a few years ago, the unwanted wheelies had gotten ridiculous. So….after reading up on extended swingers both brand new and stretched stockers, I decided to undertake the project myself. After all, how hard can it really be? I only wanted 4 more inches but didn't want to spend a fortune to get it.

I decided not to cut up my original but shinier than stock swing arm so I bought a thrashed one on ebay. A little measuring here and little measuring there and I broke out the hacksaw. Fifteen minutes later, the swing arm was in two pieces. A little more measuring to see what size steel I needed and I found out that the Japanese in their infinite wisdom used a size of rectangular tubing that cannot be found at my local steel supplier. With an O.D. of 1 3/16” x 2 3/8” there was only one thing I could do to make it work, look clean when finished, and still be plenty strong. So, I bought another swing arm on ebay to use a sacrificial steel supply.

One thing I noticed about most stretched stockers is that they didn't have clean lines due to the weird angles that were left after they were welded up. Because the swing arm gets narrower as it gets longer, the extensions have to be angled out to meet up with the pieces of tube left on the carrier. Now I’m sure there are other ways to go about it, but I decided the easiest way would be to cut the dog bone mount yoke right down the middle. By doing it this way, I was able to spread the tubes apart, insert a 5/16” spacer to make the narrowed end wider, keeping everything straight without any weird angles and not affect the pivot point where it bolts up to the frame. Going this route on anything longer than a 4" extension would probably not work as the pivot wants to bind on the swing arm bolt. But, a problem with doing it this way is that the dog bone mount tabs are also 5/16” further apart as well, so some new filler tabs were made up to weld into place to get the correct dimensions back. The semi-trick particle board extensions were made up first to make sure everything lines up as planned. Now it's time to start cutting up the sacrificial swinger. More to follow as things progress.

[BigGreenMachine]

Very nice, clean cuts and great planning. Nice work man!

[MyMistress86R]

How's this project coming along? Did you ever complete it and how did it work out?

I have one small concern about your methodology in spreading the swinger in the shock linkage area, but I wig out about small inconsequential details, so it likely isn't an issue. Anyhoo, granted that 5/16" isn't all that much, but did it do anything to the alignment of the tubes for the swingarm bolt? I can visualize the forward crossmember acting as a pivot point when you spread the rear crossmember and bringing the forward pivot tubes slightly closer together and changing their alignment as well.

It's likely that the forward crossmember is rigid enough that nothing moved at all, but it never hurts to wonder.

Thanx,
Todd

[Mr. Clean]

How's this project coming along? Did you ever complete it and how did it work out?

http://www.3wheeler.org/vb/showthread.php?t=27865

[Mr. Sandman]

How's this project coming along? Did you ever complete it and how did it work out?

I have one small concern about your methodology in spreading the swinger in the shock linkage area, but I wig out about small inconsequential details, so it likely isn't an issue. Anyhoo, granted that 5/16" isn't all that much, but did it do anything to the alignment of the tubes for the swingarm bolt? I can visualize the forward crossmember acting as a pivot point when you spread the rear crossmember and bringing the forward pivot tubes slightly closer together and changing their alignment as well.

It's likely that the forward crossmember is rigid enough that nothing moved at all, but it never hurts to wonder.

Thanx,
Todd

It's getting there. It's just been sitting more than I've been working on it. I was concerned about the same thing as you but the pivot point dimension only changed by about 1/32". Still though, once I had it mocked up I remounted it to make sure it swung freely through the motions and didn't bind. Next stop, the chrome shop!

[oldsking86]

Very nice job! Im actually in the same boat is you for doing a +4 or +5, still debating.. Great technique though, helps me out a lot for my new swinger in the works

[Mr. Sandman]

Another two months later and it's finally done. I just need to put it back on and take it for a spin. Hopefully that spin will be out at Dumont next week with everyone else from .org

While I was in the fabricating mode I retrofitted some Raptor footpegs to my peg mounts. I would've stuck with genuine Honda parts but I liked the look, size and feel of the Raptor pegs better than the Honda 450R pegs. No biggie though as I still bleed Honda red.

[3WW Star-Yamahondaman]

WOW .... LOTS OF CHROME !!! send me some of that CASH !!!
looks NICE !!!

[Mr. Sandman]

Here's the final product in all it's glory. I'm very pleased with my additional length, girth and overall size...wait a minute. I meant to say the additional length is very helpful to keep the front end down when hill shooting but it still wheelies with ease and a blip of the throttle. The rear shock is definitely softer but not so much that it bottoms easily. I just wish I had done this years ago.

[steven 250sx]

looks good job weell done

[Red Rider]

The swingarm looks good big bro. So do them phat boots!