Swingarm question anyone know?

[barelycompetent]

Hey all, been away for a bit, and sold my 750 a few months ago, but still wrenching and riding, just on a new ride lol!  I still have my 1981 Honda CM400C, and Im currently giving her a winter makeover.  I want to change the stance on her a bit, drop the back end down some.  I saw a cm400 where the guy had either stretched the swingarm a few inches or used a different swingarm, but it lowered the back end down and really gave it a cool looking stance, kind of low and mean, at least I liked it lol.  So my question is this, does anyone know if I can use a swingarm from a bigger bike?  Im just wondering if a 550, 650, 750 swingarm woud fit on my 400 and if it would be longer?  Thats just one option Im looking at before I take my swingarm off and have it cut and welded.  I figure you guys could answer that one for me lol.  Thanks in advance.

[TOOLS1]

Just move the swingarm mounts further back on the frame. It's a lot easier to do.
TOOLS

[shinyribs]

Hmm...tough call between stretching the arm vs. moving it's mounting position.

I agree with Tools that new pivot mounts would be easier than stretching the arm, unless the arm is tubular and has parallel legs, which I'm not sure if yours does. But chain geometry would be my concern. When I first started on hackjob (remember that forgotten build....?) I was wanting to move the pivot location. As it turned out, that was gonna create a lot of issues. The placement of the swing arm pivot in relationship to the front sprocket is critical in order to keep chain tension somewhat consistent throughout its arc. When you alter that position stuff gets crazy fast. When I looked into stretching my.wheelbase 2" I mocked it up and checked for chain clearance. My concern at the time was the chain dragging frame tubes or the swinger itself. What I discovered was that my chain (while travelling thru the arc) would go from super tight to about to flop off. So I scrapped the idea and just went with the extra 2" the new arm was already giving me. A 2" longer (or any amount, actually) swing arm will disturb chain arc tension also, but the effects are extremely minimal compared to moving the pivot away from the front sprocket.

My $0.02, mock it up and see what's up. In the end physics may make the decision for you.

[Lucky 1]

I would not cut and weld the swing arm.
You can buy shorter shocks  and get the same low mean look.

[barelycompetent]

Thanks for the replies, all things to think about.  I really dont want to put anymore money into this bike, its only a 400.  I may end up just leaving it as is.  Im not really decided yet.

[shinyribs]

Hey Barely, do you have a pic of the bike you saw that looked lowered? It might not have been a stretched arm, but only relocated shock mounts. Maybe they slid them back to lower the bike. Check Tools' cafe build (I love saying that :))  and you'll see where he did just that. Works good, looks good, easy to pull off.

[barelycompetent]

Unfortunately I cant find the pic again.  I looked at my bike, and there is no way to move the shock mounts back any further, they would get in the way of the chain adjusters.  It was definitely stretched, but I think luckys idea of just buying shorter shocks might work just as well.  I was thinking 10.5, anyone know a good source to find a set of shocks?  Preferably not too expensive lol.  Thanks.

[TOOLS1]

Cycle-X
TOOLS