'80 Cm400 Scrambler

Z

Zweihammer

New Member
Here's my current project, one of a pair of sad, neglected 80 Honda 400s I was given a couple years ago. Between the two bikes and a bunch of left over parts from earlier projects, I started screwing around with the idea of a minimalist urban scrambler style. The only "off road" this will probably ever see is the occasional fire road around here.

The problem I am puzzling through now is I am extending and bracing the swingarm while I convert to monoshock. I already have a 2005 GSXR shock to use, but without utilizing the linkage I am finding it very soft, stupid soft. Like an '80s dirt bike soft. I'm a big guy at 230, and prefer my set up on the stiff side. Does anyone have a suggestion for a different, direct acting shock I could look into?

Here's how it sits now, the swingarm will be braced and the lower shock mount was a quick SWAG from a clevis I had just to see if I was in the ballpark.
And, yes, I know the forks are in backwards. Just wanted to throw it together to see how it would look.
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Re: '80 Cm400 Mongrel Scrambler

Looks awesome. It looks like you have a slight extension in your rear arm. If you cut out the stock bracing and replace it with tubular bracing, you could probably fit the linkage in.

I'm on my phone now, or else I'd link to my pix, but check out my cm450 build. You can see how we braced the arm for the monoshock.
 
Re: '80 Cm400 Mongrel Scrambler

Thanks, everyone!
2.3efi, your guys' Cm450 is certainly one of the best, an inspiration. I see you sell extensions for the 360 swingarm, are those swingarms made of two thinwall tubes sleeved within each other like the '80 400s are?
I was more than a bit annoyed to find that was the case when I added the extensions to mine. I realize these were originally designed to a price point, but I can't think what the benefit Honda realized by sleeving two as opposed to a single heavy wall. I will be using .120 wall DOM tube for the additional brace and shock mount.
Cheers
 
Re: '80 Cm400 Mongrel Scrambler

Liking the look of you bike fella, hope your tech mods work out.

Could you change the coil spring rate/poundage and notch up the damping adjuster (if it has one?).

I have a made to measure, direct acting, 13 stage damping adjustable Protech Shock with a 6" 650lb coil-over set up which I can wind the coil up and set damping so plenty of tuning in it. Might suit your requirement?
 
Re: '80 Cm400 Mongrel Scrambler

I did a cx500 with an r1 shock. Changed the spring. Had to jump up to over 1000 lb spring


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Re: '80 Cm400 Mongrel Scrambler

Thanks for the shock options. NoRiders, what did you get your shock made for? Svkustoms, where did you get your updated R1 shock spring?
I just got some '82 Cr480 footpegs to change out the soft rubber stockers. Since I have to add new clevises to the mounts I might move them back a couple inches.
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My next idea to make this more difficult than it has to be is to use another GSXR front rim I have for the rear. I want a 17 (for the wider modern tire selection) with a disc, and the GSXR rear is very wide, both at the rim and the hub. The 3.5 x 17 front matches and fits well proportionally, it just lacks a cush drive. I think I can adapt one from another hub to the unused disc pattern.
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I just can't leave well enough alone. This was supposed to be a quick, cheap build of a free bike.
It's all relative.
 
Re: '80 Cm400 Mongrel Scrambler

After taking a side trip to exercise my ADD,
http://www.dotheton.com/forum/index.php?topic=69776.0
I realized I didn't need another project and applied what I harvested from the XR carcass to my little burro here.

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Right now the seat is just sitting on the frame. I like the seat, possibly not the angle. I want to add a bobbed rear fender.
I am not sure I like the GSXR front fender on this, I may need to make something more old school.
 
Re: '80 Cm400 Mongrel Scrambler

I agree about the angle. With the seat like that you would be sitting on the tank.
Upper frame rails need to be made parallel to the base of the tank.

Just make sure you still have the tyre clearance you need.
 
Well, I remembered, too late, I unintentionally started two build threads that are no longer two builds. If you’re curious what became of this, I am picking the story back up in the other thread-
http://www.dotheton.com/forum/index.php?topic=69776.0
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