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Author Topic: Honda RS1000 - CB400F Mini Replica  (Read 4081 times)

Offline Rick4004

  • Posts: 73
Honda RS1000 - CB400F Mini Replica
« on: Feb 09, 2019, 17:42:23 »
I've just started a new project that I hope doesn't drag out too long, and doesn't take up too much time. Most of the parts used will be just stuff that I already have sitting around from past projects.
My inspiration - Honda RS1000 Racer Circa 1979.
These go by various names, RCB900, RCB1000, RS1000. These bikes were built from 1976-81 in various configurations, in fact, being hand built, it's doubt-full that any two were exactly the same. If you do a google search you will find lots of different seats/fairings/tanks used over the years. The last ones built in 80-81 even had mono-shock rear ends.
To me, the iconic signature features of these bikes is the solo seat, long tank, half fairing, and the curved muffler.
Anyway, as a teenager, these were my favorite racebikes, and when I was 17 I bought a 1980 DOHC CB750F that was the child of these racebikes.
I've got enough CB400F rolling chassis sitting around that I decided my next 400F should be an mini endurance racer.
Attached is a photo of the inspiration, and a quick CAD model of my 400F mini replica.
« Last Edit: Feb 20, 2019, 19:55:11 by Rick4004 »

Offline Rick4004

  • Posts: 73
Re: Honda RS1000 Mini Replica
« Reply #1 on: Feb 09, 2019, 18:26:07 »
I wanted to laydown the shocks to get that period twin shock race look. Step one was to measure the physical dimensions of the RS1000 and input those parameters into Tony Foale's suspension software. I have a 1/12 Tamiya scale model of the RS1000 and used that in conjunction with photos I was able to gather the dimensions, and estimate a spring rate. This gave me the spring force at the rear wheel and the rising rate curve.
I was then able to transfer that data to locate the shock mountings on the 400F. The spring force on the 400 is a little less than the 1000, but the 400 should be lighter, so I think it's a good starting point.

Offline Rick4004

  • Posts: 73
Re: Honda RS1000 Mini Replica
« Reply #2 on: Feb 09, 2019, 18:36:14 »
I bought these generic chinese shocks off of ebay. 340mm long. My research indicated that these come with either 7mm or 8mm diameter springs on them, depending who the seller is. I chose the seller based on the fact that it was specifically stated in the description that the springs were 8mm. Of course, when they arrived, they were 7mm. I think the spring will be too light and I'll be searching for heavier springs.
I cut off the old shock mounts from the frame, cleaned up the tubes, and used some 3d printed marking guides that I built off the CAD data to position the holes for the new shock mounts.

Offline hooligan998

  • Posts: 274
Re: Honda RS1000 Mini Replica
« Reply #3 on: Feb 10, 2019, 02:07:33 »
Very cool.  In.

Offline julian.allard66

  • Posts: 286
Re: Honda RS1000 Mini Replica
« Reply #4 on: Feb 10, 2019, 05:41:44 »
Tamiya make a model of the RS1000, you might find it helpful for measurements etc.

CBX550 engine would give you a twin cam engine cheaply

Sent from my SM-T560 using Tapatalk


Offline Rick4004

  • Posts: 73
Re: Honda RS1000 Mini Replica
« Reply #5 on: Feb 10, 2019, 10:22:12 »
julain.allard66 - Yes, I have the Tamiya model, I took some measurements off of it when inputting the suspension parameters. The CBX550 would make for a cool project, they were fast for their day. But, they are also pretty rare, and parts aren't easy to find. As I stated, this is a cheap build using existing parts, and I have lots of 400-4 stuff sitting around.

Offline Ichiban Moto

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Re: Honda RS1000 Mini Replica
« Reply #6 on: Feb 11, 2019, 13:44:31 »
Chris has things for those shocks and this tool:

http://chrislivengood.net/wp/advanced-spring-rate-estimator-new/

ps. anyone know Chris' username here?

Offline Rick4004

  • Posts: 73
Re: Honda RS1000 Mini Replica
« Reply #7 on: Feb 12, 2019, 18:58:31 »
I wanted to disassemble the shocks, check them for assembly issues, and rebuild them with fresh oil. But first, I needed a spring compressor that fit. I have an S&W compressor, but it wouldn't work on these shocks. So, out came some flatbar, nuts,bolts, and threaded rod. Worked like a charm.

Offline Rick4004

  • Posts: 73
Re: Honda RS1000 Mini Replica
« Reply #8 on: Feb 12, 2019, 19:10:48 »
ICHIBAN - I emailed Chris and he was very helpful. I was going to just purchase the shocks from him already rebuilt, but the shipping from the USA to Canada was $65USD. I ended up buying them direct from China for $85 US shipped to Canada, so I figured I'd might as well just rebuild them myself.

Offline Rick4004

  • Posts: 73
Re: Honda RS1000 Mini Replica
« Reply #9 on: Feb 12, 2019, 19:16:06 »
I wanted a better swingarm for this project, something longer, wider, and stronger. I had a CBR600F1 sitting here with all the parts that I need to make it work. Only problem is that it is 20mm too wide to fit in the frame.
Cutting out the 20mm is the easy part. Getting everything lined back up and keeping it straight during welding will be the harder part.