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Discussion Starter · #1 ·
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This thread is about my 1980 Honda CM400T project. I acquired this bike on June 26, 2018 with no idea what route I would take with the project. The bike has just over 10,000 original miles on it and has been in storage for 18 years. It was a complete bike, minus a battery, and looked pretty good. I know the previous owner and the bike was well cared for and never ridden hard.
My first thought was to clean it up and get it running, leaving it stock and original. But, that soon lost its appeal and I got to thinking that I was up for a project. After a day of thinking and checking out some pretty cool cafe racer transformations of CMs, I decided to see just how much trouble I could get into with this project.
I set some goals. First, to be able to get some ride time in before the weather turns cold. I'm in Upstate New York and year round driving just isn't for me anymore.
Second, I need to determine just how much riding I can do these days. I have Parkinson's Disease and know my limitations. On good days I'm in good enough shape to ride a bit.
Third goal was to do this project for as little money as possible. I've always enjoyed doing projects with very limited assets. It's a challenge. I mean, let's face it, anybody can spend a pile of money and get someone else to do all the work. That's easy. That's not for me. No 'professional' help at all and keep the expenses to a minimum. I have a great buddy who wants to learn and is willing to put some sweat and laughs into this project, so I do have a healthy helper to do some of the tasks I have trouble with.

With those three goals in mind I set out to define the concept in more tangible terms. I want the bike to be as barebones as possible, with a weight loss program built into the scheme. Simplify is the motif. I want the bike to have a bit of a 'dual sport' persona with a lot of cafe racer look and attitude included.

I figured I should assess the bike a bit more carefully before going any further. Hooked it up to a 12 volt bench supply and almost everything checked out as functional. Something was quirky with the front brake light switch and the clutch switch, but that's trivial. I endoscoped the engine through the spark plugs and all looks well. Carbs are seized. A squirt of oil in the plug holes, turned it over by hand, no problem. Tapped the starter and it cranks. That's good enough for me. It's a viable bike.

So, about thirty six hours after the bike arrived in my garage I took it apart. (Don't worry, I've done this many times before.) Reduced to its simplest components. Parts went into three piles, reuse, sell, and scrap. The seat, lights, side covers, handlebars and controls, airbox, wiring harness, ignition switch, solenoid, tach, indicator lights, mirrors, battery box, windshield, saddlebag hardware, passenger pegs, fork covers, centerstand and assorted brackets, clips and bolts will not be reused, though many of those items will be replaced. I'm still sorting those goodies into the proper piles. (Still pondering the H-box's fate.)

Once the teardown was accomplished a thorough cleaning was done. I pressure washed, sandblasted, soda blasted, wirewheeled, solvent soaked and sanded anything that I planned on reusing. Gas tank was dry and clean inside, but I did a thorough wash just to make sure. All through this process, about two days, I kept a list of what I would need to buy.

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I decided on a color scheme: red and black. Not arbitrarily chosen, this matches my 1980 MGB. Seemed like a good idea to provide a 'sister' for Blythe, my MG. Along with the color decision came the name. Trixie. The CM400 would now known as Trixie, one who brings joy.

Shopping begins. Rattle can paint in Satin Black and Victory Red, and some clearcoat. New battery, seat, bars, perches, mirrors, fork seals, carb rebuilds, ignition coil, lights, choke cable, wiring supplies, switches, front brake cylinder and some hardware seemed like a good start.

The forks. The dust covers were cracked, but there was no evidence of oil leaks. Cleaned them up and disassembled. Drained and measured the oil from each tube. Same and correct amount of oil in both tubes, so no leaks. Checked springs for length, good. Did a near sterile cleanup, new seals, reassembled and put them aside for now. Cleaned the triples, inspected the bearings and races, painted triples and moved on.

When I removed the engine/trans, I discovered that the carbs were not the originals. Someone had installed Mikuni VM32 units with pod filters. Years ago, when I was building lots of toys, Mikuni carbs were preferred over Keihin. A bit of Googling around seems to confirm that is still the truth. So, I'm happy to keep them. Rebuild kits are here, but I haven't touched them yet. I'm still not sure what I'll do about the H-box, and that decision will impact carb jetting. There are numerous posts about the H-box, and it seems to be a topic that creates two camps: The 'Honda designed it so keep it' camp, and the 'get rid of the weight and you'll never notice any difference in performance' camp. I'm inclined to think the truth lies somewhere in between. I always had good luck with crossover pipes on twins, without the complexity, bulk, weight and sheer ugliness of an H-box. I think the sound of the bike would benefit from losing the H-box and going with a simple crossover pipe. Hey, if anyone has some FACTS to contribute to that decision, I'm all ears. So, the carbs will sit for now.

Frame cleaned up well, and looks good with a coat of black paint. As parts arrived, seat, bars, etc., I started dry fitting to see what frame mods would be needed. I cut off the seat mount tabs and the side cover tabs are likely to follow. I'll weld something up for the seat mount. I'll put the engine in place soon so I can determine the size and shape of a box for under the seat to hold electrics and battery.

So, as of today, three weeks after Trixie's arrival, that's where the project stands. I'll try to keep up on posting as I make progress, or encounter setbacks.

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I did check the member map, and it doesn't look like there is anyone in my neck of the woods. However, I know that some folks won't update their location. If anyone is near New Berlin, NY, I'd enjoy hearing from you.
 

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I really like the look you've already achieved, I can't wait to see your personal style of mods for the CM frame.
 

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Discussion Starter · #3 ·
No opportunity to get into the garage today, but I did manage to put together a minimum wiring diagram for ignition/starting. Going with a high capacity pushbutton switch instead of a relay. New-Wiring.jpg
 

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Discussion Starter · #5 ·
I no longer have access to a dyno so I'll go with something either tried and true or something easy to experiment with. Typically, power chambers are useful over a particular RPM range. And, twins benefit from the scavenging of a crossover pipe. The weight of the H-box is down low, so not much of an incentive to ditch it just to save five or six pounds. Only takes a few minutes to weld up a crossover pipe, so that's a decent option to experiment with. I should start with the H-box installed as a baseline. Thanks for the info!
 

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My understanding is that it was designed to enhance low to mid range performance. The 450 versions have holes drilled in the bend inside that would allow a free flow effect under high exhaust pressures/high rpm.
With the weight below the center of gravity it actually helps balance the bike to a degree.
 

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Discussion Starter · #7 ·
Mikuni VM32 rebuild

Carb rebuild kits arrived! I got an early start and took one of the VM32 carbs apart. Inside was very clean, no sediment in the bowl, jets in good shape. I cleaned and soda blasted one of them. I'll leave the jet sizes the way they are for now since I know the bike ran very well 18 years ago. I've decided the H-box will be included in the exhaust system, though a mod or two may be down the road.

Estimated days until first ride: 16.

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