1981 Yamaha XS400 Special II Build
A write up on my progress building a custom motorcyclce!
Intro, Inspiration, and Initial Purchase
Over the past few years, I’ve been watching more and more custom motorcycle builds online. Primarily cafe racers, brat style, and scramblers, but also choppers and bobbers.
As I watched these works of art be built, I developed a taste of my own and a vision of my perfect motorcycle. I imagined a bike that was brat style adjacent—subtly different from the original style, retro, yet modern… That’s when I encountered BJ from Brick House Builds’ XS400 (right).
This build checks a lot of boxes for me, and ultimately inspired me to start my own build. In particular, I like the handlebars, seat, front and rear fenders, and the upswept seat hoop. Some things I would change is to keep the original airbox and side covers. Not only does that avoid needing to rejet the carbs, I also prefer the look. Also, I prefer the wheels to be black, and it needs mirrors.
So, I started shopping for bikes. I scrolled Facebook marketplace every day for multiple months, going to see a couple bikes, but never finding the one. I wasn’t specifically shopping for an XS400 either. I was open to any 70s or 80s bike, as long as it had the iconic Japanese Universal Motorcycle (JUM) look. I also specifically wanted it to have a kickstart (I don’t know why but kickstarting a road bike is just so cool to me). I liked the idea of the XS750, or an older Suzuki GS or Honda CB, but none ever popped up in my price range. Eventually, an XS400 Special II came up, asking only $600CAD and only a 3-hour drive away. It didn’t run, and had been sitting for 17 years, but the price was right, it had a clean title and ownership was in the seller’s possession. I went to see it, and met the older couple selling it. It was the bike his wife learned to ride on. I offered $500CAD, and we settled at $550CAD.
Side view of my XS400 when I bought it
The Build Begins!
I got it home with the help of my uncle, who lives only a half-hour from the seller. I took it apart, cleaned the 17-year-old gas out of the tank and carburetors, and it fired right up!
I checked the cylinder walls with a boroscope and they look fantastic, crosshatching and everything! I measured the compression, getting 120psi on the left and 125psi on the right. The engine is healthy and does not require a rebuild! The next step was really stripping it down. Removing all the parts I don’t intend to use in the final build, and cleaning the bike thoroughly (lots of mouse poo, yuck).
After a good clean, I removed the entire wiring harness because I intend to fully rewire the bike to run a modern reg/rec, headlight, and LED brake and turn signals. I also purchased a Motogadget mo.unit blue to really modernize the bike with keyless ignition and the works!
Rewiring the Stator
At this point, I didn’t have a welder or angle grinder yet (for the frame modifications, seat hoop etc.), and still have a lot to do before I’m ready to begin wiring. So, I started some odd jobs. First on the list is fixing the small oil leak coming from the stator wire grommet. This is a common failure point on these bikes and unfortunately, you can’t get a new grommet anywhere. Rewiring, and some silicone gasket maker it is!
Rewired stator grommet.
I used 16AWG wire instead of the original 18AWG to ensure a tighter fit through the grommet, just to be safe. I applied a conservative amount of red RTV, and reinstalled the stator.
Rewired stator installed in the bike
Polishing the Headers
Another little job I did around this time was polishing the headers, as the pitting was really not bad. I used red scotch-brite and metal polishing compound on most of the pipe, but used the heavy-duty green pad for the worst of the pitting. They turned out just perfect!
The polished headers
Upgrading the Headlight
Continuing with the small jobs, I upgraded the original headlight sealed beam unit to a modern H4 replaceable bulb. This was a bit of a funny process, involving the smashing of the original bulb to get it out, and some careful Dremel work to make the modern bulb fit nicely. I bent the tabs on the bulb and used some more red RTV as some glue to make sure it doesn’t vibrate itself loose.
The modified headlight unit
Painting Assorted Parts
Every so often when I got the chance, I scuffed, cleaned, and painted parts I intended on reusing. Such as foot pegs, shifter pedal, rear brake pedal, and the hand levers. I also painted the headlight bucket and battery tray, and rear drum. It’s not included in the image, but I also painted the kickstand and rear drum support.
Assorted parts I painted
Next, I painted the rear wheel. It had some pitting in the chrome, but nothing some scotchbrite and brakleen couldn’t handle. The before and after are amazing! The paint I used is just the cheap gloss black rust paint from Canadian Tire, and some clear coat. I did a couple coats of each.
The rear wheel before prep
The rear wheel after prep
The rear wheel after painting
Finally, before putting the wheel back on, I figured a new sprocket couldn’t hurt. This involved buying a sprocket kit from eBay, as well as some NOS retaining washers to make sure the sprocket nuts don’t come undone. I also had to buy a set of snap ring pliers to get the snap ring back on (getting it off was easy enough with a pair of pliers and a screwdriver, but I couldn’t get it back on the same way).
New sprocket
And here is the wheel, with its new sprocket, installed back on the bike. I had my brother hold up the wheel while I put the axel through all the bits, with a light coat of antiseize brushed on.
The finished rear wheel back on the bike
The next items on the painting hit-list are the front wheel and fork bodies. To remove the front wheel, I started by removing the fender, then disconnected the brake linkage. After that, I undid the two bolts on the left fork holding the axel, and hammered it out. Overall the front wheel was much cleaner than the rear.
The front wheel before disassembly
The front wheel-less forks!
The front wheel all alone :(
The front wheel painting was the same as the rear wheel, though a bit faster as there was less grime (no chain lube gathering road goo). Just a thorough clean with brakleen, then soap and water, scuff with scotchbrite, and a final rinse with water. The temperature outside was getting too cold for paint so there were some issues with getting the paint to stick. I think it still turned out alright.
Front drum brake housing painted
Front wheel painted (1)
Front wheel painted (2)
There was a couple weeks where we got some snow (The gales of November came early), so painting was off the table. I decided to do an initial mockup of the controls, cut the throttle cable to length, etc. I chose some orange grips to match the future color of the bike!
Control mockup left
Control mockup right