1978 HONDA HOBBIT x 1980 MOTOBECANE SEBRING

This is a mash-up of a 1980 Motomarina Sebring and a 1978 Honda Hobbit. The Hobbit PA50II is the perfect moped engine platform and the Sebring has a nice large frame.

This is my current moped project still in process as of 12/06/2024.

I bought the yellow PA50II Honda Hobbit first in 2021 for $300. It needed a few things to get back on the road. I got a SHA15 Carb and intake. The intake moved the carb outside of the subframe so it would be easier to tune. I also installed a Proma Circuit exhaust, new piston and rings. There was 30 year old gelatinized gas in the tank that I cleaned out.

All of the Philips head screws holding the intake on were striped so I had to drill them out. I replaced them with allen bolts. The headlight bucket was smashed so I put the old, plastic Concord headlight on. Then I made a little bracket for the speedo with some scrap steel and a hose clamp. I got the stockish Hobbit running and one of my friends used it in the first Black Pipes rally in 2022.

I was using the Hobbit as a loaner for awhile and then the Sebring came up on FB Marketplace. It was the geographically closest moped I’ve ever purchased. It was literally at the end of my street and it was only $200! It was only listed for a few minutes when I saw it, I messaged the guy and ran and got it right away. I think I have a photo of every moped from the moment I bought it, LOL.

The Sebring had the Morini MO2 automatic 2-speed transmission. At the time there was only one 60cc kit available and it was impossible to find. That is why I decided to swap engines with the Hobbit. My Concord frame is sooo small so I finally wanted something fast with a big comfortable frame. The gas tank also holds over 2.5 gallons which is huge for a moped.

I took the engine off and sold it on Ebay for $250. So after shipping and fees it was basically a free moped roller.

As soon as the engine sold I was ready to start hacking up the frame. I acquired a sacrificial Hobbit frame to cut the motor mount off of. I used the red donor frame in case I messed up. I also cut the old motor mount steel off the Sebring frame. That was a huge chunk of metal. It held the engine, side covers, center stand and swing arm. I didn’t need any of that any more because it’s all included in the subframe of the Hobbit. My dog is snoring on the floor in front of me as I type this, Lol.

I don’t know exactly what my thought process was but I decided to weld the red motor mount to a piece of angle iron. I thought that might strengthen it? Then I welded it to the Sebring frame. Even though I was free-handing it, it came out perfectly straight. Unbelievably, perfectly straight. I’d never be able to line something like that up that perfectly again.

I moved the motor mount back a bit compared to the original Sebring wheel base. That put it about 3” longer than the original Hobbit wheel base. That means I would have to extend the rear fender out but I’ll get to that later.

I’ve been a hobbyist MIG welder for most of my life but I never really clean up the welds. I know a lot of people will be looking closely at this in person so I decided to try this time. After grinding them down there were a lot of pin holes. I re-welded some to fill them in but it was a pain.

I had heard silicon bronze was an easier way to clean up welds. This was my first attempt at using it. I found a spool in my welding cart and I have no idea how it got there. It worked pretty good. It sticks to the steel and is softer so it is easier to sculpt.

The shock mounts on the Sebring frame were much wider than the Hobbit swing arm. You can see in this photo how bad the camber(?) is on them. You can also see they mount on the outside of the Sebring frame. I made a bracket that moves them to the inside of the frame so they mount vertically.

I had a friend bend a piece of 3/16” steel plate into a “U” shape. Then I drilled the holes for the shock bolts and welded it to the frame under the seat. The shocks aren’t perfect but they are much closer to square.

The bottom of the shock mounts to a very thin, sheet metal tab on the subframe. I decided to practice my pipe bending skills and made a stabilizer for the bottom of the shocks. I drilled a hole in the old air box section of the subframe and it bolts right on. There’s a video of the build process on the @theroadhaus Instagram, the next photo set is all screen shots from the video.

The Sebring came with a mix of wheels. It had a spoked, 16 inch, Italian front wheel which definitely did not come stock. It had the rear 5-star that was original though. Before I decided to do the engine swap I found a front, Italian, 5-Star from a Motron (so it is bronze in color).

The Hobbit had spoke wheels that were in great shape. When I did the engine swap Treatland had just released reproduction Hobbit 5-stars so now I could use the bronze front wheel and I got a gold Hobbit rear wheel. The Hobbit rear wheels are proprietary to the Hobbit because of the transmission. Eventually when everything is done I will get them powder-coated to match.

I ended up selling the stock, spoked Hobbit wheels for $160. I stripped the frame and sold everything to recoup some build expenses. I sold the Hobbit handlebars, fenders, forks, seats, rack, frame, shocks, fuel tank and every little piece I could.

The key to disassembling the Hobbit transmission is putting the big, weird nut directly into a vice. Then you just grab the tire and unscrew it. It’s amazing how easy it makes things. Video on Instagram. Here are some photos of the wheel swap:

The CNC’d brake plate is really nice but it has a flaw. The actuator arm is too small for the brake cable. The Hobbit rear brake cable is unique so I like to use it rather than making one with knarps. The bolt at the end of the cable doesn’t fit inside the arm.

I disassembled mine and milled out the center of the of the arm so the cable fits. The knarp at the end also didn’t fit in the arm so I milled that part out too. Video on Instagram.

The forks might have been the biggest single project on this build. The stock forks are tall and robust(ish) so I wanted to keep them. The problem was the threads on the post/tube in the triple tree were destroyed. I couldn’t find any replacement for just that piece so I decided to make one from a solid piece of round stock.

I drilled out the center on the lathe and cut each of the steps into the tube. There was a step at the bottom so it won’t slide out of the yoke and then a step for the bearing race and maybe one more step down to the thread size.

I had to buy a giant die to thread the rod. I didn’t have handle for the die so I had to make that too. I found a steel pipe that the die fit in almost perfect. Drilled and tapped some holes for some “set screws.” Then I welded some rod to it for handles. Sorry for the blurry photos, they are screen shots from another Instagram video (@theroadhaus).

I ended up making the bottom diameter a little too small for a press fit. I showed it to my neighbor thinking it was ruined and I would have to start over. Then he took out a knurling tool and taught me a new trick. I knurled the end and that made it press in super tight. I made a little press for it with a pipe, threaded rod and some nuts.

Then I had to find new cups and bearings. They are a weird size so I had to combine two different bearing kits to get the right pieces. The Puch top race is the correct thread but the cups are too big at 31mm. The Vespa cups fit the frame perfect (30mm) but the top race is course thread instead of fine.

Another big part of the project was spacing the rear fender. It doesn’t sound like a tedious part but it kinda was. I made some spacers I welded to the fender so it could still be taken off pretty easily. I had to trim the front of the fender so it wouldn’t hit the Hobbit subframe. I might put a rubber mudflap between the fender and the subframe eventually.

I want this to be a long ride, possible motocamping rig so I have plans for a big sissybar/cargo rack. I started making the mounts in November of 2023. I had an extra piece of bent steel from when I made the rear shock mounts. I welded that under the seat so that, combined with the old shock mounts, became the rear rack mounts. Eventually I will weld a rack to these dog-bone brackets I made.

I messed up 3 of the bends on my first try of the sissy bar/cargo rack. I didn’t have any extra steel and kind of set the project aside for a full year. Then on Thanksgiving 2024 I took a few extra days off from work and finished the rack. The reason I didn’t assemble the rest of the bike without the rack was because I wanted to get all the welding out of the way first.

This time when I bent up the rack I only messed up the very last bend. So I decided to keep going and finish it. That was probably a mistake though because now the whole rack has a twist in it. Other than the twist, it turned out pretty good! Video on Instagram

This bike has a replacement full tank. The one that came with it had a huge hole in the bottom that someone (unsuccessfully) tried to repair with JB Weld. I got this used tank online. It is in pretty good condition but had some rust on the inside.

First I filled it up with some nuts and shook it around to break up all the rust inside. Then I degreased it with some Simple Green and a brush that attaches to my drill. I stuck a leaky air hose from my compressor into the tank to dry it out as quick as possible. Next filled it with Evaporust to dissolve the rust. I have done this process on pretty much all of my mopeds.

I let it soak for about 10 days and it came out perfectly clean.

Once the tank was clean I re-assembled everything. After sitting for 2.5 years, it started on the first rotation of the pedals!

Now that everything is assembled and running it’s time to take it all apart, Lol. I wanted to get the drivetrain to a point where it is comfortable cruising at 50mph and topping out around 60mph. I started with the rear gear box.

I took it apart, cleaned it up and washed out the old gear oil. I changed the big bearings, o-rings and seals but I left the needle bearings in. They spun smooth and are expensive and hard to change so I didn’t think it was worth it to change them, yet. There are videos of the disassembly and re-assembly on the @theroadhaus Instagram.

To disassemble you need the 24mm x 1.5 puller to remove the rear variator/pulley. I already had one for my Motobecane so I didn’t have to buy one specifically for the Hobbit. Splitting the cases was very easy, I just tapped them with a wooden mallet. I replaced the JIS hardware with allen bolts so it’s easy to disassemble in the future.

Next, I modified the rear vario. It has rivets inside that prevent it from closing all the way. If you remove the rivets and it closes all the way you will get better low end acceleration. You can see where the rivets were rubbing on the inside of the pulley in the photos.

The hardest part is splitting the pulleys. There is a 40mm x 1.5 puller but I didn’t have it. I just loosened the nut (27mm socket) almost all the way. Then I torched the outer pulley so it would expand and tapped the nut with a hammer until the cam popped up and hit the nut. Then took the nut off slowly because there is a spring inside.

It was super nasty and caked with old grease. I cleaned it all out and used a wire brush on my angle grinder to clean off the pulley faces. They were extremely pitted and rusty. After that I used my Dremel to grind off 3 rivet heads, popped out the rivets, then welded the holes shut.

Then I did the same to the next 3 rivets. I did 3 at a time so that the cam that the rivets are holding wouldn’t move out of place or fall out. Once the welding was done I put it on the lathe and shaved down the face so it would close fully. Video on Instagram

Before I tore the engine down I built a little stand for the frame. Video on Instagram.

The engine mostly came apart easily since I did some work on it to get it running 2 years prior. The hardest part was getting the stator plate off. It was so corroded it was seized to the cases. I actually had to use a puller to get it off the case, hopefully I didn’t bend it. Disassembly Video.

Steve said he thought it was soft seizing at the Black Pipes rally, I guess he was right!

I had to make a clutch puller. The actual clutch pullers range in price from $30-80. They have a dual function since they also remove the rear vario. As stated earlier, I already had that puller so it made more sense to just make a clutch puller. McMaster Carr is only a few minutes away from my shop so all I had to do was buy a $5 M24 nut.

I found a scrap piece of pipe, a nut and a bolt in my shop to weld together to make the puller. Video on Instagram.