MUTT

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Back in the summer of 2022, I picked up this 24 inch twin-tube Free Spirit frame along with 4 other bikes for free off of Facebook Marketplace.
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Out of all the frames I picked up that day, this one was easily my favorite of the bunch. I'm still not sure who manufactured it, though I want to say it was Murray. All I knew was that I hadn't seen too many of these types of frames before, and I had to have it.

For a while, I wasn't sure what I wanted to do with it, until I mocked up some 24"x2.125" tires on it and decided to make a 1980's-inspired BMX cruiser out of it.
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I had planned to enter it in the 2023 Annual Rat Rod Bikes Build Off as my first ever Class 2 build, as it'd be a good practice piece for welding a few gussets to the frame, but I had to pull the plug early on as I didn't have the funds to build the bike the way I wanted. You can see the original build thread for that here.
 
Fast forward to October 6th, 2023. I just picked up a few bike parts at a nearby swap meet for less than $30, including a pair of 24 inch wheels and the junior version of my childhood dream bike: the OCC Schwinn Sting Ray.
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Obviously, I'm too big to fit on the Sting Ray as it is, but I got the bike for the triple tree fork with the 1 inch threaded steerer tube, not necessarily the bike itself. I wasn't sure what bike I'd throw it on, but I knew they'd be good for something. I pulled the fork off, hoping to mock it up on something soon, or at least show it to @billn when I met up with him at the 2nd Annual Tulsa BMX Vintage Nationals Race, Show and Swap the next day.

While I was at the Tulsa BMX Vintage Nationals, I was on the hunt for some fresh inspiration for my stalled BMX build. I brought the Free Spirit frame and the loose triple tree fork to show @billn and see if he could give me some ideas for my bike. Up to that point, I was still thinking of making a 1980s-style BMX bike, but I felt I'd need to modify the dropouts to match the later BMX bikes, and spend a larger sum of money on parts, paint, and other materials to make it happen. Bill, who's way more familiar with BMX bikes, had another idea. He pointed out a number of BMX bikes at the show and inside the Museum that my frame and fork reminded him of, and that could be used as inspiration for my bike. Instead of shooting for a 1980s-inspired build, he suggested going for a much earlier 1970s-style build.

One of the first bikes Bill showed me was this 1975 Rink Raider, a bike that would soon evolve into the Torker. The 2 main reasons Bill pointed out this bike to me was for the way gussets were added to a twin-tube frame, and more importantly, the fact that the dropouts were the earlier, more traditional hook-style dropouts, as opposed to the later rear-slotted versions that's common on BMX bikes today. Bill suggested that I leave the dropouts on my frame as they are, as early '70s MX and BMX bikes had dropouts just like mine.
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The next bikes Bill highlighted for me were these Yamaha, Kawasaki, and other early BMX bikes that used triple tree forks. Some of them, like the 1975 Kawasaki pictured below, even used rigid triple tree forks with no built-in shock absorbers. Also worth noting is how a lot of these early BMX bikes still used banana or loaf seats.
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Even this little Mattel Vrroom Stallion had a triple tree fork!
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I don't know what bike this one below is, but the front gussets (and especially that fork setup) caught my eye!
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Even out in the swap meet and show, there were a few bikes that carried this new flavor I was craving for my bike. I've seen a number of 1970s bikes similar to this AMF MX bike that more closely match the dirt bikes of the day than the BMX bikes we know now, sporting a chain guard, fenders, a banana seat and sissy bar, and even a tank! These pre-BMX bikes had a lot more bulk to them than the BMX bikes that came later.
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Even this modified Sting Ray still carries most of its Muscle Bike roots while sporting a set of pegs and some mag wheels.
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After Bill's tour and my own browsing of the Vintage Nationals, I was charged up and ready to take this bike in a whole new direction!

Immediately after returning home, I slapped that triple tree fork on the frame, and fortunately, it actually fit the frame! The steerer tube would have been too short to fit most of my other bikes, but it fit this one just right. Still, I wasn't too sure about it, so I needed to mock up some more parts.
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On a later day, I mocked up a few more parts. First, I swapped out the previous seat for a banana seat and sissy bar, partly for the look, but mostly for a better seating position.
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Next, I found a chain guard from an AMF bike that could fit the frame with a little modification.
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Then I found a pair of ape hangers that just barely fit inside the 2 fork-mounted handlebar clamps. They might not stay, but I still feel they fit well enough. I also make a rough cardboard gusset for the front of the frame.
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The last part I mocked up was a front fender I could modify to fit the rear. And just like that, I found the look I was aiming for! This feels like those early BMX bikes that seemed more like an evolution of the muscle bikes that came before. Kind of fitting too, since I wanted to make this into a muscle bike before I chose to go the BMX route. In fact, I might pull triple duty with this bike; it's got a pair of slicks that would be great for the skate park, but I also have a fresh pair of 24" knobbies I could use for off-road rides, and if that's not enough, I even have a 1.75"-wide tire I could mount up front for a more muscular appearance! It's a triple threat!
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I did my usual digital mockup in Photoshop to see what the final look might be, and after weeks of tinkering with colors and graphics, I ultimately decided on this:
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Ideally, I'd like to run a black banana seat, but if that's not in the cards, I have a perfectly good black-and-white banana seat I could use instead.
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I plan to have Dad powder coat the bike in this super cool "Sparkle Granny Smith" color he has, with satin black and chrome accents to help break it up. Felt like a good color for a bike that's meant to be a transition between muscle bike and BMX.
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But why call a 24 inch Free Spirit 10-speed turned 1970s-era BMX cruiser "MUTT?" Well, there's 2 reasons for that.

1. This bike's a hodgepodge of different years, makes, and manufacturers of parts, and I don't quite know what even the main frame's supposed to be, just like how a "mutt" is made up of different dog breeds, including some that may be hard to identify. It's not one of the more "purist-type" bikes I'm used to seeing at the vintage BMX shows. This thing's cobbled together out of dirt-cheap parts I had on hand. In fact, the most expensive parts I have on this bike have got to be the 2 slick tires I currently have mocked up. Everything else I either got for free or close to it. So it's not a true period-correct build, but it is period-inspired.

2. "Mutt" is the name of a "character" from one of my favorite short-lived cartoons: Motorcity. "Mutt" is an amalgamation of 1970s muscle cars with a built-in escape chopper from the distant future that sports a flashy green paint job with black stripes. And like my plan for this bike, Motorcity's "Mutt" may look like a muscle car, but it has no problem forging its own path. I'd been itching to build a couple bikes as an homage to the show, and this would be a great one to start with!

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So far, this is where I'm at: a loose mockup and a dream. Good news is I should be able to make some serious progress on this bike soon. Unless something comes up, I'll be meeting up with my friend Allan sometime this weekend, who's going to teach me how to weld so I can weld the gussets to the frame myself.
 
Man, this is a contender already, and you haven't even started on color yet! Killer bones, I love that frame, and killer plan, Bill was right to look to the seventies for that frame and fork combo. I just have to highlight one bike from among all the beauties from your research trip, this one right here is a Gary Turner. Those initials would make a cool name for a bike company. The historical importance of that bike can't be overstated
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As a kid I always thought the Mattel Vrroom bile was cool. With it's large tires, over sized fenders and fake engine, it was a heavy slow bike. One kid in the hood had the bike, sure did ride smooth!

Later Mattel brought out the Stallion. It was also available in red. Striped down as pictured, much lighter than the original. I don't think there were many sold.
 
Man, this is a contender already, and you haven't even started on color yet! Killer bones, I love that frame, and killer plan, Bill was right to look to the seventies for that frame and fork combo. I just have to highlight one bike from among all the beauties from your research trip, this one right here is a Gary Turner. Those initials would make a cool name for a bike company. The historical importance of that bike can't be overstatedView attachment 255832
Thanks! @billn was really the one who introduced me to the world of vintage BMX, so I knew his advice would be super helpful in building my first BMX bike.

Yeah, I thought that bike looked familiar to me, then I remembered Rat Rod shared a video about the Gary Turner Monoshock back in 2020!
 
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As a kid I always thought the Mattel Vrroom bile was cool. With it's large tires, over sized fenders and fake engine, it was a heavy slow bike. One kid in the hood had the bike, sure did ride smooth!

Later Mattel brought out the Stallion. It was also available in red. Striped down as pictured, much lighter than the original. I don't think there were many sold.
I felt the same way when I first saw the OCC Sting Ray as a kid; I had never seen bicycle tires that wide before, nor a bike that looked so much like an actual chopper! They may not have been the fastest bikes, but that's never stopped me from wanting one of my own!

I actually have a working Vrroom motor that would have been attached to that bike! I've currently got it mocked up on another project of mine at the moment. I just love how that Vrroom bike almost perfectly mimics a mini/pit bike!
 
Got a small update for today. I did a few more mockups on Mutt today before I started loading up everything I'd need to work on my bikes at my friend Allan's place tomorrow. I liked everything I had mocked up on the bike so far, but one thing that started bugging me was the chainring. It looked great when I was going for an '80s BMX vibe, but now that I was going for a '70s MX vibe, it just felt too new. I decided to see what a leftover Schwinn mag chainring would look like on it, and I like this much better. Plus it kind of reminds me of the original chainring that came with this bike; it had a 5-spoke guard similar to this chainring. I also mocked up the only black banana seat I currently have in my inventory, just to see how it'd look.
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I might be able to get away with using this seat if I slap a few stickers over the tears in the seat, but I'd rather just use either a more intact seat or reupholster this one. I already have some black leather I was going to use on another banana seat, so this might be a good time to learn a new skill.
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I also mocked up the other 24 inch tires I had on hand. First, I mocked up the "muscle bike" look with a 1.75"-wide front, and a 2.125"-wide rear, which I think looks pretty good.
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Next I mocked up the knobby off road tires I just got from another freebie bike, and WOW! I was not expecting to like this look as much as I do! Now it really looks like those early MX bikes!
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The wheels aren't perfectly true, but there's just enough clearance in the frame for the knobbies!
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A closer look at the tread on the 1.75" tire and the 2.125" slicks. Not what I'd prefer for this style of bike, but I bought them for a different project years ago, and since they aren't going on that bike, I may as well use them on this one!
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I also mocked up my good black-on-white banana seat as well. I like it, but I won't know for sure until I get this bike powder coated.
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One last thing I toyed around with was a set of handlebars that had more of a BMX look. They fit the bill, but they feel just a little too short for my liking, compared to those tall ape hangers I had on earlier. Kind of funny, since these are the tallest BMX bars I've got. Still, if push comes to shove, I can go back to those ape hangers or learn how to make my own out of the materials I have on hand.
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Tomorrow will hopefully have a very big update, with some custom gussets welded to the frame and a few other modifications! Stay tuned!
 
Got a small update for today. I did a few more mockups on Mutt today before I started loading up everything I'd need to work on my bikes at my friend Allan's place tomorrow. I liked everything I had mocked up on the bike so far, but one thing that started bugging me was the chainring. It looked great when I was going for an '80s BMX vibe, but now that I was going for a '70s MX vibe, it just felt too new. I decided to see what a leftover Schwinn mag chainring would look like on it, and I like this much better. Plus it kind of reminds me of the original chainring that came with this bike; it had a 5-spoke guard similar to this chainring. I also mocked up the only black banana seat I currently have in my inventory, just to see how it'd look.
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I might be able to get away with using this seat if I slap a few stickers over the tears in the seat, but I'd rather just use either a more intact seat or reupholster this one. I already have some black leather I was going to use on another banana seat, so this might be a good time to learn a new skill.
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I also mocked up the other 24 inch tires I had on hand. First, I mocked up the "muscle bike" look with a 1.75"-wide front, and a 2.125"-wide rear, which I think looks pretty good.
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Next I mocked up the knobby off road tires I just got from another freebie bike, and WOW! I was not expecting to like this look as much as I do! Now it really looks like those early MX bikes!
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The wheels aren't perfectly true, but there's just enough clearance in the frame for the knobbies!
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A closer look at the tread on the 1.75" tire and the 2.125" slicks. Not what I'd prefer for this style of bike, but I bought them for a different project years ago, and since they aren't going on that bike, I may as well use them on this one!
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I also mocked up my good black-on-white banana seat as well. I like it, but I won't know for sure until I get this bike powder coated.
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One last thing I toyed around with was a set of handlebars that had more of a BMX look. They fit the bill, but they feel just a little too short for my liking, compared to those tall ape hangers I had on earlier. Kind of funny, since these are the tallest BMX bars I've got. Still, if push comes to shove, I can go back to those ape hangers or learn how to make my own out of the materials I have on hand.
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Tomorrow will hopefully have a very big update, with some custom gussets welded to the frame and a few other modifications! Stay tuned!
Looking good! I really like the knobby tires on this one. Those BMX bars might look better if you could build some risers for the handlbar clamps. That could get them up taller without having to build new bars.
 
Great video, thanks for posting it! If I had the time and skills it would be fun to build a tribute to one of these.
You're welcome! It would be fun to build a custom full suspension bike like that.
Looking good! I really like the knobby tires on this one. Those BMX bars might look better if you could build some risers for the handlbar clamps. That could get them up taller without having to build new bars.
Thanks! Not sure how I'd make a set of risers for this type of fork, but I have a few ideas of how I could make my own handlebars. I'm not too worried about it right now though.
 
I really like this twin tube frame! Knobby tires look good, too; IMO. Definitely gonna keep an eye on this one.
I love twin tube frames myself. I was genuinely surprised by how good the knobby tires looked on this bike. I'm not really an "off-road" kind of guy, at least when it comes to bicycles, but this bike just might convert me. Thanks!
 
BIG UPDATE!

On Sunday, I met up with my friend Allan and got to work on the heavy fabrication needed to transform Mutt into a BMX bike. I figured it'd all go by quickly, and we'd have enough time to make a little extra progress on another bike of mine, but things didn't pan out at all like I expected.

First, I needed to redesign my gusset template, as the previous one was too large. Once that was done, Allan and I needed to test out my dad's 1 1/2" hole saw for this idea I had for the hole in the gussets. Turns out that not only was the hole saw not perfectly round and slightly larger than 1 1/2 inches, but the center drill bit was crooked as well. Fortunately, we were able to adjust the hole saw with a hammer to the diameter we needed, and Allan had plenty of drill bits to replace the crooked one. UNfortunately, most of the drill bits he swapped into the hole say either became crooked themselves, or they BROKE entirely! I think we went through at least 8 different bits in at least an hour before we could finally drill a good 1 1/2 inch-diameter hole consistently.
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Once the hole saw problem was sorted out, Allan suggested cutting the holes out of the scrap steel plate I had before cutting the gussets out themselves. So we lined up the carboard template with a hole as best as we could, taped it to the metal, and then Allan cut along the template with a cutoff wheel.
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Then he used the first cut gusset as his template for the next one.
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Allan then showed me how to use the "soft wheel" as he calls it, and I ground the 2 gussets to a nice, smooth finish. Got to say, I was pretty nervous using this tool at first. I'm always a bit hesitant to use tools that I have next to no experience with, especially when I know I can get seriously hurt by them, but after a few passes with the soft wheel, I managed to get a lot more comfortable using it. Got to say, I'm pretty proud of how I did my first time around!
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This is the part where I have to confess something: My original plan was to learn how to weld on this bike by welding the gussets to the frame myself. Unfortunately, I did not do well on my practice pieces at all this time, and I sheepishly chickened out of welding on the bike itself. I pretty much learned that day that I can hold just about anything steady except for my own two hands. Kind of critical when you're trying to avoid melting a hole though steel. Welding is an artform, but unlike working with pencil and paper or the pen tool in Photoshop, there's no eraser to clean up your mistakes.

That said, I can still say I welded on some parts of the bike! Admittedly, all I did were a few tack welds to the gussets, and Allan still had to add a little more to some of them, but I'm still pretty happy with the results!

This is where I reveal my favorite part of my whole plan for these gussets. I didn't want the gussets to be just two flat plates with a simple hole drilled through them; I wanted to make these gussets look dimple-died like a factory piece. Problem is, neither Allan nor I have a dimple die tool, but I had two Schwinn fork races that were too rough to use for their original purpose, and they both were almost the same width as my scrap plate of steel!
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Turns out the underside of those old Schwinn races have a really nice shape that feels like a dimple-died hole!
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Allan had an idea to hid most of the welds that held the gussets to the frame on the inside, with only the front-most welds being visible on the outside.
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Allan also came up with the idea of using one of the drilled-out holes as a tab to mount the chain guard to the frame. Originally, I had planned to weld a couple gussets to the dropouts, but after the hassle of making and installing the 2 main gussets at the front of the frame, and because it was getting late, I figured a simple tab would do. Besides, some of those early 70s BMX bikes didn't have rear gussets either, so it'll still look "period-correct."
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After all the welding was done, Allan helped me adjust and trim the fender and chain guard to fit the frame, and I reassembled Mutt to get a better look. It could still use a bit of refinement, but overall, I'm happy with the progress we made on Sunday! I may not have learned as much about welding as I had hoped, (other than I'm really bad at it,) but I still got to learn how to use a tool I never messed with before, and it's not like I can't do more work on the bike myself!
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Once I brought Mutt home, I got some better pictures of the work that had been done.
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I'll need to do some sanding and filing to clean up everything, and the chain guard needs adjustments, but overall, I'm happy with the end result. That said, I feel like some of the work could use body filler before I get the frame power coated. Does anyone know of some good powder coat-safe metallized filler I could get in small, inexpensive quantities? I may not be cut out for welding, but maybe I could fare better in body work.
 
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Great looking frame already. Those gussets are a cool edition.

I've seen tall handlebar mounts that would bolt to those schwinn triple tree forks. They came on some of the electric mini bikes that were around about 5 years ago.
 
Great looking frame already. Those gussets are a cool edition.

I've seen tall handlebar mounts that would bolt to those schwinn triple tree forks. They came on some of the electric mini bikes that were around about 5 years ago.
Thanks!

I just took a look at some online. Definitely a neat idea, but I think I'll just work with what I have for now. I'll keep it in mind for down the road though!
 
It really is a interesting frame, off-road/road racer. It could fit in both builds.
It's a mixer...
 

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