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Discussion Starter #1
As everyone in RT knows, I've been working on a bobber project for about a week now. It was a bit of a spontaneous decision brought on by happening across a picture of a hard tail gs750 last week.

It just so happens, I have a gs750.

Backstory:

When I was a kid my dad always had so much cool stuff. He had a 3rd gen camaro, we watched nascar, he had a big truck, and he had a 1977 gs750. I don't think I ever even got to ride in the camaro before it was sold. The truck I always thought was cool but it was too tall for me to get in (in hindsight, I was just a little kid and it isn't that big). The bike always fascinated me. It was so loud I was afraid to be outside when he started it. It had a red tank. It was the coolest thing ever.

He started riding me around on the gas tank when I was too little to hold on. We'd do laps in the yard. Eventually I got to do some rides out on the road. Then in 2003, when I was 13, he got into an accident on the bike. A dude who was all doped up ran a light and hit him from the side. The bike was dead, and he went a couple years without one.

He kept it though, because he's a bit of a pack rat and keeps everything. So I decided a long time ago I was going to fix it up. The damage from the accident was unclear, but something somewhere was bent. Due to a lack of skill and money I never really tackled the project. Then about five years ago I decided it was time. We threw it in my truck and brought it to my house. I ripped some stuff off of the back, confirmed something was indeed bent, and ran out of time and motivation.

Enter this image..



That hit me pretty good. I loved it immediately. My buddy has a bobber and we've talked about them, but I never had any intention of owning one. Seeing that lit a fire though. A ton of research on bobbers, using the oem swingarm like in that picture, hardtails in general, etc all came pretty quick. I looked at hundreds of them for inspiration. I yanked the bike out of the garage and rolled it into my shop and started unbolting literally everything I could see. You can see the progress of that below.

My dad showed up by chance like day 2 and helped me for a few hours. When it came time to pull the engine we couldn't seem to pick it up at the right angle to get it out of the frame, so I decided we'd just hold the engine in the frame and tip the whole bike over. Slipped right out. Excellent.

Since then I've finished stripping it as you can see. I've lowered the front about 2.5 inches, lowered the rear about 4-5" and tack welded a rod to the swingarm and the subframe that's getting removed to keep the height fixed. Next step is to weld a square tube to the two crossbars that are clamped to the frame. That single tube will act as a receiver for a telescoping tube with a vertical piece that'll hold a temporary axle right in the oem axle plates. Then I'll remove the swingarm and cut the subframe off, machine new axle plates, and build my hard tail around the new axle plates mounted to the temporary axle.

End result will have clipons, be blacked out minus the tank which will be a sand/tan type color, and should have the exact stance of the last image. I'll be doing a bit of machining here and there which I'll post up as it happens. Not much going on so far, but it was recommended I make a thread, so. I made a thread.
 

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Discussion Starter #4
My calc 2 class was canceled last night and my wife wanted to nap, so I spend some time yesterday getting some work done on this.

I welded (poorly) the main part of the jig to the bottom of the two cross bars after drilling and tapping it for two bolts to keep everything tight. Then I took the front end off, and the rear tire. Cut the vertical piece but haven't welded it yet. Took all of my measurements to make my axle plates and came up with a plan there. I need to order an end mill later so I can get those started, and I need to find a bar/pipe/tube that fits in the axle plate, or have one turned down.

I also need to add a horizontal bar at the front of the jig to keep things from tipping over.

Not terrible so far. I definitely need some welding practice though. It's been a while.
 

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Discussion Starter #6
Kinda stalled out for the moment unfortunately. A family birthday party, the wife wanting to go to the beach, and my track day got me a little behind on things. I'll be getting back into it this weekend though. Friday evening I'm hoping to come up with a plan for the bending. What I'm thinking is using a steel wheel to bend around, with the sand bending method. I need to make four bends so we'll see how it goes. I guess it's a little easier on heavier wall tube, and this is pretty hefty stuff.

I picked up a ton of jb weld, like 10oz, to fill in the pockets on the bottom of the upper triple clamp. Then I can mill it down without putting holes in it. Other option is a 120+ dollar billet one and that sucks. So we'll try this first.

I'm also even lower than I was when I made the first post. The forks are sticking out way too much and it looks dumb. I'll be lowering the front internally so I can move the tubes back down ~2" in the triples. Then with the clipons on top it'll look fine.

Oh and I ordered 7* vortex clipons
 

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Discussion Starter #8
Dude...don't feel bad. Look how old my "build" thread is :lol:
I just want to work on it so bad lol. I was planning on doing a lot this weekend.. but apparently I'm going to a show after work friday with my wife, then she decided to take saturday off so there goes that. I'll get sunday at least.

She wouldn't mind if I worked on it when she's home, but with our schedules we never see each other for more than like an hour a day. So I wanna take that time and spend it with her instead.

Sunday is a bobber day tho. Updates coming next week.
 

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Mufasa in Training
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She wouldn't mind if I worked on it when she's home, but with our schedules we never see each other for more than like an hour a day. So I wanna take that time and spend it with her instead.
You have my sympathies! If I'm not at work, I pretty much expect that I'm spending time with my wife, kids (if I'm trying to give my wife some peace and quiet), or both. I just feel bad about saying "welp, see you guys later" and disappearing into the garage only to return when I manage to break something else :lol:
 

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Woo. Updatez.

My wife wanted to get to bed early Saturday evening, so I went out to the shop to try to make some progress on my cb360. Quickly determined the battery is too beat to start it, even with the kick.. so I abandoned that in favor of bobber things.

I decided I was determined to find/make a temp axle rather than wait to use a friend's lathe. I grabbed every piece of pipe and round scrap I could find until I found an old galvanized pipe that was close to the right diameter. I used my belt grinder and got it to a workable diameter and also took the coating off of the area I'd need to weld. I also popped my axle plate stock into the bridgeport and milled it to the correct thickness, then called it for the night.

The next morning was rainy and I felt pretty lazy. Decided I needed to do something though so I went over and looked things over. Decided it would be cool to get the swingarm off which meant finishing the jig, so I started on that. Used the belt grinder to get the vertical piece close in height then I filed the rest of it in. Popped everything into the right place and welded it up. It looks a little goofed and crooked, but the axle is perfectly straight and right where it belongs which is the only thing that matters. I'll never use this jig again and I'll just be cutting it apart after to be used for something else someday.

With that done I got to cut a bunch of junk off which was cool.

One of the next steps is making the axle plates. I ordered the 13/16 endmill I needed (got a ball end because it just happened to be the cheapest). None of my endmills will plunge, so after marking out the location of the slot and lining up my y axis in the middle I just drilled through. Then plunged with a 3/8" endmill since the lack of cutting edge in the middle didn't matter. Then I just milled the slot in .100 increments. Then I did basically the same with a 3/4". The 13/16 I plunged full depth and did the slot in one pass for uniformity. Came out great and the oem tensioner fits, so we're good!

Next steps include coming up with the axle plate design and cutting them apart/shaping them, figuring out exactly how I'm cutting the stock frame to add my new tube, and bends.

Uploads aren't working right for me so here's a flicker album with a few pics https://flic.kr/s/aHsmEFvESE
 

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Discussion Starter #14
I couldn't imagine making my own axle :eek:

I don't trust my own wrench-work, much less something as specialized as lathe and welding.
It's just a placeholder. It's the same diameter as the oem axle, so I can put it inside of the stock axle plates and then weld it to the jig. It'll hold the location of the axle plates I am making. Then I can weld new frame to the axle plates which I'll just tack to the temporary axle. Once I'm done the rear wheel/axle assembly will be 100% oem, but it'll be inside new custom plates.
 

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Mufasa in Training
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It's just a placeholder. It's the same diameter as the oem axle, so I can put it inside of the stock axle plates and then weld it to the jig. It'll hold the location of the axle plates I am making. Then I can weld new frame to the axle plates which I'll just tack to the temporary axle. Once I'm done the rear wheel/axle assembly will be 100% oem, but it'll be inside new custom plates.
You're way over my ability level :lol:
 

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HEY GUYS I DID A THING

I was thinking about paying a shop to do my bends just to save myself the embarrassment of messing them up, and the time it takes to mess them up. I did order enough material that I could screw it up once though, and after spending the money on the miata I decided to try to save some here.

Man am I glad I did. The bends came out awesome and it's gonna be neat to be able to say "I built that".

I spot welded plates to the end of each tube to block them off, but not seal them in case there was moisture in the sand which created steam. I used 6-8 spots per plate. Then filled with sand, pound sand down with hammer, fill, repeat until you can't compress it anymore. Then I cut a tight wooden dowel for each and pounded that in until it stopped, plugging both ends.

As for the actual bending, I had considered making a whole jig type thing that would give me some easy repeatability, but in the end I did the farmer thing and bolted an old wheel to the drawbar of a tractor. I bent around the wheel and wedged the end of the tube into the tractor. You can kinda see in the first pic.

So I'd stick the tube in there and put the other end on a chair (pulled away from the wheel obv) and heated with a rosebud. Once it was nice and hot I'd shut the torch down quick and grab the bar, make sure it was locked into place and bend it looking down for a mark I had on the floor to approximate where to stop. The first two come out great, the second two I had to bend a bit further/tweak. Honestly though, I think they came out amazing. It saved me 150 bucks and it was a lot of fun. Easily one of the coolest things I've ever done.

Everything mocked up pretty good so next step is going to be clamping these into place while I come up with the final shape for the axle plates and get those ready. Then I'll be cutting into the frame next to actually add the hard tail!
 

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Progress stalled out on this while I was waiting for some parts to be machined. They were finished last weekend, and, after careful consideration... I'm not even using them lol.

The parts are plugs that bridge the gap between the old tube and the new tube. This adds strength.. but the tube I'm using to extend the frame is actually only slightly bigger than the ID of the old frame. The difference is small enough that if I hit the tube I have on a belt grinder for a few second it'll fit. So I'm just going to slip that in about 6", plug weld it, and then weld the seam where they overlap. It'll be plenty strong, lighter, and easier.

So I started working on the hole for the hard tail tube to slip into the frame. I've been grinding it out and filing to open up the hole. There were two obstacles in my way.

One, there is a seam inside of the tube. I went out of my way to get DOM, apparently suzuki didn't. I used a die grinder to reach in and remove that.

Two, there are indents in the frame tube. You'll see that in the first picture. It's about 3" long on the outside edge of the frame on both sides. I think it may be for strength but I'm not a mechanical engineer so I can say for sure. With the .120 wall tubing I'm slipping through there strength won't be an issue though, so this needed to go. I considered cutting it out, trying to pull it, drilling on the back side and punching it out etc. I ended up finding a conveniently sized pin with a taper on it. I pounded it in with a hammer and it's pretty much straight now.. but it was stuck. Some quick DIY slide hammer innovation got it back out though. I'm going to cut the rod off of it and do it again on the other side.

Anyway, the tubing just about fits. It'll need a little tweaking to get it to sit straight but we're in good shape so far. Feels good to have that piece fit in there like it does. Once I get the other side done I'll trim my tube and get it welded up!

edit - pics are backwards. The last and first should be reversed. In the last it looks like the indent is more prominent than it really is due to lighting
 

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