Topic: Throw out your "cafe line diagrams" cb550 bobber!

[work9to5]

Ok so the short of it. Building a cb550 into a Bobber , have run into an issue. The frame tank mounts have got to go. Not just the tab that the rubber boot would fit over but the whole round area as it gets in the way of the tank I'm fitting on. Anyone have ideas on how to do this the best way? Here are the options I can think of-

1. Use a hole saw and drill clear through the frame. Then weld a patch over

2. Take a hammer and nock the circular form down a bit

3. Try widening the tunnel of the tank. Use a "backwards" clamp and pry the tunnel a bit

I think #1 sounds like the best option but also the most work. How would you guys do it? #2 sounds too easy, but tempting. #3 do I really want to bend a brand new awesome tank? Would it bend/open enough without causing flex in other areas? How would you guys do it? Ideas appreciated.

[calj737]

Of the options you listed, #1 and only #1.
#2 will weaken the area and be primitive in the result.
#3 will damage your tank.

OR, #4:

Use a bandsaw and cut the top tube/neck free. Shorten the top tube, slug a new section of straight tube in to replace the gusseted area. Weld back to the neck.

How does your new tank paling/mount at the front if there are no C-clips to fit over the rubber stops?

[work9to5]

I had considered the 4th option as well. But really love the curved stamped frame of the cb. Without it, it would look too much like an xs frame.

As far as mounts for the tank. I'm going to weld on two small tabs onto the tank and go through the frame with a bolt. The tabs currently on the tank will have to go.

I'll do a build thread once she starts looking like something. Which will happen quickly as I have almost all the intended parts on hand. And for all you purists out there, this bike was all separate piece (motor/frame)purchases. I'm not ruining a beautiful original to do this one.

[MCRider]

I'm no machinist but...

Could you take an angle grinder and just have at it? You'd have more control of where you end up. After cutting the peg off, probably wouldn't take 20 minutes to grind it down to size.

[Camrector]

Option #5: quit building bobbers!

  Love you Chris

[work9to5]

I think the issue with that is uniformity. I'll end up with a "not so round hole" and patching it with a weld would be harder.

[work9to5]

As far as option 5. I own a cafe 550 and a tracker'ish 550, I wanted to round out the garage with a bobber   And honestly a lot of the stuff I'm planning has never been done to a cb. I wanted a challenge. the plan is to not build something that is garage hacked bobber looking. I'm not just throwing it together. I've put allot of thought into what will work with this platform.

[calj737]

Option 4 doesn't require a change to the sloped top tube. Only a slight section about 4" from neck back.

I don't know what you're considering, but "it's all been done before" to a large extent. Just do whatever you're intending well and anyone will appreciate and admire it. 

[work9to5]

Just noticed that was you that posted that Cam!

Calj, that actually hadn't occurred to me! Exactly why I asked for opinions. I misunderstood what you where suggesting with #4. Yeah, that could definitely be an option.

[754]

I would grind off the flat part and peg, then work what is left , into the hole, so therevis lits of meat and easier  to weld to.
 Now the back probably need to cut out them dual petcock bungs, toss them..British junk 19 tip stuff .
Mount and 1/4 or 3/8 NPT bung , more petcock choices.

[work9to5]

754, that's exactly what I think I'm gonna end up doing. Going to use a stepped drill bit tho to try to keep the whole a bit uniform. Depending on how the hole comes out (diameter) i may be able to put 2" of round bar in there to plug it.

I was actually excited about the dual petcocks in the back. Depending on how the tank sits I thought they would look trick. They would be feeding a dual intake PD carb. I could just use the bottom 3/8 bung though. Part of my inspiration for this is a blurry pic of a bobbed up bsa. What's your grudge with em? Don't get enough flow?

[754]

They care a British thread, maybe BSP. Not a huge petcock choice, but if they clear the frame use them.
I like to see the tank right down close to the frame looks bad otherwise. I would run rubber washer between  tank and frame, at the mount points .
 I used to use the rubersvthey used on exhaust hangers.

[work9to5]

Got the mount tabs shaved off this morning. I was actually able to get the tank in place after removing the pegs. It fits so snugly that it was actually hard to remove. Next de-tabbed the tank and it sits just the way I wanted it. Going to cut up a bolt and weld and shave it off to fit the hole. Unfortunately the coils will not fit in the stock location with this tank. Something I was aware of an have an idea for, but ideas are welcome.

Next hurdle is the kickstand. The left exhaust interferes with the spring and it has to change somehow. I have no idea what I'm going to do yet and ideas are extremely welcome. Possible options I can think of-

1.) there may be another factory stock stand from a different model that would fit the cb's mount?

2.) weld in a "bobber" style kickstand that is not spring actuated.

#1 would be a hell of a lot easier. But style wise I guess I could use an upgrade. The only problem I may have with #2 is that I'm only mig capable. Is this something that absolutely has to be done with tig or will mig cut it? Ideas welcome as always!

Pics are of as she sits today and a pic of the exhaust/stand. I'm planning drag long pipesso the situation will be exasperated. She looks a little funky fender is on the way and should even her out a bit. I think the seat fits with the style I'm going towards. But may go with something slimmer. Gonna wait till I see how the fender sits. Bars may change who knows lol

[work9to5]

Pics

[754]

Not sure it works on a 550 but I have mounted coils under the carbs with extended wires . Ran the wires thru the cylinder fins near the middle of the engine, and up to the plugs.  Use 7mm silicone wire.

[work9to5]

754, got something crazier than that planned for their location lol.

[calj737]

MIG works fine if you know what you're doing. Tube is 0.063 thin so it won't take much heat. But make sure you do get the weld burned in sufficiently.

[work9to5]

Ok, thanks for the info on the tube thickness. 👍

[work9to5]

Some progress. Rear fender came in. Chopped it to fit. The bike is starting to look how I wanted it in my minds eye. Had to throw on a different set of bars because the scrambler bars where throwing me off a bit. Tho I wasn't thinking I was going to use them the clubmans look pretty good on her. My garage is a bit cramped with other projects so not the best pics but I think you can see where I'm going with it finally.

Modifying the shrouds today. And mocking the wiring to see how it'll lay on the frame as well. Maybe I'll roll her to the curb for a better pic after. Input appreciated

[work9to5]

It's funky to say the least. I think powder will bring it more together, make your eye run over her smoother but that is a bunch of steps away. Also cutting a plate to weld into the under cariage of the fender to mount the rear light all "hidden" like. I've got another build thread going on cb550 hoop job going as well and will be tacking that up today.