Turd Ferguson CB450 Hardtail Bobber

[spidergsgp]

I've had my 450 for 2 years now and it's time for something new. I've had the cylinders bored to 73.5 making it close to 500cc. It's a mean bike and needs a hard tail. Please keep in mind I have no idea what I'm doing and am not planning on doing the welding on the bike. I'm going to mock it up and take it to a professional. Here are some pictures of the progress so far.

$200 not running and covered in mud. If mud could get packed in somewhere, it was. 16" rear wheel and chrome swingarm.

I cleaned the tank and carbs and got it running sort of. Tore the engine down and found tons of metal everywhere. Ended up boring the cylinders, replacing the cams and all end caps/bearings.


Here's my daughter helping with the teardown.

This is how I rode it last summer. It was pretty freaking loud. ....and then I blew the headgasket and started blowing oil out of the right cylinder.

I started chopping today!

first mockup I cut up my chaparral frame to get ideas for bends

I'm not too happy with those bends. I might use some conduit to mock up and have someone bend the pipe for me. I'm planning to run the rails and cut the swingarm out. That's a 360 swing arm to gain a little length too.

 

[spidergsgp]

Got the top arms on today, I still wish it were 10 degrees warmer out. I'm still finding mud tucked in the corners of the frame.

Some of my supplies came in too. All-Balls bearing set, old school light switch, horn button and dust boots. Once my fork seals come in I can start putting the front end together. I also have a copper head gasket in the works so I don't blow anymore oil out of the exhaust.

I'll be using this tank too, it was more than I wanted to spend so hopefully it looks cool!

 

[uncletwisty]

titties.. whats the tank from?

 

[troybilt]

I really like the tank and if you can get the rest of the bike to look half as good as the motor wow. It really looks fantastic. Anyhow, you mentioned picking up some pipe to replace the whats there. My concern about what's there is not only ascetic but also there is no place for energy to dissipate as it travels from the axle plate up the seat rail. Normally it should travel on to the rest of the frame. With those sharp bends and without major gusseting and bracing it could be a place for catastrophic failure.
I would also have to assume that with limited energy dissipation the ride would comfort would also be greatly affected.
I would recommend picking up some 1 1/8" .120 wall dom tubing. Also pick up something that you can use as a slug to go inside the mating pieces. It should be rosette welded making sure to get good penetration. Hope you don't mind. Just thought I'd offer some help.

 

[VonYinzer]

Couple points...
-Your swinger isnt paralell to the ground. Its pointing down, which will lift the back of the bike way up in the air. Remember that the end of the swinger is where the center of your rear wheel will be.
-The swinger isnt long enough. You should have around 4+ inches of stretch to keep the geometry kosher.
-You should use your rear wheel/tire to mock up the frame. Itll give you the proper angles.

Thats about it. Look up the 450 bobber that Dime City cycles built. Itll give you a good idea of where to go with yours.

Keep us posted man.

 

[troybilt]

Vonyinzer has some very good points. A stretch out the back would give a little more forgiving angles on the seat rails. One thing to help achieve that during mock up/jig phase is to relocate the swinger to the passenger pegs. Would be ok to do since you mention plans to add the bottom rails and cutting the swinger out. Smart choice btw. Anyhow, good luck and like Mike said keep us posted

 

[VonYinzer]

That motor is dead sexy by the way...

 

[spidergsgp]

The tank is from a Sprint 350


So you guys are saying I'll need to cut it up again before I take it to the welder...damn. I was really hoping to cheat and not have to stretch the bike. I ran all the pipe at least 2" into the existing frame tubing. I drilled holes throughout and welded through. I also welded the pipes together and slide a collar(to be welded not by me) over the down-bent joint. I'll take some better pictures tomorrow.

 

[spidergsgp]

mock up please ignore my ugly welds, they're getting ground down before going to the welder. I still need to add gussets but it's looking cool and coming along nicely. There's still some cutting to do on the old frame section as well.

got another shipment of parts today...still no camchain, head gasket or fork seals...

 

[VonYinzer]

Im sorry man, but that isnt safe. Not only that, but how do you plan on mounting a seat to that frame? Im honestly not trying to give you shit. Just dont want to see anyone hurt. That is all. Ill leave you alone now.

 

[VonYinzer]

http://www.dotheton.com/forum/index.php?topic=12664.0

 

[spidergsgp]

Im sorry man, but that isnt safe. Not only that, but how do you plan on mounting a seat to that frame? Im honestly not trying to give you shit. Just dont want to see anyone hurt. That is all. Ill leave you alone now.

The frame isn't safe or the geometry isn't safe? I extended it 3" and lowered it 1.5" It's pretty much the same as adding the hard "struts" as shock replacements that they sell as hardtail lowering kits. Please tell me if i'm there's something I'm not getting.

 

[VonYinzer]

Maybe its the angle of the pics... But that looks like you lowered it WAY more than 1.5". When you hardtail a frame, you need to set the ride height from the center of the motor cradle. Than, set the axle plates in place. The easiest way to do this without a jig is by using the rear wheel. From the pic it looks like your rear axle is about 1 - 2 inches above your lowest point on the bike. That is way off.

 

[VonYinzer]

Heres a great example of a pretty common style of chopper frame.

Notice how much higher the axle plates are on that bike? And the smooth transition from backbone to the top of said axle plates?

That link I posted earlier has a TON of info on the correct geometry of a frame. Take a sec and go through it, and Im sure youll get what Im saying a bit more clearly. Im not great at explaining things.

The way Im seeing your frame, the entire thing will be pointed down at the ground. Youll have nearly no rake and therefore the frame is useless. Before you go any further, just do me a favor. Mount the forks and wheels and take a profile shot so I can see where you are now. We'll get ya straightened out with where everything needs to be.

Another issue is the actual material youre using... Look in that link again and read up on proper tubing for frame work and how to correctly join the tubing together. You've actually created some pretty weak points in how you've connected everything.

In the end, building a frame (or a bike in general) is all about planning it out. Ask me how I know what happens when you rush... Its a real measure 25x and than 25 more, than cut kinda deal.

Theres plenty of the original frame left to get you headed in the right direction though.

 

[VonYinzer]

Oh, and one more thing... Youll want to get some actual axle plates cut out. Like these:

And notch and weld the frame so it is supporting the plates from both sides like this:

You can have any fab shop make you some plates for very little money. Just make sure they are identical.

If you have no local metal fabriction joints, you can buy pre-made units as well. Just make sure that they are cut for the correct axle size.

TCBros choppers should have what you need, and if not Im sure theyll make them.

 

[spidergsgp]

here's how she's sitting now. 32 degrees rake, 4" of trail and about 5" off the ground at the bottom rails. I'm gonna do some research and get back to this one. If it's decent I'll probably just ride it. I'm sure this won't be the first hardtail I make.

 

[uncletwisty]

we're riding this this weekend.

 

[spidergsgp]

how many bikes can you ride down?

 

[spidergsgp]

Von- I understand exactly what you're saying now. Mine is close to the correct ride height(still seems a little low) but the structure is ass backwards. I should have cut more into the top and ran that pipe straight while putting a bend on the lower pipe. I did the opposite and it doesn't send an impact through very well. Like everything else, failure is the best instructor. I think the tubing will hold for the kind of riding I plan to do, my Triumph is still going to be my all the time ride. Now the question is...do I ride it until it drives me nuts(which it will) or fix it now?


I wish there were still companies like this.

On the other progress.. My fork seals finally came in, 37 year old seals are hell to get out! I'd rather do any of the seals that I dread at work than those suckers. It's really hard to get them out and not scratch or gouge anything. I even tried a screw attached to a small slide hammer, which didn't work. I had to tap around the edge of the seal to loosen in, knock a hole in the metal, and pry out while trying to avoid damaging anything.

 

[VonYinzer]

Cool man. Im glad you didnt think I was giving you shit. Just want to help you get it done right. I still have to say though, get the best material you can. Its pretty cheap, and your life depends on it. Even at 30mph, if that frame fails... Terrible things can happen.