New CB350 Project - Back Breaker

dynamitedave

dcclassiccycles.com
I picked up a pile of shit CB350 from a motorcycle yard sale guy for next to nothing. I really just needed the engine.

I'm running out of styles for CB350s so it took me a little while to figure out the direction I wanted to go.

I cut it up, lowered it, hard tailed it. I plan to recess the seat and have a low gas tank. Might have to make my own or cut up and reweld one I have laying around.

This is what I started with. You can see how much I lowered it in the front by the fork tubes sticking out the top 3". I plan to run only a front brake, no back brake, the bike is so low the brake pedal would scrape when I turn. I plan to use clip-ons mounted below the top plate of the triple tree.






The look I'm going for. Low and sexy. It will prolly not handle good, be stiff, be dangerous but fuck it. It should look cool. I found a 19" front wheel in my shed I'm going to try to use. This one is the stock 18" wheel.


DAYS LATER

I got some work done this weekend. I mounted the seat support bars and did some sheet metal work.



I bent the edges of the sheet metal by beating it with a body hammer over a round pipe to match the contour.


Fully welded. Almost.
 

joeficsit

New Member
Re: New CB350 Project - Ball Breaker

i thought cb350's came with 19" fronts? that's good to know that some came with 18's so that i can use it on my cb200. keep up the good work.
 

dynamitedave

dcclassiccycles.com
Re: New CB350 Project - Ball Breaker

CL350s came with 19" front wheels
CB350s and CB360s all had 18" wheels.

My CB350 Bobber has a 21" front wheel that came off a '72/'73 SL350. Uses the same street hub as the CB350s with front drum brakes. Wish I could find some more of them.
 

dynamitedave

dcclassiccycles.com
Re: New CB350 Project - Ball Breaker

I cut a 2" section out of a gas tank, looks good, need to weld it up tho.


Also made a little tray to recess the battery in the swing arm
 

VonYinzer

Active Member
Re: New CB350 Project - Ball Breaker

Seems way too low to be rideable man. Maybe thats just because its sitting on the table though.
 

VonYinzer

Active Member
Re: New CB350 Project - Ball Breaker

Also... It the backbone only welded into the stamped steel at the bottom of the neck with the top just made from sheet metal?
 

VonYinzer

Active Member
Re: New CB350 Project - Ball Breaker

Ok, last one... Are you aware that as you have it built now, that frame is probobly going to fold in half? Not trying to be a dick, but you could really get hurt.
 

dynamitedave

dcclassiccycles.com
Re: New CB350 Project - Ball Breaker

This is why I usually don't post up my bikes until they are done. There is always someone who thinks they are a mechanical engineer. I didn't show every little detail but the backbone is welded in the neck along with added supports, it's welded to the existing pressed sheet metal frame and tied into the main structure with added support. The sheet metal I used is the same gauge or thicker than the existing sheet metal. It's much stronger than a stock frame which it needs to be since this is a hard tail.

The bike is low but not too low, I rolled it outside and checked before I welded it in place. It's too low to use the stock foot pegs since it has that bar that comes under the engine. I'm also not running a rear brake so the pedal won't get in the way.
 

VonYinzer

Active Member
Re: New CB350 Project - Ball Breaker

Wow man... You dont have to be a jackass.
The fact is that if its not perfect, it can fail. Some of the things in your pics look shady. If you did more work to sure everything up, than show that too.
I never said I was an "engineer", just asking questions to look out for/help out fellow builders.
Since you apparently have it all wrapped up just fine, good. When/if it fails, I hope youre wearing a helmet.

In the end its your ass... Do whatever the hell you want. If you dont want people commenting/asking questions, dont post pics.

Best of luck.
 

dynamitedave

dcclassiccycles.com
Re: New CB350 Project - Ball Breaker

Easy killer. I don't think I was a jackass, I'm just having fun. I'm not going to take a million pictures showing everything I do to the bike and post them up, that would take forever and be boring. I post up pictures of good progress with the idea that viewers can use their imagination and fill in the blanks.

Build a real hardtail? You mean buy a pre fabricated frame and bolt parts on it? That wouldn't be any fun. I like cutting, forming, shaping and welding metal.
 

VonYinzer

Active Member
Re: New CB350 Project - Ball Breaker

No. I mean a frame that doesnt use the swingarm as part of the "hardtail". Again, its your bike. Do whatever the hell you want. But if you post pics of unsafe mods, people will call you out. I also dont know of any bobber/chopper builds here that are all "bolt on" cookie cutter deals so Im not sure what that comment was about. And really man, I wasnt giving you a hard time. I was asking reasonable questions about the integrity of your frame. Seeing as you apparently have it all under control, forget I asked. Best of luck.
 

PHeller

New Member
Re: New CB350 Project - Ball Breaker

Despite the structural integrity of the rear frame, I'll just comment on the design.


It doesn't look cool. I don't like seeing the swingarm joints. The whole rear looks pretty messy. I'm not seeing any flow to the lines, not only that it doesn't have the cool "open area" left in the rear frame on a proper hardtail.


The front is pretty rad though. Nice call on the tank chop and hiding the front frame gussets.


I'd try to simplify the rear and make it flow with the front frame sections.
 

dynamitedave

dcclassiccycles.com
Re: New CB350 Project - Ball Breaker

I left the swing arm in tact for ease of building. Leaving the swing arm mounted ensures the back tire winds up where isn't supposed to, also ensures the sprockets line up and the tire is true horizontally and vertically. Someday I'll build a jig to hold everything in place for now I did it this way.

The "open area" you call cool looks ridiculous to me. I don't like when they stretch out the bikes and have a big voided space between the rear wheel and engine.

I think it will all come together when the bike is painted and all the parts are on it. Most people won't even notice the swing arm is bolted in.
 

Ringo

Active Member
DTT BOTM WINNER
Re: New CB350 Project - Ball Breaker

The swinger was the first thing I noticed too. Again, like everyone here, not trying to be a dick, but when you spend that much time welding up the frame...and leave the swing arm...? It looks like any other half-assed "hard tail" people post up. Give yourself some credit and don't cut that corner. I know I would regret it down the road when I admired my bike. Hope you don't!
 

Slice

New Member
Re: New CB350 Project - Ball Breaker

There is clearly a lot of questions surrounding the safety of this build... You question it yourself in your first post when you say "It will prolly not handle good, be stiff, be dangerous but fuck it. " Having said that, you already understand that fact, so no one needs to point it out to you.
From an aesthetic persepctive, i cant see what it will look like but I have a feeling its not going to be my 'bag of tricks'... however, to each their own!
Good luck man.

Slice
 

beard

pro blowhard
Re: New CB350 Project - Ball Breaker

just weld the swingarm solid

im guessing u dont want the front of ur seat angling down...
so add another pipe from the rear to the main frame beam to level out your seating.
then cross ur fingers


running without a 2nd brake... is sketchy.

may i suggest these
 

tWistedWheelz

BUILT NOT BOUGHT!
Re: New CB350 Project - Ball Breaker

I think this whole thing has been blown way out of proportion! I think the work done on the rear end is structurally sound given you add some gussets, which I am sure you plan on doing. I see no problems with your welds, they look great and I think you have ample support for the rear end. If it were me, I would leave the swinger as you have for my jig and then weld another tube from the bottom frame rails back to the swinger just in front of the axel and lose the rest of the swinger then. The structure will be supported then and no longer require the swinger for a jig, and that may very well be your plan. Where the work does raise concern to me is the top part of the frame where it meets the neck. I think with all the work you are doing and the skill you have, it would be no problem for you to get rid of all that stamped steel and put in a solid tube spine. Once that and the swinger are removed you could gusset up and clean up the old lower backbone area that is stamped steel. As far as being unsafe, well I am not sure if it is or is not with what you have done on the neck area, I simply can't tell from photos what all work you have done there, but I do know that a solid single tube would clean it all up nice and offer you better support than the old stamped steel. I really dig that low seat and it seems to me that with the one added support I mentioned, you would actually have more support that needed to be safe there. I hope all of this lashing you have received does not hinder you from this site or from showing us your work. This is a really nice bunch here and sometimes as a regard to safety, some people can come across wrong. Text does not carry attitude with it well sometimes, and it may come across derogatory when it was intended to be constructive. Good luck on your build. I will be excited to see what you come up with!

Cheers,
Brandon
 

VonYinzer

Active Member
Re: New CB350 Project - Ball Breaker

The problem is Brandon that there is no "neck tube" on a 350. Its all stamped steel. Just a few layers of it. When you cut that away, its nearly impossible to make it strong enough. And honestly, I wasnt trying to give you a hard time man. I just dont want to see ya put a ton of time/effort into a build and have it be dangerous or unrideable. Im down with your effort to do something different than whats out there. Just didnt want to see it be a futile effort.
 
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