Where to start? cb 350 to bobber project

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wannabobber

New Member
Got a 74 cb350 four (pictured here), wanting to bob it out. Found this picture of a cb350 bobber online...exactly what I want mine to look like. Where do I begin? Its me and a buddy, he is an experienced welder and ready to get this project started. Do we need to build a jig and all that first? Is it easy to just cut in to bike frames and weld on the new stuff and make it all happen? Any suggestions?, he usually works on mini-trucks, new at bikes. We have the 350 stripped down to frame now. Buddy is experienced with engine rebuilds and frame work on 4 wheel vehicles and all that good stuff....lots of experience, just trying to make sure we start off on the right foot for this project, any helpful comments would be great!

Thanks everyone!
 

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You WILL need a frame jig and you need to do a lot of research on building a rigid frame. The CB350f has a stamped and welded steel frame, so it is not as easy as just cut off and weld on! You would be better off just building a one off frame from scratch, which will require a good bit of knowledge to properly construct. Making a frame true and square is not any easy task, not to mention knowing how to properly structure it for strength in the correct locations. A botch job on a rigid frame could cost a life!
 
I found some plan designs online for both jig and hardtail, doesn't look like this one in the bobber picture though. How hard would it be to replicate this exact bobber in the picture?
 
Yup. Building a rigid frame can be a pretty daunting task. The Honda frames of the 70s dont easily lend themselves to it, but it is possible.
First off, you need a jig.
Then you need to determine the exact design you want, and make accurate measurements.
You need to use the correct materials (i.e. NOT PLUMBING PIPE) and your welds have to be extremely solid.
Rake, trail and any stretch has to be set (using the jig) and you can go from there.
All in all, if youre building one single frame, the costs of material and whatnot for a jig (can be built for around $250 or so) and the frame (probobly around another $200 for the correct material) could be more easily spent on a one off frame from a known builder. (Ive seen custom frames for as low as $700).
That said, wheres the fun in that? If you have the ability, tools, and time I say go for it.
Just make sure youre willing to take on the costs and work first.
In the end its your ass on the line.
 
Pretty hard considering the one pictured is of a twin and you have a 4 cylinder! You could however use the basic look, which is generally the same for almost all rigids. Your lower rails would need to be wider, and you would most likely need a double down tube, but still nothing that will change the overall look too much. I am not sure what you mean by both "jig" and "hardtail" as far as the "plans". You will need a full jig with a neck mount holding your neck at true and in the desired rake. To be honest with you, I am not sure I could type out all the steps you would need to do for a form jig and have you understand it! But generally speaking, your jig would need to hold your neck tube and your rear axle in space where you want it, and true for the entire build. You need supports that you will tack in temporarily until the entire frame is in place and final welded, including neck, down tubes, bottom rails, back bone (all the way back into bottom rails) engine brackets, tail section, axel mounts and all gussets. These supports will need to stay in place holding it all true and square until all the welds are complete, so that the heat from the welds do not contort the frame. There is a TON of info on the web for doing this. Just make sure you do it right! A home built frame of any kind can be very dangerous, especially a rigid.
 
Is there anyone that does this sort of work that has prior experience and cutting and welding and already has a jig and all? That might do it for relatively cheap? Someone that I could send or take the frame to along with the picture and have them create that frame and then I could do the rest? Wanna make sure that I'm safe, safety is of upmost importance to me. As far as the rest, I feel like it would be fun to cut and create some myself. I realize that the picture is of a 2 cyl and mine is 4 but I would think that it should still be very possible to create a bike that looks overall the same as this one pictured?
 
Yes, it is very possible to get that look. There are several people out the who build rigid frames ready to buy. all you do is fab up some engine brackets and then bolt the engine in there. That may be a good route for you to take. Also there are hundred of shop all over that will make you a frame, I am sure you could find one around you somewhere. With all that said though, I really hate to see you cut up that pretty little CB350f, I have a soft spot for those gems! But to each his own.....Good luck!
 
The bike in the pic is a pretty standard hardtail. Anyone who does frame building professionally could easily make that. As far as cheap... Well thats another story. A complete frame will run you anywhere from $600 and up. And $600 is really low. Another option you have is to buy a premade hardtail frame, and rewrok it to fit your motor. New motor mounts, and so forth. Something like this could work.

http://cgi.ebay.com/ebaymotors/TRIUMPH-RIGID-HARDTAIL-FRAME-60S-CHOPPER-BOBBER-650-_W0QQcmdZViewItemQQhashZitem19c2b171a7QQitemZ110640591271QQptZMotorcyclesQ5fPartsQ5fAccessories

If you decided to go that route though, you need to take a TON of measurements to ensure that your motor will even fit.

A lot of guys wont touch the Honda stamped frames when it comes to hardtails. Too much work and would cost the customer a fortune.
 
Please dont take any of this as a "you cant do it" speech... It can and has been done. We just want you to know how much time and effort you need to put into it.
 
I have thought seriously about cafe instead of bobber. I just really like the bobber look too well. I hate to chop it in a way too, but I want the bobber more than the vintage. Im not taking it like I can't do it speech, thank you though, I figured it was harder than orginally thought, so I figured this would be a great place to post and find out. I certainly don't want to have a bad accident all because I was foolish in building. Ill check around here local and see what I can find out.
 
You could always go "brat" style or whatever its called now. Simple frame mods and whatnot, but keep the rear suspension. You just get the bike really low, and stripped down. Kind of a bobber/cafe mixup.
 
Yeah, honestly your 350F is better suited to Cafe... build a bobber out of a twin, it will be much easier and cheaper... Plus, and this is just me, but I think 4cy bikes look kinda weird as chops...
 
Clean up the CB350 four banger and sell it - it's a very very collectible bike :) Buy something a little more suited to 'bobbing' like an XS650. Tons of simple weld-on frame kits available for the XS and the parallel twin looks the shit :)

Will also sound way more 'bobber' like than the tiny sewing machine powering the CB350. Don't get me wrong - I LOVE that bike, but it's no bobber base.

Would make an awesome cafe, or like I say, clean it up and flip it for $2000.
 
dakine_surf said:
Plus, and this is just me, but I think 4cy bikes look kinda weird as chops...
Click to expand...

I tend to agree.

The frame would however be much easier than a cb350 twin! ha!
 
One reason that a CB350F is not a good basis is that it has a small wide engine and bobbers typically are narrow. That upsets the look for a start. And basically everything else on that bike would end up being dumped because it wouldn't look right on a bobber.

I'd put the thing back together and sell it for whatever you can get for it and look for a twin preferably slightly larger say a CB450 or an XS650.

You can get one that isn't pretty. You will be throwing a lot of stuff away or replacing it.
 
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