Author Topic: 76 CB750K chopper. (Mod, please delete the other proj thread referenced inside!) (Read 5356 times)

TCSOHCB750CAFE · « **on:** September 20, 2010, 07:26:29 PM »

Aight. So I had a cafe project going with this, but ended up picking up a GSXR750L (1990) to streetfighter, so I've got a good performance bike now.

So.... instead of junking this CB, it's getting a chop setup.

(Moderator, please delete this thread as it's no longer a valid project: http://forums.sohc4.net/index.php?topic=71654.0)

I got some work done recently on the tank. So far, this is the main part of this project.

It's an old Wassel Banana tank. Condition was pretty poor when I got it.

It's getting some more body fill and sanding, then a coat of pearl white, then scales under candy red in the center top and lower side portions with a nice fade.

The holes get some brass window inserts threaded in. They come from hydraulic systems.

Next update will be more on the tank, bracing the frame for cuts, hardtail and extending the backbone, doing a single seat tube, and building a real simple girder fork.

Please stand by.

Ricky_Racer · « **Reply #1 on:** September 20, 2010, 08:51:30 PM »

Cool. Very "Steam."

RR

mystic_1 · « **Reply #2 on:** September 20, 2010, 10:32:40 PM »

Woah, me likey!

Moar please!

mystic_1

hapakev · « **Reply #3 on:** September 21, 2010, 07:10:41 AM »

very intereshting!

TCSOHCB750CAFE · « **Reply #4 on:** September 21, 2010, 06:53:29 PM »

There's more to come!

I started the jig for the hardtail that I want to build today.

I gotta get a few pieces of hardware that are proving elusive for how I want to do it, but once I do I'll post up.

-J

TCSOHCB750CAFE · « **Reply #5 on:** September 22, 2010, 03:53:22 PM »

Gettin JIGgy with it.

TCSOHCB750CAFE · « **Reply #6 on:** October 06, 2010, 10:18:57 AM »

Started cutting the frame and sorting geometries....

hapakev · « **Reply #7 on:** October 06, 2010, 04:04:10 PM »

I like it! That is a mean stance.

TCSOHCB750CAFE · « **Reply #8 on:** October 15, 2010, 09:24:17 PM »

Framework started.

Tubes extended and rear half of frame minimized. Everything is long in these pics. Nothing has been trimmed to spec yet. Will update again soon.

mystic_1 · « **Reply #9 on:** October 15, 2010, 09:48:57 PM »

Nice

Waiting with bated breath.

mystic_1

bathcollector · « **Reply #10 on:** October 16, 2010, 12:20:07 AM »

Quote from: TCSOHCB750CAFE on October 15, 2010, 09:24:17 PM

Framework started.

Tubes extended and rear half of frame minimized. Everything is long in these pics. Nothing has been trimmed to spec yet. Will update again soon.

Where you have joined the top backbone tube, have you put tube inside to brace the join at all ?? Tube should not be joined 90 deg, cut it at 45 deg and you have more weld area and less chance of a fracture, i know from experience this to be true.

TCSOHCB750CAFE · « **Reply #11 on:** October 16, 2010, 05:56:53 AM »

No, it's slugged with solid bar stock at the joint. Nothing is welded yet, it's tacked for measurement sake. Have to start on the hard tail, so I need to know where my points lay.

Your joint at a 90* on this tubing would be close to 4.5” around.

Cutting the tube at 45* would increase joint a small amount, but not enough to make a big difference in terms of cracking.

I'm quite confident, in my own experience, that when welded properly, a 90* tube joint with a slug is MORE than capable of handling the loads required in this capacity and more.

Another thing, I would assume you are MIG welding your joints? I say this because MIG welds are MUCH more prone to cracking, fracture, fissures, etc. than TIG. If possible, TIG your joints, give them a little preheat, and if you can find heat bags, use them once your weld is in to slow down the cooling process. It will help.

bathcollector · « **Reply #12 on:** October 17, 2010, 03:25:54 AM »

I gas welded mine, had a tube in it and it still broke right across the joint ? All my other welds bar the rear axle plates that were stick welded were gas welds, no other welds let go in 41000 kms of riding. The only thing holding my frame together was the saddle mount i had built into the fatbob gas tanks, rode it home 400 miles broken.

TCSOHCB750CAFE · « **Reply #13 on:** October 17, 2010, 11:06:33 AM »

Quote from: bathcollector on October 17, 2010, 03:25:54 AM

I gas welded mine, had a tube in it and it still broke right across the joint ? All my other welds bar the rear axle plates that were stick welded were gas welds, no other welds let go in 41000 kms of riding. The only thing holding my frame together was the saddle mount i had built into the fatbob gas tanks, rode it home 400 miles broken.

You use the term "gas weld". I assume you mean MIG welding. MIG is REAL PRONE to cracking when you back it up like that at a joint. The problem is that the backup you use pulls a lot of heat away from the joint while you weld, causing less penetration at the weld. The issue really is that the weld will still *look* PERFECT though. It's the reason MIG welding isn't often used for real structural stuff professionally, giving way to stick or flux cored dual shield welding. Better penetration. Preheating can help, but can also cause a lot of warpage.

TIG is really the best way to go on something like this if you have access to one. You can use a little preheat, and really watch the parent metal go fluid and puddle up nice before tossing filler in. :thumbup:

bathcollector · « **Reply #14 on:** October 18, 2010, 01:48:41 AM »

Quote from: TCSOHCB750CAFE on October 17, 2010, 11:06:33 AM

Quote from: bathcollector on October 17, 2010, 03:25:54 AM
I gas welded mine, had a tube in it and it still broke right across the joint ? All my other welds bar the rear axle plates that were stick welded were gas welds, no other welds let go in 41000 kms of riding. The only thing holding my frame together was the saddle mount i had built into the fatbob gas tanks, rode it home 400 miles broken.

You use the term "gas weld". I assume you mean MIG welding. MIG is REAL PRONE to cracking when you back it up like that at a joint. The problem is that the backup you use pulls a lot of heat away from the joint while you weld, causing less penetration at the weld. The issue really is that the weld will still *look* PERFECT though. It's the reason MIG welding isn't often used for real structural stuff professionally, giving way to stick or flux cored dual shield welding. Better penetration. Preheating can help, but can also cause a lot of warpage.

TIG is really the best way to go on something like this if you have access to one. You can use a little preheat, and really watch the parent metal go fluid and puddle up nice before tossing filler in. :thumbup:

No, gas as in oxy/acetylene welding. I agree on MIG, can fool you into thinking it's a good weld when it's only sitting on the surface.

TCSOHCB750CAFE · « **Reply #15 on:** October 20, 2010, 04:36:07 PM »

And something from lunch time. Had some free time...

They don't get used, but I wanted to have them for mockup purposes.

TCSOHCB750CAFE · « **Reply #16 on:** October 21, 2010, 04:23:56 PM »

45 degrees rake? Check.

TCSOHCB750CAFE · « **Reply #17 on:** October 27, 2010, 04:27:14 AM »

Ouch · « **Reply #18 on:** October 27, 2010, 01:38:07 PM »

Your idea is beast!!! this is an intersting follower....

TCSOHCB750CAFE · « **Reply #19 on:** October 29, 2010, 02:36:44 AM »

captaincrash80 · « **Reply #20 on:** November 02, 2010, 12:12:14 PM »

Man, I am really diggin that tank. GO GO GO!

COMB2 · « **Reply #21 on:** November 02, 2010, 06:51:24 PM »

Yea the tank is bad ass

TCSOHCB750CAFE · « **Reply #22 on:** November 22, 2010, 12:39:27 PM »

Small update. Waiting for other parts, then this goes out for polishing.

And this came...

Ricky_Racer · « **Reply #23 on:** November 22, 2010, 01:48:15 PM »

TCSOHCB750CAFE, it looks like you did a really clean 45 degree rake without a stretch. Have you got any detail photos of the rake job you can post? Thanks! RR

TCSOHCB750CAFE · « **Reply #24 on:** November 22, 2010, 02:39:57 PM »

I'm moving this Friday across the state, so the bike is all packed until then.

Once I get settled in and stuff tho, I'll do a writeup. Maybe I'll get someone who wants a rake done to send me their frame or something and document the process..

DaytonGuy · « **Reply #25 on:** November 22, 2010, 02:48:43 PM »

Quote

Maybe I'll get someone who wants a rake done to send me their frame or something and document the process..

Where are you located? I may be interested.....your bike looks sweet. I have a 550 frame.

Ricky_Racer · « **Reply #26 on:** November 22, 2010, 03:17:07 PM »

Really? Gee, I just might know somebody!

RR

TCSOHCB750CAFE · « **Reply #27 on:** November 22, 2010, 03:26:38 PM »

I'm in Minnesota. Once I move I'll have 220 again so I'll setup my TIG to do this stuff. I did mine with mig, which is fine, but I'd rather TIG a neck.

I make the plates and contour so the factory recesses are still there. Looks nicer than flat plates imho.

Lemme know.

I also have a frame jig, so I could do stretch and stuff where the neck needs to be completely removed.

Ricky_Racer · « **Reply #28 on:** November 22, 2010, 03:31:46 PM »

Cool. I'm in San Diego, but my bro is in Illinois. We both have an overabundance of CB750 frames. Let's stay in touch by PM.

Enjoy your move. I've done it waaay too many times; one of life's real pleasures!

RR

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Author Topic: 76 CB750K chopper. (Mod, please delete the other proj thread referenced inside!) (Read 5356 times)

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