Requesting advice on frame cleanup

[reesea17]

Alright, expressing my complete ignorance in posting this one, but I really don't want to mess anything up.

I am preparing to start cleaning up my CB450's frame, i.e. cutting off excess tabs and chopping off the back in order to weld on a hoop later on in the build. I am far from experienced with an angle grinder and was wondering if anyone had any experienced advice to offer on the best form, method, and disks to use during the process. From removing one of the tabs I find that the grinder leaves a pretty rough surface behind. Do you then follow up with a flap disk or other type of smoothing disk to get the frame pipe back to smooth? What would be best? And is there any specific type of cutting disk thats better for removing the tabs and rear part of the frame then others?

 

[SONICJK]

Yup youre dead on,
Cut them off with a cutting wheel (really thin) and then follow up with a flap wheel to make it smooth.
I use a 60 grit flap wheel, and leave about 1/8 inch of the tab still on with the cutting wheel, so that you can finish it up with the flap wheel, that negates the risk of taking off too much material with the cutting wheel.

Just remember that these frames are absolute shit haha, dont cut too much off.

 

[Flugtechnik]

I used one like this (flap disc) when we were working on my frame at Kiley's. Worked really well. Used different grits to work down to a nice finish.

Also, make sure you know what every tab and such does and that you definitely aren't going to need it before hacking it off.

 

[reesea17]

So are you both advising that I forego the grinding disk and simply use a system of cut-off wheel to flap disks increasing in grit fineness in order to obtain a nice smooth finish?

I am assuming that these are all okay to remove. Air box tabs, seat latch, seat hinge tabs, helmet mount tab?, and I am wondering if I can remove what I am assuming was only the rear fender mount? I've seen people remove it before so I am again assuming that it is not a structural feature.

 

[yorkie350]

thats the best way mate lot quicker than grinding then clean up with flap wheels go steady these frames smooth down quick and ya need to keep the shape remember these are tubular ;D when i thought it was done blew over area with rattle can (black to match my frame ) to show any high / low spots or flap wheel marks always finish by hand 400 grade wet n dry 8)

 

[VonYinzer]

Are you not planning on running a rear fender? If that's the case, I'd highly recommend rethinking that.

You don't need a huge stock piece, but you want something there to protect the motor, carbs, electrical components, etc. from water and road grime.

The bike people see online that run with no fenders, velocity stacks, and so on are either show bikes or race only machines. Need to think in terms of real world practicalities when building a bike that'll actually get ridden.

 

[ronnie]

With the size of that rear fender mount, I would lean on the side of structural piece. If you remove it, I would look into welding something to act as it did to brace that two uprights. I'm no expert but you don't want flex when it never happened stock..

 

[Flugtechnik]

Once you cut the tab off, a grinding disk will help you quickly remove material you couldn't cut off without using up your flap discs, but once you get close to the frame, switch to the flap disc. Much more control. The coarse ones are actually pretty good at removing material.

What you are calling the rear fender mount, the big bottom thing in the last pic is structural. Yes the fender mounts there, but that is not its main function. If you think it is ugly, you can remove it and replace it with a piece of bent tubing (bent to clear the tire).

You also show you are going to cut the back of the frame off. Since you are doing a "brat" build, I'm guessing you are going to replace it with a rear frame hoop. You will need to. That piece is also structural.

All those other brackets can go.

Also, I agree with Yinzer. If you are actually going to ride this thing, find some way to mount fenders. They can be made more discrete, but you will miss them if you don't.

 

[Flugtechnik]

here is my fender:

Mine is actually trimmed a bit on the front to clear my new battery box, but normally I would leave it.


Rear frame hoop:

The web is there to mount the seat and taillight to (copied from XULF13's bike......which oddly enough is right there behind Chris in the pic).

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[yorkie350]

yeah theres some things structural ya gotta live with and ya gotta keep road crud off ya pods etc 8)

 

[reesea17]

Are you not planning on running a rear fender? If that's the case, I'd highly recommend rethinking that.

Definitely planning on running a rear fender, wasn't ever a question honestly. The reason I asked these questions is because I really like the look of the CB450's that Holiday customs has made. So I was seeing about the possibility of mounting a rear fender the way jared did on this CB450. But if y'all think its more structural then function I'll learn to live with it.

<a href="http://www.holidaycustoms.blogspot.com/2011/12/honda-cb-450-for-sale.html">Holiday Customs CB450</a>

You also show you are going to cut the back of the frame off. Since you are doing a "brat" build, I'm guessing you are going to replace it with a rear frame hoop. You will need to. That piece is also structural.

Yes, I am absolutely planning on putting a rear frame hoop in its place.


And thank you for all the advice along with your responds. I went to the store earlier and picked up a flap disk at 80 grit. I figure I'll do Flug's technique of cutting, grinding, and then smoothing out.

 

[Flugtechnik]

That thing is way too big to just be a fender mount. Like I said, you could always replace it with a piece of tubing and make it look nicer.


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[reesea17]

Alright, thank you all for the help. Just spent a little time with the cutter and flap wheel. Not perfect, needs a little bit of refining but I'm happy with the results. The flap disk was an awesome suggestion. Thanks again for all the help guys.

 

[yorkie350]

Thats the ticket mate looking good and keeping the tube shape already . I used the flap wheel to knock off some of the factory weld splatter while i was trimming frame down worth it man when it came back from powdercoat so smooth mmmm! 8) yours gonna be so clean too ime in on this one mate good luck

 

[manualofman]

Thanks for putting up this question, I was wondering the same things for my 450. These frames have so much splatter on them!

 

[reesea17]

They really do, I spent a good bit more time on the frame and it turns out much nicer and smoother. I'll post up example pictures later, don't really have a before and after on my favorite fix up but It definitely cleans up nicely.

 

[yorkie350]

glad it was worth it mate wait till ya get some paint on i was stoked with mine 8) ya see a lot of frame on a cafe so good prep work n paint job really show up nice bet ya got a buzz getting a better finish than the factory boys haha ;D