Author Topic: 1975 CB400F "un-cafe" (Read 3028 times)

Kartin · « **on:** June 16, 2022, 06:50:21 PM »

Had a CB400F back in the 70s/80s - see my Intro for back story - and wanted to re-create my youth. I was about to post a "WTB" on the US forum when one popped up really cheaply on craigslist. Of course it was rough and not running but it had correct paperwork (so many don't...) and good compression so I went for it. The bad news is that somewhere along its life it had received a poor cafe conversion attempt and was missing the original tank, mudguards, instruments, front wheel, front brakes (it has a drum brake!), muffler/silencer and lights. I want to gradually bring it back towards standard or maybe even a re-creation of my old bike. I'm certainly not looking for concourse - just a usable bike that at least has the appearance of a CB400F!

So far the progress has been to clean the carbs and go through all standard service items and then it sprang to life quite nicely with no smoke or abnormal rattles - result!

Will post some pics as soon as I have my 5 posts up.

grcamna2 · « **Reply #1 on:** June 19, 2022, 01:32:01 PM »

subscribed

Don R · « **Reply #2 on:** June 19, 2022, 02:26:11 PM »

I believe the front end is the same as cb360 similar year. (they are cheaper and easier to find) I'm sure the fork lowers and tubes are, I've swapped them.

grcamna2 · « **Reply #3 on:** June 19, 2022, 03:16:21 PM »

I have a freshly restored complete stock front caliper(I have pics if interested)for your bike with 0 miles on it.
I also have a front disc wheel in excellent condition.

Stev-o · « **Reply #4 on:** June 20, 2022, 10:13:05 AM »

subscribed...

Kartin · « **Reply #5 on:** June 26, 2022, 07:30:18 PM »

Quote from: grcamna2 on June 19, 2022, 03:16:21 PM

I have a freshly restored complete stock front caliper(I have pics if interested)for your bike with 0 miles on it.
I also have a front disc wheel in excellent condition.

Much appreciated! Definitely interested in the caliper itself (I have the little swinging arm thing). Will PM you to discuss more. I did manage to source a wheel and disc - my own fault for being a bit behind with my posting here otherwise I would probably have bought that from you as well. Actually I may still since the one I found has a couple of patches of rust in the tire well. Pictures coming soon...

Kartin · « **Reply #6 on:** June 26, 2022, 07:53:34 PM »

Ok, I think I'm eligible to post pictures now so here's the starting point - no laughing!

Kartin · « **Reply #7 on:** June 26, 2022, 08:06:26 PM »

PO said it was running up to about a year ago but didn't know any more other than "it wouldn't start". Carbs were as expected for a bike that had sat but responded nicely to some Berryman's. I then jury-rigged some wiring (no real loom), set timing, checked valve clearances, fresh oil+filter and it ran fine, so that's a relief! Carbs now bagged and ready for the rebuild.

Stev-o · « **Reply #8 on:** June 27, 2022, 07:01:45 AM »

Isnt that a 350 fuel tank?

MauiK3 · « **Reply #9 on:** June 27, 2022, 07:54:01 AM »

Sure looks like one.
Drum brake? interesting retro mod, I don't think they ever had a drum brake.
Cool project.

Mark1976 · « **Reply #10 on:** June 27, 2022, 07:54:51 AM »

Congrats on the purchase and all the best moving forward, but you've got yourself a project. If ya need a correct tank (75/76) I've got one, and if I were you I'd dump the pods as well, as I'm pretty sure I have a complete air/battery box but I'd really have to check. So, yeah go at it.

Kartin · « **Reply #11 on:** June 27, 2022, 12:45:45 PM »

There was a dismantled CB350T (not F) project on Craigslist a few weeks ago. Below is a zoom in on its tank - looks a lot like mine!

@Mark1976 - I was thinking it would have to be a DSS reproduction for a replacement tank so if you've got a decent original, I'm definitely interested - will PM. And yes, pods will be ditched (thanks for offer but I found a manifold and air/battery box already).

Stev-o · « **Reply #12 on:** June 27, 2022, 01:01:19 PM »

Quote from: MauiK3 on June 27, 2022, 07:54:01 AM

Drum brake? interesting retro mod, I don't think they ever had a drum brake.

I dont think so either. I have seen some bikes that were fitted with a drum brake but typically a double leading type system. My '67 CB450 Bomber has it, came stock, I like it on that bike.

Kartin · « **Reply #13 on:** June 27, 2022, 01:17:07 PM »

My thinking for the next steps are to:
- dismantle it down to bare frame (almost done)
- fix the places where the frame itself has been "molested" - see below
- paint frame, stands, yokes etc.
- new swingarm bearings (already ordered from Nurse Julie) and taper head bearings. The swingarm pivot came out really easily so no horrors there!
- then start building back up, creating a shopping list as a find out what's missing.

Regarding the frame, here are the areas that need addressing:
- fill holes with weld where that ally side panel was screwed on
- craft and weld on 3 new side panel "hooks" that were cut off (and what is that grinding gouge on frame rail - something else missing?)
- cut off the tab where the coils had been moved to accommodate that fuel tank
- cut off the stubs that hold the front tank rubbers and weld new ones back in correct position
- what's going on with that piece brazed to the sidestand mount? Is that a repair or has the stand mount been moved? Hard to tell without an original side-by-side.

MauiK3 · « **Reply #14 on:** June 27, 2022, 02:50:12 PM »

Painting the frame is always a decision point. Many use powder coat which is very good, I use POR15, it’s extremely tough and easy to DIY.
Loving the project.

Gurp · « **Reply #15 on:** July 02, 2022, 02:01:13 AM »

Following

MauiK3 · « **Reply #16 on:** July 02, 2022, 07:54:15 AM »

Keep us posted

Kartin · « **Reply #17 on:** July 07, 2022, 06:42:30 PM »

First time in garage for a few days and worked on the frame "repairs". Crafted 3 new side panel "hooks" and cleaned up the remains on the frame to get a straight edge to weld to. Will do the final metal cleanup right before I weld. Right after I posted last time, I realised what the other missing item was - the front helmet lock/holder. Not sure if I'll ever need two again but I certainly used to use them on my old bike so I'll add it, just for memory's sake! On the side panel hooks, I didn't make the little "ears" that hold the rubbers on - will try and put a little blob of weld on each corner then file it to shape.

The stubs that hold the front tank rubbers turned out to be a tube all the way through! Who knows why that was done but I'm not going to try and get it out...

Also got the head races off/out and carefully measured the lower stack, ready to decide which spacer I'll need on the tapers. Still not 100% decided between All Balls, Pyramid and DSS - have read good and bad about each, in terms of leaving enough thread at the top.

grcamna2 · « **Reply #18 on:** July 07, 2022, 08:21:16 PM »

Will you get the frame sandblasted after the mods are complete? it looks like it needs it,imo.

Kartin · « **Reply #19 on:** July 08, 2022, 07:04:38 PM »

Ok, some final grinding and smoothing to be done but I now have something resembling a normal frame! the welding is all on the back side of the hooks - it's not just those little bits you see on the seams. Also, that pinhole in one of the filled holes is really exaggerated in the photo - the paint will fill it easily.

grcamna2 · « **Reply #20 on:** July 08, 2022, 07:57:46 PM »

Good to see you bringing it back to stock and 're-tabbing' what was removed before.

Kartin · « **Reply #21 on:** July 11, 2022, 06:16:59 PM »

Was just glancing back through this thread and I think I missed the concern that the whole front end may have been swapped? Anyway, looking at the forks they seem to be regular CB400F since they have the disc brake caliper mounting points and they accept the CB400F axle that I acquired. The only thing that was changed was to weld on a boss to lock the drum brake backplate (which I will just leave alone for now).

Kartin · « **Reply #22 on:** August 02, 2022, 06:38:26 PM »

Starting to get paint on some parts. I'm all about DIY so I use wire brushes (on a drill for the heavy removal, on a Dremel for light removal and tight spaces) followed by a good de-grease until shop towel with mineral spirits stays clean. I use Rustoleum Stops Rust primer and satin black. Primer is Rusty Metal or Clean Metal depending on the state of the part being painted. I've used this combination on the chassis and floor of my homebuilt car which has been on the road since 2006 and it's stood up brilliantly. Have also used it on my RD400 and it looks correct (to me) and, again, has lasted well.

If you're wondering why a SOHC devotee has an RD400, there were two distinct camps in the UK when I was riding my 400-4 through the late 70s and early 80s. The Honda 4-stroke camp (400-4, 400T and 250/400N Superdream) and "the rest" which were all 2-strokes: Yamaha RD250/400 and 250/350LC, Suzuki GT250/380 and X7, Kawasaki KH250/400. So, when I decided to get another 70s bike about 10 years ago, I thought I'd see what the "competition" was like! I found someone who was selling all their RD stuff so I got one working bike, another in boxes and a ton of parts as a "job lot"! I cherry-picked all the best parts to make one good bike and sold the other. Hopefully soon I'll be able to make a side-by-side comparison test with the 400-4!

grcamna2 · « **Reply #23 on:** August 02, 2022, 06:58:35 PM »

Looks like it's coming along well Kartin;what type of sandpaper do you use ?

Kartin · « **Reply #24 on:** August 20, 2022, 05:12:51 PM »

Quote from: grcamna2 on August 02, 2022, 06:58:35 PM

Looks like it's coming along well Kartin;what type of sandpaper do you use ?

On these parts, occasionally some normal "wet and dry" to fade the edge of some original paint that I'm not removing. But I find that the fine wire brush on a Dremel leaves a perfectly acceptable surface by itself so I wouldn't sandpaper the whole thing by any means.

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Author Topic: 1975 CB400F "un-cafe" (Read 3028 times)