1975 CB400F "un-cafe"

[kartin]

As I mentioned on my new member intro thread, some time back I had started a project thread on the US site since that's where I am physically but I'm keen to get more exposure to the 400-specific knowledge here on the UK site. I've decided to just duplicate each post on both sites. Of course the first few posts here will just be to catch up with where I've got to so there will be a flurry of them to begin with that are not in "real time"! Also, I'm not going to post all the back in forth with people who replied - if you're interested, you can see those on the US Project Shop (same topic title).

[kartin]

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!

Here are some pics of the starting point - no laughing!

[kartin]

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 mentioned that it ran but just to elaborate a bit. I jury-rigged some wiring (there is no no real loom), set timing, checked valve clearances, fresh oil+filter, cranked until I saw oil from cam spray bars and then tried to fire it up and it ran fine, so that's a relief! Carbs now bagged and ready for the rebuild.

[kartin]

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.

[kartin]

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.

[kartin]

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.

[kartin]

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!

[kartin]

As I mentioned at the outset, first target is just to create a usable, more or less standard bike so engine has gone back in without a full rebuild. When I gave it a brief run after I first got the bike, it ran well with no smoke or major rattles. I also looked inside the tappet covers while it was running and could see all the camshaft oil sprays working. Also had the borescope down the plug holes and bores look good. So, good enough for now... I have a compression tester but not the correct adapter for these plug threads so I'll check it in the future. Also I'll likely pull the valve cover and check the tensioner and guide blades before I do any lengthy running.

I got the engine out of the frame with the sump/oil pan still on but of course, to get it back in while preserving the newly painted frame, off it came. There was a little bit of detritus on the screen plus some sludge near the oil drain plug but I'm not sure if those would be considered bad amounts? The engine internals looked great visually - certainly no chipped gear teeth or anything like that. While I had access to the tensioner arm (by reaching in with a screwdriver), I released the camchain tensioner bolt and wiggled the tensioner arm and could feel it moving so it's not seized. All engine mount bolts were cleaned and anti-seized and I made very sure the lower bolts were not reaching right through their nuts and risking any case damage. Gearchange shaft oil seal had been leaking so was renewed. Still some cleaning to do around that area under the sprocket cover!

[McCabe-Thiele (Ted)]

I like your spray booth & gantry set up.
.

[Bryanj]

As you are in US you may find it easier to get a 360G5 front end which is the same

[kartin]

As you are in US you may find it easier to get a 360G5 front end which is the same

Good know, thanks! Actually looking at some images of that model, the fuel tank looks suspiciously like the one that arrived on my bike!

[kartin]

Steering as received had a very noticeable notch in the straight ahead position so new bearings required. For the steering tapers, I plumped for the All Balls kit. Maybe not the ultimate quality bearings but as a kit, it seemed to be the one people had fewest issues with in terms of the height. The thinner washer gave a lower stack height very, very close to the originals (18.6mm for lower washer plus complete bearing). In the first picture below, original washer plus seal plus bearing is on the left. The freezer trick for the outer races and the stem worked well and fitting was very easy. At the top, I chose not to use the extra washer between the new seal and the adjuster nut, just to get some extra thread as well as bring the dust cover closer to the headstock. The very top nut had plenty of thread to work with.

The forks themselves were dismantled, seals replaced (very stubborn!) and everything flushed with brake cleaner. One of the seal retaining clips was too corroded to re-use which is why you see shop towel wrapped around it until I can add it to my next parts order (ok, I could have used the rubber cover itself but I wanted a visible reminder!). The stanchions have a few blemishes but the chrome is complete so no immediate attention required.

[kartin]

Just continuing to attach things to the frame. On the plus side, I'm very happy with the wiring loom. It came from classicjapanesemotorcycles.com and it looks almost brand new. The combined reg/rec came with the bike but it has zero markings so I'm not sure what brand. It was giving good voltage when I ran the bike briefly and I also metered the diodes so it seems good. It was originally wired in with a horrible rat's nest but I'll ditch all that and go straight into the loom regulator and rectifier locations. For now I'll use individual spade connectors but eventually I'd like to find the correct mating halves (source?). I have an alternator harness waiting in the UK for my next trip (from 400fourbits.co.uk).

On the downside, some more non-CB400F parts came to light. The coils don't look quite right (wires in different places) but they measure as 5ohm primary and 15k secondary and fit under the tank so that's fine. The handlebars only have a wiring hole on the left side and the clamp lines don't align with the clamps. I knew the switchgear was wrong. Neither side has anything related to the headlight and the horn wire goes to ground when pressed. I can also see that I'm missing various cable guides. So, more parts on the missing list!

[kartin]

Few more pics that wouldn't fit on prior post:

[kartin]

A bit of exhaust progress and it has some bearing on which way the project goes. From the beginning, I wasn't sure whether to aim for standard appearance or to try and mimic my old bike as it was when I finally sold it. The exhaust that came with the bike comprised standard downpipes but aftermarket muffler (without much muffling...). The downpipes are very rusty so either black paint or re-chrome would have been needed. But then what to do for a muffler? A repro in chrome might not look good with black downpipes?

Anyway, this dilemma was solved when I chanced on somebody selling one of the old Yoshimura pipes. These are the ones with the funky "crossover" arrangement and is exactly what I had on my old bike. The only photo I can find of the old bike is from the left side but you can just about make out the #4 pipe sticking further forwards than the others. The other pics are the seller's. Rust-wise it's not perfect, but it's probably going black anyway! Pipe is waiting for me in the UK so fingers crossed it will fit in our suitcases coming back!

So, for the rest of the bike, I won't go as radical on the colour scheme (it seemed like a good idea at the time and I obviously had an aversion to any chrome finishes!). But I still like the "high at the back" tail/fender look and the non-chrome front fender.