Topic: 1975 CB400F "un-cafe"

[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.

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!

[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.

[Stev-o]

Nice job on the front end.  Have seen countless questions on the tapered bearing upgrade, we even have a thread dedicated to it. You must have done your homework!

[Kartin]

I'm trying very hard not to invoke any "use the search!" comments, just to post my own experience which people can take or leave as they wish!

[grcamna2]

I'm trying very hard not to invoke any "use the search!" comments, just to post my own experience which people can take or leave as they wish!

Lol 
I understand.
Thanks 

[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.

[Kartin]

Back from UK trip with a suitcase full of goodies! The above mentioned exhaust looks pretty good so I might re-visit whether to paint black or not. I think I now have most of the clips/brackets/grommets that were missing. Also got some correct handlebar switches as well as an ignition switch. The handlebar switches check out fine on the meter but the ignition switch didn't show any continuity and wouldn't even turn to the park position. It has clearly been opened before but not cured. I found two issues inside:
- one of the springs that press the little "bridging" pieces onto the contacts was not in place. Maybe this was meaning it didn't sit properly and was preventing the switch from turning properly? Just a guess...
- the strips that form the connector spades are attached to the actual switch contacts by a sort of rivet affair. I found continuity to the rivet head but not on into the strip. I cleaned the rim of the rivet and adjacent strip with a dremel wire brush and bridged the two with solder (being quick so as not to melt the plastic holder). I only did the 3 that are easily accessible - the other 2 seem fine.

The combination of those 2 things resulted in correct operation and continuity in both key positions. In my haste to try it I forgot to take pictures of the solder fix but they are on the back side of the piece in the top-right of the picture with the fabric background (not my picture - just one I found). The other switch picture shows what I believe is the correct orientation of that piece into the housing to get the correct connections for each switch position (TBV when finally fitted to the bike). Continuity testing is made a bit confusing by the fact that there are 2 brown wire locations which are not connected when the switch is stand-alone but are connected in the loom, so you need to try both.

A huge "thank you" to people who have posted colour-coded wiring diagrams, including what wires should be connected in each switch position - they are invaluable for this sort of testing.

[wolf550]

looking good with everything!
I like that exhaust alot.
I wanted to keep the 4 in 1 on my wifes 350f but she likes the 4 in 2 on both sides.

[grcamna2]

looking good with everything!
I like that exhaust alot.
I wanted to keep the 4 in 1 on my wifes 350f but she likes the 4 in 2 on both sides.

That chrome exhaust looks very nice 

[Little_Phil]

Back from UK trip with a suitcase full of goodies! The above mentioned exhaust looks pretty good so I might re-visit whether to paint black or not.

That's a first, bits normally go the other way, but 400 was a big hit in the UK. Exhaust looks ace.

[Kartin]

Continuing to clean up the various bits. The hardest work so far has been the front brake components. I thought I would give the OEM originals I picked up a try before resorting to reproduction items but they have put up a good fight! Even the pads were well seized into the caliper halves, never mind the piston itself... So, freeze, heat, penetrating fluid, tap-tap-tap with a hammer and keep repeating the cycle, trying to break the corroded joints... Eventually the master cylinder piston yielded with some heavy blows via a drift in the banjo end. The bore looks surprisingly good so we'll see what happens there. On the caliper end of things I had to get really brutal to get the old pads out, basically drilling and chiseling until they came free. As for the piston, I thought I was being clever by drilling and tapping a hole in the face then using a bolt + washers to pull it out but all that did was pull the face out of the piston! I tried hammering the sides of the piston in to try and collapse it, to no avail. Eventually I did the drill+tap thing again, this time with the bolt bearing on the inside face of the caliper and out it came! You can see the big pile of grease on it from the attempted grease gun method (which failed). The sealing face is on the piston (which will be new, obviously) and the groove in the caliper (which looks good) so again, worth a try. I'm lucky in that I live in a neighbourhood with 25mph limit and only one entrance/exit to "regular" streets so I can test extensively in a benign environment. If the brake doesn't behave flawlessly, I will ditch it in favour of new parts before I venture out onto "real" roads.

[Kartin]

Continuing to clean/paint/refurbish/fit parts. Nothing much out of the ordinary worth reporting except for 2 points that might help others:
1) The new bronze swingarm bushes I had bought seemed VERY tight in the swingarm, even when frozen. I double-checked that the insides of the swingarm itself were clean and not marred from the removal of the old bushes - all good. I didn't want to risk getting stuck half-way so I chose to shrink them ever so slightly with some wet-n-dry while spinning them in the lathe - see pic. Then with freezing and grease they went in beautifully using the threaded rod method.
2) I had read that I should fit the rear brake pivot assembly before fitting the swingarm but I would add to that to fit the pull-rod to it as well, especially if you want to insert the clevis pin from inside to outside so you have access to the hole end. I tried to do it with the assembly in place and it was a fiddle.

[Kartin]

Back from another trip to the UK with a couple more parts:
- a CB250N Superdream (aftermarket) headlight: A mod some people use to enable using a 60/55W H4 bulb. I don't even have a CB400F bucket so I'm using the whole thing for now. This meant relieving the bucket a bit to clear the ignition switch and indicator bar.
- LPM sidepanels (I know they ship to the US but since I was going to the  UK and they're not hard to transport...). The material looks nice and meaty so hopefully they'll prove to be robust.

Also, on my Yoshi exhaust, I made a decision which I may regret... Despite looking in quite good shape in the overview pics, the insides of the first bends as the pipes leave the engine are quite rusty. As a bit of an experiment, I used some high temp primer and silver paint just on that first section. The idea was to stop them rusting further and for the colour not to be too obvious. The pictures really highlight the transition so we'll see how it looks once everything's together. In hindsight I should have just done the inside of the bend (fairly hidden). If worst comes to worst, I'll go full matt black which is how my original bike was anyway.

[Kartin]

Tail fabrication is under way. On my old bike I used a taillight bracket from another Honda but this time I decided just to fabricate that as well. The tail/mudguard might be on the long side but I can shorten it in the future if needed. Will decide once whole thing is together and I can judge the asthetics.

For the front mudguard, to stay true to my original bike, I wanted to go non-chrome. I have one that came with my RD400 (the white one in the pics). The bracket is all wrong, of course, so I was about to carve into it when a genuine 400-4 guard came up on Ebay. The chrome is a little speckled close up but it stands the 2 metre appearance test so for simplicity of fitting,  I'll go with it for now. I may go non-chrome in the future - from memory the one on my old bike was from a CJ250T since the front forks and braking setup is identical to a 400-4 so I'll keep an eye out for one of those.

Next, painting (tank, side panels, tail)...

[Kartin]

Getting closer to looking complete! Since last post, only 2 things out of the ordinary for me as I continued to rebuild:
- even with new bronze bushes, the swingarm had some play i.e. the tube was also worn. I experimented on some scrap tube to see if I could add a layer of weld then turn down to size on my old lathe but my skills are not up to it. As a temp solution, I wrapped some 0.05mm shim stock around the tube ends. This cured the play nicely but obviously this is not a long term solution so I'll search for a new tube.
- the front forks felt very stiff/sticky. I checked for straightness and alignment but it ended up being extremely tight fork boots and a light smear of lubricant helped enormously.

Rattle can paint job came out ok (Rustoleum sunrise red with Spraymax 2k clear - and yes I was careful with correct PPE), although my filler skills are as bad as ever. No matter how careful I am with my sanding blocks, I always seem to end up with the filler level a fraction low such that you see the outline of the filled area through the paint. Anyway, it stands the 3 metre appearance test ok. I did end up shortening the rear mudguard a bit to get the aesthetics to my liking.

Everything else was more or less standard re-furb/re-fit. I pulled the valve cover and thoroughly checked the cams, journals and also the rubber faces of the cam chain tensioner blade and guide. All seems good so as mentioned before, I'll run the engine as is for a bit then see if anything warrants a re-build. It starts and runs and I've been riding it around my neighbourhood. If you recall how bad the front brake cylinder and caliper were, miraculously it works great!

Immediate to-do list is:
- throttle response is a bit fluffy just off idle. Also, the float valves occasionally stick. So, it's off with the carbs for another go through...
- the chain is occasionally flapping against the chain guard so that needs a tweak (the guard is not actually a 400-4 item so it's already a bit of a kluge).
- find some correct mirrors.
- front brake works great once the lever contacts the MC piston but there's quite a bit of wasted lever motion before that happens. I seem to recall using a 1p coin as a shim in my original bike!
- indicator flash rate is far too fast (it's got some generic car item in it) so need to find a proper flasher.
- after a few miles I'll go over the valve clearance, timing, carb balance etc. again.

[grcamna2]

I'm surprised you never took me up on the offer of the freshly restored OEM original caliper I had offered you 1.5 yrs. ago;I imagine you needed to struggle it through. 

The bike is looking good. 

[Mark1976]

   Does that pipe have a baffle in it?

[MauiK3]

Nice bike!

[Kartin]

   Does that pipe have a baffle in it?

Yes, it's the perforated tube type and is surprisingly quiet!