Restoration project - CB400F 1975.


New Member
Hi to all,

I have been loorking around this forum for quite some time now, but I haven't registered until I have started my own project.

I have purchased the CB400F in rather poor state, but all original parts were there an it was a good base for what I hoped will become a Cafe racer project. But somewhere down the stripdown process, where I have seen the real state of the original parts, I have chose to make an restoration of the bike. So here I am, starting this thread to show my progress and to gather some useful tips and advices during the process.

Here's the bike when i brought it home:

Frame and other bits were powder coated, so I started with reassembly.

Seat lock repainted, and reasambled.


Fuel tank paint stripped down




Fuel tank had a dent on left side, so it was sorted out. Next job is to clean and seal interior of the fuel tank. Anyone had any experience with POR15?


I have started to clean the carburetors, which were in horrible state from the outside, on the inside only one was in poor condition, and will need new float and jets.

Spring cleaned

That's it for now. Progress is slow but I hope that I'll have project finished by next riding seaon.

Welcome in mate you chose well for a first bike resto ya cant beat these little gems for a project. Get hold of a manual take pics as you go make notes and enjoy the process and most of all make her yours! always here for Q&A's ideas .
Thank you for kind words.

I do have a question though.... Engine painting. Is it better option to do it while it's in one piece, or to disassmble and to paint part by part?

I usually take all the covers and ancillary pieces off then spray as a block mate its easier and saves on masking up also if the motor doesn't need stripping down for mechanical reasons I wouldn't strip down just for paint it would up the cost of painting for all the new gaskets etc ,less chance of making a mess putting back together too, sure others will have different ideas but that works for me .
POR15 works great just be sure to prep it well use phosphoric acid to derust and etch then rinse with denatured alcohol before coating.

Sent from my iPhone using DO THE TON
If the tank is good inside why coat it? Keep it full of gas and use sea foam or similar to keep the ethanol issue minimal.
That's certainly a great looking starting point for any project!!! Cool little bike...subscribed.
Thank you for encouragement. 8)

I was thinking about the POR15 because it will postpone(and maybe eliminate) rusting of the tank. Inside job even now isn't too good, so I think that any additional protection would be better option in the long run.

I have had carburetor parts polished. The exhaust flanges were chromed.





That's about it so far. I need to have carburetor bodies soda blasted so I can start an assembly.

Nice work mate , my first build was a 400/4. Honda do a parts manual for this bike i found it a real help when seeing where bits went and when ordering stuff . Theres a tappet adjuster Honda do as well its a great help when you come to that point.
And theres David silver spares here in the UK if you cant find what you want there.
Keep up the good work.
Right - don't seal the tank unless it leaks. POR-15 works great if it does. Left bare, it should not continue to degrade as long as good fuel is in it and it gets ridden at least once in a while. In my experience, most of the time tanks go bad is because they were left to sit for a long time with untreated or alcohol mixed gas in them. Moisture accumulates in the tank, and being heavier than the fuel sits on the bottom where it rusts and creates pinholes. Very often a simply dry empty and rusty tank will clean up perfectly. Phosphoric acid seems to be the preferred miracle cure for most people. I often use hydrochloric myself because it is virtually instantly effective but it requires very thorough neutralizing (Also MUCH nastier in the first place) which is problematic.
Thanks for the advices, guys... I'll take a look inside the tank with the camera, and see... If it's in decent shape, I'll leave it as is. I can allways do it later if i see that tank starts degrading rapidly. ;)
Welcome to DTT! I have one of these babies, myself. I need to restart the resto process.
Happy to have you here. Looking forward to seeing your progress!
jpmobius said:
Right - don't seal the tank unless it leaks.

Exactly. There is no need to seal unless it leaks or you are killing inline fuel filters with contaminants. When it does start to leak POR15 is great.
Thank you for support and kind words.

Here is some progress. Two of the fins on the cylinders were broken, so i had them welded and recreated.



Also made mysef some simple engine stand.

Next step is the painting of the engine and remounting it to the frame. If I'm lucky enough to find some Duplicolor paint here in Europe.

Sorry for late reply.

Unfortunately, I haven't been very active on the forums and in the garage lately, due to my obligations.

Anyway, it's going forward but in small steps.

I have taken the front rotor off, and striped the paint down.

Afterwars, painted it with the Dupli Color matt black and baked it in the oven.

Also, central stand is lubed and mounted back on the bike. I don't know if I will keep it on once I finish with the assembly, but for now, I'll keep it, since it's a lot easier to work with the bike with the central stand.

Also, triple tree is assembled and new bearings are lubed and mounted.

Also, I have started to assemble the bike back together. I have lubed and put the swingarm on the bike.While I'm in a wait for some of the new parts, i will putty and prepare the tank for the paint. I think I'll paint the letters on the tank and side covers instead of the decals.

Here where's at the moment(with my 4-legged supervisor ;D )

That's it for now. I hope that this project will progress slightly faster from now on...

Regards, Kristijan
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