Author Topic: CB400F Super sport 1978  (Read 449 times)

Offline Jorgead18

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CB400F Super sport 1978
« on: September 23, 2018, 06:00:38 PM »

   My name is Jorge, I am looking to get a bike from my friend that has a Honda CB 400F super sport, this has been off the road for about 20 years and although it doesn’t have any rusted pieces or anything that looks that could be a major issue with it. I would like to know what sort of things I would deffinetely need to change or update?

    I live in south london so would appreciate a lot if anyone knows any garage or specialist that could help out with it.

Kind regards,


Offline Nurse Julie

  • 1973 CB750 UK K2.1977 CB550/4 Mongrel Brat. 1978 CB400/4.
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Re: CB400F Super sport 1978
« Reply #1 on: September 23, 2018, 06:55:11 PM »
Welcome to the forum Jorge. After 20 years of sitting around the bike could require quite a bit of work to get it rideable and more importantly safe. The carbs will definitely need a strip, thorough ultrasonic clean and new rubber 'O'rings and gaskets fitting and setting up correctly. The fuel tank may need a very good clean out, especially if rusty. The tyres will most probably be hard, dry and cracked. The engine may be seized but if not it will require a good service, new spark plugs, oil filter etc etc etc. New air filter. Tappets re set. The engine oil seals may have gone hard and brittle which would cause leaks, if so, to replace some of these requires a total engine strip down. The fork oils seals may need changing. Front and rear brakes overhauled with new pads / shoes. The clutch may be seized. This lot is just for starters......shall i continue. On the other hand you may find she starts up 1st push of the button and no need for any work at all but, i doubt it. Best to do all the work yourself if you can, specialist mechanics in these old Hondas are very rare to find these days. Good luck
Im a Nurse, trust me, this won't hurt.....much !!!

LINK TO MY CB400/4 ENGINE STRIP / ASSESSMENT AND REBUILD...NOW COMPLETE,14049.msg112691/topicseen.html#new

Offline Northy

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Re: CB400F Super sport 1978
« Reply #2 on: September 23, 2018, 08:18:13 PM »
Jorge , agree with Julie. 

Sounds like the bike is not too bad , picture would help.  Need to decide if the bike needs stripping down or is useable as is. Suppose The getting the engine going is key.
Remove plugs , drop some oil on the bores and turn the engine over by hand first , if moves you move on to stripping the carbs and clean, drop the sump (20  year of muck will be waiting for you to clean out ) and change oil filter and oil. Renew all plugs . Turn it over (borrow battery) check you've a got spark. Then add fuel via a dummy fuel tank . If starts its will smoke (oil in bores ) but if it carries on you've got issues . Turn it off , allow to cool , if on start up it still smokes then it a engine strip (valve seals 90% of the time) . If doesn't smoke then I  start on tappets, timing etc  moving on to the running gear. Your front brake will be seized !!!  they all do. Just recommission two with smokey engine on start up ...currently working on a thidr engine.
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Offline SumpMagnet

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Re: CB400F Super sport 1978
« Reply #3 on: September 23, 2018, 11:15:06 PM »
My 750 had a few issues that were not immediately obvious....

The camchain guides and wheels were rock hard and cracking....and there were several o-rings and oil seals that were well passed being useful. On top of that...when I chjecked the valves for sealing...they didn't on all cylinders.

I could have probably fired it up and got it running... but I don't think it would ever have run well. By tearing it down, I found the problems....and can fix the problems..but I also have found out a lot about my motor and how it all goes together. When it's done....I will know it's a good engine and not worry about the state of all those bits you can't see.
CB750F2 - in pieces
CB900F Hornet - the daily transport


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