SOHC.co.uk Forums > CB350/400

Before I took it apart.....

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Arfa:
So, I bought a complete UK bike in fairly good outward condition, with the intention of riding it and eventually doing it up. MOTS over 5 years or so show a consistent mileage story, with the bike doing less than 100 miles a year. I think I'm the 8th owner.
I thought I'd get a couple of "before" pictures out there- but don't count on any "after" ones for a few months at least. I should say that my default position is to keep the spanners off something (apart from services) unless I'm pretty convinced that there's something wrong.
In summary I've found it to be relatively unmolested. As purchased engine very quiet, but idle lumpy sometimes. Used a bit of oil, not spectacularly bad. Plugs Ok, number 1 very slightly fouled. Smoked a bit on start-up sometimes. Oh, and front brake poor. The two things that led me to dive into it were the rate at which the oil became dirty, and the smell of the oil, plus the engine, although keen to rev right out, didn't seem to be especially willing. This after I'd done about 250 miles on it.
Long story short is that piston 1 no top ring and a partial second ring- head well bashed by fragments, pistons 2 and 3 broken top rings, piston 4 OK. Barrels relatively undamaged. Cam chain adjuster half moon seized at pivot. Not much else wrong in the engine.
On the frame the lower cross piece (above the stand) had rotted out underneath and been poorly repaired. Otherwise mostly cosmetic problems.
I'll pop in more details as time allows.
By the way this forum is obviously useful but don't discount how encouraging it is as well, so thanks to all of you for that.
Arfa.

Nurse Julie:
Good looking bike there Arfa. Bloody strange how, by your description, your engine damage is the same as mine and Craig CB400's, pistons 1,2, and 3 all damaged but No.4 unaffected. I wonder just how many other CB400's have had the same damage that we are unaware of?.

K2-K6:
It's a bit of a pain that you've had to work on it so soon, as you say it's generally quite a decent example, or appears so from the photos.

Certainly for anyone working on them, the thread by Julie is a very comprehensive guide not only technically but as genuine encouragement to others to push aside reluctance and get stuck in to get them up to scratch.

Interesting that you've got a third ( think it's 3) example of very similarly internal problems on here. This sort of problem is very often put down to "carbs need tuning" by seller's when advertised.

Hope you get it sorted so you can enjoy riding it.

Laverda Dave:
Nice looking bike Arfa. Best advice is to check out Julies thread, read it and digest it and don't be afraid to get the spanners out. Any problems, we are here to help.

K2-K6:

--- Quote from: Nurse Julie on February 02, 2018, 10:03:45 PM ---Good looking bike there Arfa. Bloody strange how, by your description, your engine damage is the same as mine and Craig CB400's, pistons 1,2, and 3 all damaged but No.4 unaffected. I wonder just how many other CB400's have had the same damage that we are unaware of?.

--- End quote ---

Julie, it's interesting (as you've pointed out)  that more have turned up with that same 3 affected and the same one intact cylinders. Certainly starting to look more of a consistent pattern.  As an initial thought,  one clear difference that exists is the exhaust header pipes differ in length which would mean they have a different rpm point at which they are effective / less active on a cylinder by cylinder basis. The longer the pipe, the lower the rpm at which the scavenge affect on the cylinder is most effective. If the number four pipe being the shortest is coincidentally at its best when the other cylinders are in trouble,  then it could makes the difference. Generally it's best practice to make them all the same,  this series of Hondas all have the odd lengths though.

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