SOHC.co.uk Forums > CB350/400
Where is the valve guide?
Bryanj:
Be aware that you can not just fit a valve guide and reassemble, the inside of the valve guide needs honing/reaming and the valve seat recutting, also the 350/400 fours do not have stem seals on the exhaust guides
K2-K6:
As already mentioned, unusual to get a sudden change in oil burning via guide and the oil going down through that way. Generally accumulative with wear over considerable mileage.
Possible ring break and compromise a cylinder. Run it after warming up and with a glass of oil with the breather pipe submerged to see if its sucking a vacuum in there and very thirsty :)
Could be a damaged piston, check that with a endoscope through the plug holes. Check plugs for an oily one too.
These 400 are stoic little buggers, running well with seriously compromised cylinder and piston very competently until finally found out how bad they've got :)
Has the motor been apart recently ?
Athame57:
What I'm hoping ( and praying!) for is that it's a repeat of something that happened years ago, a tappet had come astray, also causing strange noise, reduced power and smoke. I guess I could have nursed my way home and checked myself, but the workshop was closer and in this heat and my less than brilliant health just now I really aren't up to the job of spannering myself :( Oh well, I'll wait to see the verdict.
TrickyMicky:
--- Quote from: Athame57 on August 12, 2025, 06:08:42 PM ---What I'm hoping ( and praying!) for is that it's a repeat of something that happened years ago, a tappet had come astray, also causing strange noise, reduced power and smoke. I guess I could have nursed my way home and checked myself, but the workshop was closer and in this heat and my less than brilliant health just now I really aren't up to the job of spannering myself :( Oh well, I'll wait to see the verdict.
--- End quote ---
Dont' worry mare, you are not the only one. In my case, Anno Domini means that what I used to call my 'onda 'ospital is now only a minor injuries unit. I even have to have help getting the 400 onto the hydraulic ramp now.
Athame57:
--- Quote from: TrickyMicky on August 12, 2025, 11:08:08 PM ---
Dont' worry mare,
--- End quote ---
LOL! Am I female horse?
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