SOHC.co.uk Forums > CB500/550

camchain tensioner

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bigmockuk:
video link https://youtube.com/shorts/bnGOP-TrCN4

Nurse Julie:
A few strange noises going on there. It sounds 'tappety', almost like a chipped tappet or misaligned or something that's not allowing it hit the top of the valve stem square on.

bigmockuk:
nursejulie thats my thoughts too,i was so sure it sounded like a very loose tappet,or damaged shaft,another member wrote about a 400cc having side movement at the tappets even though that bike has springs to help prevent sideways movement,up close,some of mine look nicely rounded off but others have slight imperfections,almost pitted,not sure if that could cause it.my tappets have a lot of sideways movement im thinking putting shims in there might help.im still positive its related to the rocker gear somehow.

Murf:
Well the engine is a bit noisy and has some rattling, it’s already been said but are you sure that the exhaust gaskets are not blowing a bit or even a bit of a blow on the cylinder head gasket.

At the moment we are all chasing shadows, so I feel you need to go back and systematically go through the problem. Every part of the engine has a specification  with a + and - tolerance, which is listed in workshop manual.  So you need to check the components which might create a top end rattle are within tolerance.  For example side float on the rockers has a tolerance listed, check them with a feeler gauge, if they are in tolerance then that’s not the problem.  If they need shimming then the difference between the listed specs and the actual gap will be the size of shim you need, you can’t make them tighter than the specified end float, or they will wear away at the head. You need to keep the rocker central to the valve stem, so need to know which side to put the shim, or do you need a half width shim on each side? 

What I would say is strip the top end then go through all the components:- bore wear, piston wear, piston ring wear, small end wear, big end wear,  all components related to camchain tensioner, cam lobe wear, cam bearing wear, engine valves, valve spring length, rocker shaft wear, rocker end float, worn or mushroomed tappits. Rebuild carefully , check engine timing, check ignition timing, put new spark plugs in. New gaskets and seals. Balance carbs. 

Then hopefully post video of beautiful sweet running engine 😄.
Well that should work but there ain’t no certainties with old engines.
BTW I am certain I will have missed something important from that list so please add.

bigmockuk:
Cheers for that Murf,its certainly in depth,and gives food for thought,im gonna step away for a few days n get some fresh perspective on things,i`ve got two bolts de-threaded now inside the top breather cover probably due to amount of times i`ve had it apart in last few weeks,so i`ll use thread inserts that i have to sort them.the bike is 48 year old but lay in a garage for 35 year so was only really on the road for like 13 year and covered around 25,000 miles,i would`nt expect to see any real wear n tear,it was running fine until recently then this noise developed so more sudden than gradual,it does have a loud clutch basket that i need to look into so the way ahead is to strip top half completely down n take measurements and renew all gaskets,do you know off hand where i could get a hold of shims thin enough i could use on side rockers? i`ll post back once i`ve had time to go through things and determine whats wrong and like you say,hopefully have it running sweet again soon  ;D

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