SOHC.co.uk Forums > CB500/550
Top End Build Help!
Neilw:
I've been rebuilding the Top end on my CB550, and it's not been without its challenges, but I have the rocker cover on now and am now attempting to set the valve clearances.
Quick back story - I had the top end bored out and new pistons and rings - which all went back together again quite nicely. The cam chain was another story, but I got there in the end. I had previous revoved all the valves, lapped them and reinstalled, including new seals.
When i installed the rocker cover, I loosened all of the valves to make it easier to get on; now I'm at the point of trying to find TDC. The video i'm following is pretty straightforward, but assumes you already have clearances that work, so you can identify whether 1 or 4 is on its compression stroke, so that you know you have the cam in the right position - hope i explained that correctly. Anyway, an alternative method was to put your thumb over the park plug hole of no 4, so you could feel the compression. This is where I'm having trouble - in fact I have two areas of concern
When I turn the engine over using a spanner, I get a loud snap back from one of the valve springs - could this be because of the slackened clearances? I can get it to happen on other valves by screwing in/out the adjuster. OR is there something more sinsiter going on?
How do I approach doing the valve clearences - is there something i can do to "reset" the clearences so i can work out if 1 or 4 is on the compression stroke?
Also, and i don't have a good feeling on this one - when i put my thumb over the spark plug hole for No.4, i got no compression or feeling of pressure, but i did when i repeated the process on No 1.
I guess i need to sort out the value clearences so i can see if that sorts out the snap back noise and also allow me to put a kick starter on, so i can test the compression properly.
It's quite possible i haven't installed somthing correctly, I'm new to this, but have been very careful as i've put the head together.
Any help or advice is greatly received - I'm just at a loss of how to proceed and need to clear thinkers to help me :-)
Many thanks in anticpation.
Bryanj:
A loud snap is worrying as it usually means a bent valve that is sticking in the valve.
Loosening all the clearances is simply NOT ENOUGH when refitting the cam cover, you have to hold all the adjuster ends up(rubber band trick) to make sure the followers are on the lobes so that the adjuster end can not get jammed on thetop of the valve stem and push against it bending the stem.
To set clearances you have to have the T 1-4 mark lined up with the static mark, at this point the lobes of the cam on either 1 or 4 will be pointing down, this is the one on compression, after setting turn crank CLOCKWISE 360 degrees and set the other cylinder, same for 2 and 3.
I hope you have not bent a valve but it does sound like it
Johnwebley:
Refitting the 500/550 rocker cover needs some care
Ideally 4 rubber bands holding each cylinder rockers up from the valves
This is to stop the tappets bending the valve stems
When setting the clearance, 1-4 should be at tdc,just set the cylinder with the closed valves, then rotate one 360 degrees
2-3 are 180 from 1-4
Sent from my SM-A546E using Tapatalk
Neilw:
--- Quote from: Bryanj on August 03, 2026, 07:36:59 PM ---A loud snap is worrying as it usually means a bent valve that is sticking in the valve.
Loosening all the clearances is simply NOT ENOUGH when refitting the cam cover, you have to hold all the adjuster ends up(rubber band trick) to make sure the followers are on the lobes so that the adjuster end can not get jammed on thetop of the valve stem and push against it bending the stem.
To set clearances you have to have the T 1-4 mark lined up with the static mark, at this point the lobes of the cam on either 1 or 4 will be pointing down, this is the one on compression, after setting turn crank CLOCKWISE 360 degrees and set the other cylinder, same for 2 and 3.
I hope you have not bent a valve but it does sound like it
--- End quote ---
Oh S**t, that doesn't sound good.
So next step is to remove the head and check the valves, then go from there. If the valves are bent, could there be any other damage I shoud look out for?
Otis:
Do you have this or similar?
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