SOHC.co.uk Forums > CB500/550

CB550K3 carb balancing - the never-ending story

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Ashdowner:
Ok I'll take the screw out and check it. A mate has got a box of very small o rings so one may fit.

Ashdowner:
Just to bring this story to a reasonably happy end, and to admit that the problems I was having were entirely of my own making by not giving the bike a proper post-winter service. I got a compression tester and got awful results which suggested valve problems. I checked the tappets to find that the valve clearances had tightened and in the case of two valves completely disappeared  - so pot 3 certainly had a valve that wasn't closing. I redid the tappets and redid the comp test with much better results Pots 1, 2 & 4 around 110 lbs and pot 3 at 90lbs.  The lower compression on pot 3 I put down to the valve seat probably being burnt Anyhow, the bottom line is that the bike now ticks over very well at 1200rpm and over 3000rpm it pulls superbly without hesitating on the throttle and has that lovely singing noise. Even the clacking from the clutch has almost disappeared. Maybe I set the tappet clearances wrongly last time but it really brings home just how important it is to get them right. Next winter I'll take the head off and reseat the valves but for now it does everything a CB550 should do.

Trigger:
If the bike is run for sometime with the valves not fully closed, the valve face will burn and pit. This will also effect the valve seats, the valves will need re-dressing and valve seats cut to seal.

Ashdowner:
No doubt about it Trigger, but maybe I'll be lucky because it's hardly run since I last set (mis-set?) them. Anyhow I'll give an update when I pull it apart in a few months time.

Trigger:
Try setting them at 8 & 10, instead of 5 & 8.

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