SOHC.co.uk Forums > CB500/550

sluggish 550

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matthewmosse:
Outside chance of kinked fuel line - a mate of mine who knows a lot more about bikes than me got foxed by the fuel line being just slightly kinked when the tank was fitted right - the problem was a right pain as in the garage it went away and only manifested itself out on the road where fuel demand got high enough for long enough. Lift the tank and all cured, put tank back on and only after a short drive would it go wrong again.

florence:
Are the throttle slides opening fully?

Are the choke flaps opening fully?

What colour are the plugs? 

Are all the downtubes hot after running?

mickwinf:
matthewmosse, will check but have tried different pipes, Florence, yes yes dont know yet, yes. Next thing i will swap the carbs for a spare set and see if that makes a difference.I still think it is a fuel issue, but i may have to start again with valve timing and compression checks,blast it !!

z1100r:
 I dont think its carbs...unless you have assembled them wrong in some way and the only thing that can cause this much of a problem is the slides...not opening or the wrong way round - cut out not at the back - or choke butterflys sticking. If your jets and everything are all std, and float heights let at least some petrol in and there is a reasonble flow from the tank it will certainly rev OK.

 This is a fundamental problem, posibly cam timing or ignition I reckon...most likely ignition. Is it std points and condensor..?? have you done the dark test..no sparks or ticking anywhere. Dodgy coils, bypass ignition and kill switch - just earth the black and white coil wires direct.
 try another ignition back plate with different point/condensors if you have one....look for lots of big sparks at one or other sets of points - little sparks OK.

 If you have to do cam timing again...take off lid turn engine to TDC1-4 and middle of slot in end of camshaft should be exactly parallel with the head face - with the tensioner working. Can be pointing either way, just needs to be parallel when at 1-4 on adv unit.

 After engine has run check tappets. I give up with feelers, all I do is TDC-1-4 and set 1(in/ex), 2(ex), 3(in), turn 360 to 1-4 again and set, 4(in/ex), 3(ex), 2(in). I think thats the right way round...but you get what I mean.
Job done.
 
I set them by undoing locknut and twiddling screw to touch valve, unwind 1/8 of a turn and lock-up. Thats good enough for me and how I've always done it for all 8 valves on my road engines or race engine.

mickwinf:
bad news, i tried another set of carbs but their condition is unknown although it did seem to rev better in first gear but ran badly so not conclusive.I thought i would recheck compressions and one cyl is down to 50 psi another is only 100 ish. Bugger

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