SOHC.co.uk Forums > CB500/550

sluggish 550

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K2-K6:
As the others say I'd try without the fuel filter to help understand it.

Also if you sit with it ticking over and then pull away and rev it in first will it run to the red line? if it does this on full float chambers then it would point to fuel supply volume being too low as well.

If you run it at 5000ish where it stops revving, then pull the clutch and use the kill switch, roll it to a stop and check the plug colour (otherwise known as a plug chop) it will give you an indicator as to to mixture at this point.

At the point at which it falters, try pulling the choke to see if it then revs higher and find out if it needs more fuel (wont work if there is insufficient fuel supply as above) but would help in analysis.

Try it without the air filter just to make sure it's not running you round in circles, it's not unknown.

mickwinf:
this afternoon i tried without filter,at first i thought i had cracked it, it seemed to rev better and respond to the throttle more eagerly,but again when i gave it some stick it falters at 5000 rpm at about 60 ish mph.So it does seem like fuel.Next i thought it could be the tap so i swapped it over, no change,removed air filter,the same in fact on the way home it started to run sicker at lower revs.it will rev a little more in first but reluctantly.I have checked brakes they are not seized i hope valves are ok compressions are good if choke on it runs worse.This is a real puzzle hope someone can help!!

K2-K6:
Very puzzling.

Presume you've got the tap on main tank? if so try it on reserve as it usually bypasses the longer feed pipe in the tank and if that is giving a restriction it would show.

Can you easily blow through the taps with your mouth as you should be able to.

You could try to set the static ignition timing to as much advance as you can get to assess that on a run out.

mickwinf:
tried on reserve no difference will try altering timing

z1100r:

 Something daft that I did once on 2-stroke was leave my bits of rag in the exhaust ports when put the exhausts back on. The rags got blown to the back of the pipes and caused me a fair bit of head scratching. That far back they dont burn away. Had to fish them out with very long lengths of welding wire. Caused a similar problem to yours.

clutching at straws now..!!

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