sluggish 550

[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..!!

[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

[K2-K6]

That comment you made when you said "I thought I'd cracked it" what made you think the revs were better?

I ask because of this scenario:- if you start the motor, warm up and go on a ride at normal use then, IF the fuel supply is restricted it's possible that you've depleted the volume of petrol in the float chambers by doing this so that when you wind it up you get no revs increasing as fuel demand can't be met.

Soooo if you for example stop at roadside and turn it off, wait say 10mins (for the float chambers to fill)then restart and straight away nail it in first in theory while the carbs are full, then if it will get past 5000ish this would confirm supply problem and not timing of cam / ignition if that makes sense. If that's the case you need to strip and examine the whole supply pipes unions junctions etc to find it.

If you can't supply fuel at high enough rate then the simptoms can mimic very low float levels as the chambers will not be maintained at the expected level anyway.

It goes without saying that if you're not cnfident of cam timing you should verfy this as a priority.

[mickwinf]

i have checked fuel supply and is all clear,i thought it was fuel partly because it sometimes runs better than others.very fed up now will try again in a day or two thanks for all the advice guys,if anyone wants to discuss i can be contacted on 07870112945,cheers all, Mick

[SteveD CB500K0]

one cyl is down to 50 psi another is only 100 ish.

Are you sure? Can't have been finger trouble with the compression tester can it?

50 psi is on the lower side of bad.

Try again. Kill switch off, throttle wide open.

If low, pour a little oil into the plug hole and try again. A different (higher) reading indicates broken or stuck rings.

[K2-K6]

Aah, bit of a bummer! If it's cam timing I wonder what could be leading you the wrong way.

I think I was writing my last post as you were, so some of it's a bit out of sequence.

You should be able to measure an increase in valve clearance if you set them when they were all straight a bent one should now show a big gap to the tappet.

I'm sure you'll get there and eventually be able to get it going well.

[z1100r]

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

Well the thing is ....there is never just one valve down....if you clattered one you just have to have clattered the others. We have been talking fine tuning to resolve your problem, but you just have to have a more serious problem than that. I know how serious it can be... I've been there with a German guy and a 400 four in teh IOM. He was just trying to start his bike on the Kickstart and bent four valves seriously badly when his cam chain snapped whilst he was kicking it over. I put his four valves in a lathe borrowed in the IOM by the quay and straightened them for him just to get him home. He wrote mke a letter a year later thanking me and to say the bike was still going on the same valves.

The guy that built your engine originally needs shooting.