Hi, Iv just purchased a z550f. They bike is running great in the lower rev range however once on the open road and high in the rev range it almost feels like the bike is starving for fuel.. I have put in a new fuel line and clean out the carbys but it still seems to be doing the same thing. I examined the vacuum diaphrams and they seem to be fine. The bike also seems to run better when cold in the higher revs.. The only other thing I can think of is raising the float level?
Any ideas or suggestions would be much appreciated.
Cheers
When you cleaned the carb, did you remove the jets? Sounds to me like the high speed jet is plugged
In some carbs, the needle controlling the slides have adjustable rings that a 'c-clip' goes into. You can usually unscrew the top main body of the card (Careful it's spring loaded as you will recall). You could check them to see if they're all in the same grove. I'm not sure that would solve your problem though??? A vacuume guage would make sure they're tuned correctly but it doesn't sound like tuning is the primary problem. How about the fuel petcock filter? Is it clean? Hose from fuel tank in good shape? That should take care of the fuel diagnosis, I wonder about the health of the CDI. If the fuel is fine and the spark is breaking down at higher rpm's the spark plugs will be more dark brownish. I suggest you clean or replace the plugs, take it out for a rip, Open it up to where it starts to nose over and loose power. Turn it off right then. Remove the plugs and inspect the colour. If they're a very light tan, you're running to lean (and out of fuel). If they're dark brown it's spark. I don't think the CDI box in your bike is servicable. Replace if you need to.
Best of luck, hope this was helpful
Bruce
Hi pjc135
I have recently bought a 1984 Z550f (aka ZR550 A2) which was running like a dog. I too stripped and cleaned the carbs, replaced the faulty coil, new HT leads and plug caps but also removed the horrible air filter box and replaced it with 4 small gauze cone filters. The engine then ran off choke, which it wouldn't before but as soon as you raised the revs it sounded like it was starved of fuel, even to the point that cylinder 4 wasn't firing, sparking but not firing?????
Turned out to be that my removing the air filter box was the cause of the high rev problems. The carbs were sucking in too much air & by cutting up a J cloth and covering the carb intakes with it, the bike ran like a dream. Hope this helps someone.
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Hey hgpilot,
Yes I cleaned out the main jets. I could see through them before I cleaned them so I don't think that they are the problem.. I removed the airbox the other day and examined the movement of the slides/needles in response to throttle position and revs. Two of the slides opened less that the others which makes me think it is the vacuum diaphrams but they look fine. Is there any other way you can adjust the movement of the slides/needles without changing the spring or diaphram?
Hey Bruce,
I solved the problem today. As you will know, most slides have a locating groove in them. This ensures that the hole in the bottom of the slide, which supplies the vacuum to diaphragm to lift the slide stays in its correct position in relation to the venturi. However the z550 carbys do not have this locating groove, the slides are locked in position via the diaphragm and due to old age they have come loose and have been spinning around freely which is why some slides have been opening more than others. I lined them all up manually and the bike went great on the open road. I will find some way to lock them in place permanently tomorrow. Thanks for the advice on how to check if the spark was breaking down I never knew you could do that simple check to distinguish between the two different problems.
Cheers
Pete
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