I have a 2000 cbr600f4 it runs smoothly in low rpm but when it gets up to about 5000 rpm it shudders for a second then picks up anyone know what this could be is it the jets?

 

that sounds like what most people would describe as a "flat spot" in the throttle. when is the last time you changed your air filter? how do your spark plugs look?

 

The air filter looks good still i changed the spark plugs but they were not the same brand they were cheaper spark plugs would it effect it that much ?

 

did you start having the problem after you changed the spark plugs? or did you change the plugs to hopefully fix the problem? I'm leaning towards carbs.

 

There is mid-range reversion phenomenon from Helmholz resonance in intake (pressure-pulses moving in and out of engine). In mid-range at certain RPMs that actually pushes air backwards out of intake. This causes triple-caburetion of fuel, once on way in, once reversion pulse goes out, and another time when that same air goes back in. Resulting in way too much petrol and you get stumble.

You can test this by richening out mid-range mixtures slightly by shimming needles up with one washer. If it makes it worse, problem is mid-range triple-carburetion problem. If it makes it better, you've got clogged dirty carbs that need cleaning.

 

wouldn't shimming the needles up richen the mixture?

 

True, sorry I got it mixed up. Fixed my post. Thx.

 

I e been learning as I go with my first bike ever,and I'm almost done,I'm actually about to put new oil, antifreeze in her, hopefully all the new gaskets I've installed and a temporary high torque gasket maker won't see anymore leaks.but my main issue is the two black plastic RAM air ducts that go from each side of headlight back into the air intake box,there are tighteners that's supposed to keep them from coming out,but I've had them as tight they could go,and still the plastic ducts are loose,
Any ideas on some kind of modifications or what I should do, please.

 

trust me, you will never be "done" as these are always requiring maintenance and work.



what did you put gasket sealer on? be very careful when applying it. if you use too much, it can squish into the engine, come loose over time and clog up passages in the engine.



sounds to me like the threaded clips/inserts are stripped or the fasteners are too long and not bottoming out. there are still a LOT of parts available from the factory if you need anything. I personally use www.RonAyers.com. They also have the bike broken down into subsections with very detailed parts diagrams. if you can, post some photos of what you are working with and maybe someone will be able to help you better.