Gpz550 can't accelerate at full throttle

I recently bought this bike from a friend who says it has a stage 3 jet kit made by dynojet. The bike starts and idles fine but when I go full throttle the engine only accelerates to about 6k rpm and won't accelerate anymore unless I drop back to about 1/2 throttle. When I checked the plugs the right two (when you're on the seat) were pitch black (rich) and the left two were really dry looking (lean).
I took the carbs off, looked inside the float bowls and found something weird that I'm not sure is related to my problem. The left two carbs have an orange looking plug in them [pictures below] and the right two don't.
I tried removing the plugs and running the bike but it couldn't rev past 7k on the stand like that. So I put the plugs back in. Can anyone help with my problem? Also what are those plugs and how come I only have two? Thanks guys.

There should be another jet under those covers. The covers are there to prevent the jet from getting fuel from the bowl directly. They get fuel from another passage. You should have 4 of them.

I assume you have an 82 or 83 KZ550H (Gpz)? Is that correct? I think those were the only 550 gpz years that had those plugs. Basically you just need something to seal off those openings that won't disintegrate in fuel. Also, they should not go so far into the hole that they get near the jet.

A small round lead fish line weight might work, pressed into the hole.

Good Fortune!

sounds just like a battery with a dead cell to me...exactly like it...imo

vector86 wrote:

...starts and idles fine but when I go full throttle the engine only accelerates to about 6k rpm and won't accelerate anymore unless I drop back to about 1/2 throttle....

If not already done, would assure correct ignition timing using a strobe type timing light, and assure proper functioning of the advancer by watching it move quickly back and forth as rpm is varied by blipping the throttle.

Good Fortune!

check the slides to see if they arf moving freely up and returning on their own and evenly it sounds to me like a diaphram problem also what kind of air filters are you using. c.v carbs can quite finicky about filters or lack of