Poor performance

so i just picked up a 1983 kz550 ltd, bought it from an older guy with 7500 miles on the motor. When I picked it up it was super peppy had a lot of power for a 550 and I rode it home on the highway around 80 mph. I own a t stroke repair shop but I have t had a 4 stroke motorcycle in almost 8 years, I had it for a day or so befor I found the crack in exhaust cross pipe looked like it had fallen over nothing major I welded the cracks, since then it seems like the power is getting worse and worse, I've changed the oil and cleaned and bench synced the carbs and put fresh plugs in it. But I doset have that same off the line power it had when I picked it up and if I try and open up full throttle it Boggs out bad and backfires. It seems like it's running very hot. I tried to check the timing but it is cdi and looks fixed and I hit it with my timing light and it is on point, the auto advance opens up at 3000 rpm also, I'm not sure where I should go from here it seems like it's a air fuel issue with the backfire but also a timing issue with the loss of power. Any help would be greatly appreciated I just need to find out where to start

Clean fuel tank/petcock assembly? Then install filters. Next check fuel levels with clear tube. May need to clean carbs. As a first step, you could run some Gumout or Sea Foam through the gas.

Roblogan wrote: if I try and open up full throttle it Boggs out bad and backfires. It seems like it's running very hot

very hot usually means lean. I wonder if you have some crud blocking a main jet.

What is used for air filtration? By any chance did you remove the air filter or air box? Ed

I took out the carbs and cleaned them bodies float needle, jets and all, blew them all out with cleaner and compressed air just like I do on all of my carbs. The tip of the plugs were realy light when I changed them it does seem like it's running lean, but I'm running the stock jets and air box that I had when I got the bike

Is there anyway it could be a timing issue being advanced? When is the advancer soposed to open because at 3000 rpm is when it was opening up with my timing light

Stock everything haven't changed anything or modded anything just the usual carb clean tank clean and oil change I do with all my bikes but I havent worked on a 4 stroke in a very long time just 2 stroke bikes

The advancer may be sticking? Take it apart, clean, and lube it. Ed

i was thinking that i would take apart and clean the advancer, its just strange that the power loss is happening after i do just routine maintenance on the bike. it is very noticeable once it is warmed up and off choke and im in any gear under load and i try and open it up just just studders and back fires i have to roll on the throttle pretty gently. i know it had alot more power than it has now im just trying to get to the bottom of it. possible that im running lean my plugs were very light even after the carb cleaning with stock box and filter, i may end up jut rebuilding the carbs. also to check the fuel level in the bowls with the clear tubing how are you going about this test?

The images below show the basics of the clear tube fuel level test. Ed

Check your valve adjustments.
Steve

Before checking the valves, read the vale train warning in my signature to prevent possible damage.