New guy with a new problem

Hello, glad to be a new member here from what I've read most of you are pretty knowledgable. I have a bit of a puzzle I am needing some help with. I own a '79 z650SR the top end was rebuilt and sat in a shed for a few years before I bought it. I had to put new coils and a battery in it right away but with a few kicks it fired up and ran(a little sluggish but pretty good considering) the original exhaust was a four into one and had the baffles cut out of the muffler(I assume he burnt a hole in the piston running lean explaining the low milage rebuild) the headers were also pretty beat up and restrictive. I was given a set of headers that have been cut off just after the second bend and installed them for a temp exhaust. I have individual pods for filters and have installed a stage 3 jet kit(#130 mains) when I fire the bike up I still have very sluggish performance and backfiring. I have checked ignition timing, cam timing, valves appear to function correctly. Will the cut off headers cause the valves to malfunction due to low/no back pressure? I'm a bit puzzled any suggestions are appreciated.

130 main jets are way to big. I have a highly modified KZ650 aand my carb settings are

Mains 118
idle jet 17.5
needle in middle slot
air screw turned out 1 1/2 turns
It runs great set up like that.

Man , It sounds like you opened a WHOLE can of worms ,,,,,

1) Are the pipes cut off so you have 4 open pipes ?

Don't even try to ride it like that .

When you get a good pipe on with NEW ex. gaskets ,
Then it's time to make sure your carbs are cleaned and adjusted right and sync'ed

Thanks for the replies, I just got my Mac 4/1 exhaust on and replaced my condensors(points were arcing everywhere) hasnt made a difference other than being quieter now. Still sounds like its firing on an open exhaust valve. Cam timing is correct, exhaust valves appear to be functioning although I assume incorrectly. I will put the 118 mains in. Sorry took so long to get back been workin nonstop on this thing, thanks again.

if you have a dyno jet kit for it don't be so quick to throw it out yet dyno jet mains are different than stock main jets 130 dyno jet mains might be just what it needs follow the kit instructions to the letter and also make sure that the pilot jets and circuits are completly clean spray carb cleaner thru them and the blow thru all the passages with compressed air it sort of sounds like you might have a dead hole at lower rpm's if the valves where a problem you could figure that out with a compression test pull out your plugs ground them against the head and then open the throttle wide open and crank the engine until the gauge stops moving relieve the pressure and move on to the next holes if the readings look low put a bit of oil about a table spoon will work and redo the test again. start there first find out the condition of the mechanicals before you move on to anything else. mechanicalthen carb then ignition. try it in that order that way you wont be chasing your tail all over the place. and driving yourself crazy. like you have been.

by the way welcome you have come to the right place grasshopper. :laugh: :laugh: :laugh:

Thank you, I do have a Dynajet kit installed. Im going to check the ignition timing again, not putting this engine together myself has made this a tough job. I have found the intake cam was off a tooth and a few other minor mistakes. I just finished reading my manual and I am suspicious of the ignition timing although I have checked it already I think it may be on the wrong mark "T" instead of "F". I dig your bike BTW.