1978 KZ650 carb popping and backfire

Hi all.... i have been checking out the forum for a few weeks now and finally decided to post.
i got my 78' kz650 a few months ago, It has 4 pod filters and a kerker 4 into 1 exhaust. When I got it the bike would not start... after a few weeks I noticed that there were no lines connecting the #1 to #2 and #3 to #4 (not sure what these are but they are part #92059-141 #39 on some diagrams I have seen, I don't think they are fuel lines, maybe vacume???)They attach fittings between the carbs but the fittings are too close to squeeze a line between and I did not want to take the carbs off the rack so I cut fuel line and wrapped it around and used a clamp to tighten... the bike fired up and ran OK except the plugs would get deposits and run real rough after a few days... I then got 1 grade hotter plug, this helped a little but just delayed the deposits for a day or 2... About a week ago the bike starting running extra bad, popping out the carbs and cracking out the exhaust.... after running for a few miles like this I noticed the end cap on the #1 carb for the linkage was gone(located by choke control)... I made a new cap that looks to be sealing things up, I heard about a coil mod from Wired George, since the coils had 9v I did the mod, cleaned the carbs, put the original plugs back and fired it up.... It is still running bad...cracking and popping, even saw fire shoot out the #1 carb... I have a theory that I posed on another site, maybe someone here can tell me if I am crazy.... Could a mixture of low volts going into the coils and a series of vacume leaks in the carbs offset each other and have the bike run OK? (leaving only a vacume issue or just lean issue now that coils are over 12V) I plan to check the vacume leaks tonight... I am no mechanic... I have limited tools... I am hoping that this could be a vacume issue and maybe needing a larger jet, but not sure the jets effect idle....
I guess to get to the point... Anyone have a clue of what it could be?
I am in western PA, not sure if the exhaust has baffles... do not have the original airbox...
Sorry for the small novel, just trying to add as much info as possible.

Welcome.

I'm not sure what Part # 39 x 2 is.
Check the diagram below:

Do check for any air leaks around the manifolds.

I need to check for all leaks tonight....
i think 39 is some type of vacume line, when it was not connected the carbs were not delivering fuel and once I connected them they did, but I have never had fuel leak or shoot out before or after they were connected, these lines are in addition to the actual fuel lines between the carbs(where the fuel line connects to #2 or 3# carb, can't remember which one it is)
i am going to spray either starting fluid or wd40 around the carbs on the connections, boots, etc.. and see if it changes the idle (if I can get it to idle)Is either of these better than the other to use?
It really sounds bad:(

One more possibility????? Could I have burned out valves when running the bike with the cap off (maybe 20 miles or so toi get home).... I don't know if burned valves would cause popping or backfire....just a thought....
I am going home to check vac leaks..

hello, I have the same bike that I just went through all summer to get it right.IMHO dump the pod filters and get a stock airbox asap. you will never get it to run right with the pods in place. On my bike I have 2 hoses going to the fuel petcock. 1 is fuel the other is vacuum. with out the vacuum you will not get much fuel. sounds to me like you have vacuum leaks causing some of your problems.
you can pm me for more details as I have been working on that same bike and I'm very familiar with it. Bob

I will reply with more detail later, have to help my son...
Mike bike does not have the vac lin on the tank

sorry for the abreviated response...I think some bikes had vac lines from the tank and others di not, mine does not....
I have been considering the air box....
I started it up and noticed it runs better on full choke. I sprayed starting fluid on all vac lines, caps, etc.... no change to idle..is that a good way to test? i thought for sure I would find something...
I also noticed that the carbs pop more after I open the throttle past 1/8 turn (approx) an continue popping through high rpm's...Is this an indication that I need to either adjust the needle clip or get larger jets? How do I know what is in the bike now?
I really appreciate any and all help!
Thanks again

The #39 bits are vent hoses. The carb bowls must vent for the floats to work. There is a hole in the top of the bowl chamber in each carb. The #1 carb has a this hole which leads to an outlet on the side of the carb. This outlet joins to the adjacent #2 carb which has a similar outlet on the side (and passage to the bowl chamber) plus it has a brass fitting above the outlet to vent to the outside. Generally, a hose is fitted to the vent fitting so that if the bike overturns, the gas will pour out through the tube away from the hot engine. #3 and #4 work the same way. Since a vent is just a way to avoid a vacuum and the only real requirement is that the vent be open to the air, it makes no difference whether the #39 hose pieces are in place or not except in the event if the bike overturns and your pants are covered in gas and gas is covering the hot engine.

You found 9VDC when checking the coils. That would be your problem. Follow the simple directions given on our website for repowering your coils. At that point it will be easier to determine if the carburetors are working up to snuff. With only 9VDC at the coils the main problem you are having isn't the carburetors.

Thanks for the explanation on the carb connections....
I was not totally clear earlier.... When I started having the popping issues (and noticed the carb cap missing) I tested the coils and got 9V... I parked the bike in the garage, made a make-shift cap until I find/order an original, cleaned the carbs (off bike but on rack), and did the coil mod....The only thing I am not sure about with the coil mod is I got a 5 prong relay (with 87a) I read somewhere that this is fine but you need to reverse the 30 & 87 connections.... I hope that was correct info. because that is what I did. They are getting over 12v now and 0 with the kill switch off...
I am thinking that now that I have full coil power I am seeing more of the problems associated with the pods and kerker 4 into 1... I have no idea what jets I have, I plan on taking the carbs off again this weekend to check it out but not sure how to tell what is in there, is there a measurement to do or something that identifies the size. I don't know if they are stock or not, the pods & kerker were on the bike when I got it, don't know if they changed anything else when they were installed... just know it sounds like crap:( popping from pods (all of them) and exhaust, especially when rolling throttle, idles better at full choke, too much air/not enough gas, right?

Did you ever figure out what was going on with your bike? I have the same problem and can not figure it out.

He's been gone from the site for 5+ years. You probably should start a new thread. Ed