hard to start, backfiring, rough idle

Hello again everyone.. I got my 80' kz750h Four a month or so ago, was running good until a few days ago.. I ran the recommended amount of seafoam through it because it sat for a year or so before I bought it, seemed to run better afterwards.. Few days ago I took it to work and halfway there my fuel light came on.. After work It had a little trouble starting but it started and I got home.. Few days went by without running it from being busy.. Today I finally got my original handlebars in the mail and a fuel filter.. Pulled everything off the old handlebars put on the new handlebars and put everything back on them, went and got some 93 octane gas and filled her up.. Haven't put the fuel filter on yet because I wanted to start it and turn the petcock off and get most of the fuel out of the lines.. Try to start it and it wouldn't turn over.. After a few attempts i got it to start, but it was real rough and sounded quite odd compared to normal, and was popping and backfiring.. If i gave it any blip of the throttle it would try to die/ or die.. Let it sit awhile tried again and same thing with louder backfiring.. Gave up for the day but was looking for any input? if it was real low on gas could it be a bad mixture of seafoam/fuel that its trying to start with? Should have pulled the plugs to see if fouled but didn't think of it ( hot and humid today ready to relax) .. Just thought it was weird it was running fine and now it's messing with me .. well , thanks for any input given!

Maybe the seafoam broke some junk loose and then got sucked into the starter jets, pilot jets/ circuits. Try disassembling and cleaning the carbs real good. Don't forget to clean the tank to.

thanks for the reply.. I've been wanting to take carbs apart and clean them ( the guy i bought it from said he did but who knows) but i've never done it and wouldn't know where to begin.. I was hoping I could get through this summer how it is and during the winter tear it apart and try to figure it all out.. Took the 2 outer spark plugs out after work and they were fouled so im going to buy some new ones.. thanks again

If you decide to take the carbs apart be sure to keep each carbs parts separate from the others. Don't mix parts between carbs as that can lead to problems (parts wear together). Using 4 plastic containers, 1one for each carb, works well. Ed

If the bike sat for 2 years with the old gas in the carb then they will need cleaning. I am suprised you got it running at all.

Yeah i was suprised it fired right up as well.. and thanks for the tips ed.. The guy said he had cleaned them so maybe thats why it fired up.. But who knows.. pulled all my plugs, 3 of 4 were fouled, and while tinkering around it seemed like the seafoam knocked some stuff loose and it clogged up my fuel filter.. Put new fuel filter in, got new plugs today and had battery on charger, put new plugs in and battery back in and fired right up.. I'd be more comfortable giving my carbs to a shop to clean them , but there's no shops anywhere near here .. I guess this winter will be a learning experience, or an expensive mistake hahaha.. thanks

Why do you need a shop just do it yourself, not really hard, just be methodical and take your time.

yea i've just never messed with carbs and would feel more comfortable with someone that knows what they're doing to do it.. But yeah most likely will myself during winter