Leaky carbs, 1980 KS750 4cyl

Hello all, new to the site, great place. but to the point.

I've got a couple of questions, both carb related, to ask here.

1. I just got this bike, actually traded it for a '29 model A body and cowl, but it's having an issue with the carbs leaking when it runs. I haven't had it started much, but saw it when the other guys was showing me when we were trying to fix it before our trade (he's a good friend). After I got the bike I went to start it and the battery was dead. But, the carbs started leaking after setting the peccock to prime. My first thought is bad petcock, but any other advice is welcome. I've been looking for a petcock or a kit but all I find is for the 2cyl. I'm guessing they are different? I haven't found anything online yet to tell me that they're the same or different.

2. Possibly related, there is no airbox on this dog, and although I really like the looks of individuals, I also know the troubles that can come with them. I'm really more inclined to find an airbox and not mess with the tuning issues. Thoughts? I've been looking for an airbox and although I've run into one or two, I haven't bought one and they're not readily available that I can find. Any leads or thoughts otherwise would be great.

It's still got the stock exhaust also. And although I wouldn't mind finding a 4 into 1, I'm really all about putting it together to ride right now. I've got plenty of projects and just want something to ride. So that another reason making me lean more towards a stcok airbox as opposed to pods.

Thanks in advance for any help.

if the carbs are leaking it won't be the petcock it will be the float valve assemblys or in other words the needles and seats you can buy rebuild kits for your carbs that is probably why the airbox is missing. individual filters work fine contrary to some people i have never had any problem getting them to work your stock exhaust will be fine as long as its not rusted out as far as making the carbs work real well look a going to a dynojet kit it will make a huge difference if you set it up honestly (some people have a problem with being honest about the state of tune and riding ability) follow the directions to the letter and use really good filters not the emgos or cheap chinese knockoff's use k&n or ape filters they would be your best bet and the nice thing about the ape filters is they are reasonably priced do this after you have fixed your needles and seats. good luck and have fun with it.

I'm thinking typo in the title and KS750 = KZ750
Like TB33 says it's probably the float valves and seats. You can buy float valves singly. The float valves have little rubber tips which wear down. I replace mine every few years. Not expensive. On the Keihin CV34 carbs which is the original equipment you cant replace the seats but you can dip a Q tip in carb cleaner and run it around the inside of the seat to clean off crud. this insures a good fit and seal between the valve tip and the seat. If that dont work you can try the same with Brasso of some other metal polish. You would be best take the carbs off, drain and remove the bowls to do this. If you dont have an inline fuel filter you should get one. The tiniest bit of crud in the fuel line will stop the proper operation of the float valve

While you have the float bowls off you could see what size jets you have. If your eyes are like mine you will need a magnifying glass. If you decide to use individual pods you may need to get bigger jets. I have pods and never had problems. Just the way the bike came when I bought it.

Keep your eyes on ebay for an airbox. They come up quite often. Z1enterprises.com should have boots - the rubber connectors between carbs and airbox.

Regarding your petcock. see if it has 3 settings - Off, Prime and Reserve. Also look for a hose from petcock to a nipple on the #2 carb. If your setup is like this the you have a vacuum petcock and the normal position is Off. When the motor runs a vacuum via that hose I mentioned opens the petcock and allows gas to flow into the carbs throught the line that connects down low between carbs 2 & 3.

Hope all that makes sense

Right on guys, this is kind of what I was lookin for. Sorry I haven't been back sooner, but the holidays and everything, you know. And yes, it's a typo, it is a KZ, fat finger syndrome the other night.

First off, yes, I'm sure it has a three position petcock. I've talked with a couple of local guys about the issue and have a few other things to look at also.

The carbs have been rebuilt, supposedly. I knew the original owner, and he then sold it to a friend of mine, and then I aquired it. The first gy had the carbs gone through, and the the guy I got it from had them apart to double check everything. All that being said, I still need to get into them myself to make sure they're clean and the floats, needle and seats and everything look good. I'm sure I'll need a magnifying glass, ha ha...

Thanks for the input, these are kind of what I was looking for. Just a place to start. I haven
t been into a motorcycle for quite some time, and I'm really looking forward to having a scooter to ride again come spring.

Be sure to let us know how it works out..........and maybe post a few photos sometime

Hey, Run some seafoam through them. You might luck out. Roy