Engine won't stay running; need help

ok, bike in question is a 76 KZ900. 11k miles. Hasn't been run in 20 to 25 years. Garage kept always.

My dad gave me this bike. He's the original owner. We started getting this bike back up and running by taking the gas tank off and red coating it. Changed some seals that were in bad shape along the way. removed the spark plugs, checked for spark. Spark was there. Air cleaner looks brand new. Put new gas in and tried starting it. Nothing.

So today I pulled off the carburetors and cleaned them out. Flipped them over, removed the bottom bowls, took the jets and what not out, cleaned with carb cleaner, shot air through everything with the air hose, put it all back together and put them back on the bike. It now runs, but only with the choke on.

If I keep the choke in just the right place, it will stay running and sounds pretty good, except for idling high. if I idle it lower, it will still run, but as soon as I hit the throttle, it will die. Regardless, using the throttle is hit and miss it seems.
The exhaust is in really bad shape. It's there, but the pipes are pretty rusted and holy. A guy I work with said the pipes can cause problems if they're in bad shape and that I should replace them before getting to carried away with other things. Is he right?

So I'm looking for any help to get me up and running. I'm dying to be riding this bike rather than working on it. Not that I mind working on it.

I know exhaust will change how you need to jet it , but I don't know anything more. I don't know if this would help any, but a simple test might be to wrap the holes in the exhaust with aluminum foil or something similar as a test. If they are small holes I don't think it is the problem.

Have you checked the valves? My brothers honda had a similar problem, it would run on the choke barely and if you hit the gas it would die. The exhaust valves were too tight. It's maintenance anyway so it probably wouldn't hurt to check it.

The pilots are very small. Use a guitar string or a strand from a wire brush to clear them. Also check the valve clearances. If too tight DON'T run it until corrected.
Steve

I used a wire from a wire brush to clean the jets. I haven't touched the valves yet. I guess that's the next things I need to look at.

You're the second person to suggest valves. So I guess that will be the next thing I look at.

No eBay APP ID and/or Cert ID defined in Kunena configurationThe most neglected because it costs money or they were too lazy to do them.
Steve

This is where I'm getting mine.

Awesome, thank you. I was planning to get the Vance and Hines 4-1 exhaust at some point to replace the ratty one on there now. Eventually going with a 4-2. I also plan to get the K&N air filters that replace the factory airbox. It sounds like each of these will change how the carbs needs to be jetted. Is there a way to precalculate what changes the carbs will need with each upgrade? Will these changes require any other modifications? I'm not looking for this bike to be a street sleeper or anything like that. I just want it to be dependable.

Then keep the airbox. Pics of the bike?
Steve

Here you go. I've tried posting pics several times, but I'm always on my phone. Tonight I'm on my laptop. WAY easier.

You can get a pare of slip ons for it. I think I've seen this before.
Steve

Congrats on the Project. It's nice to see a KZ back in the day light. One of the first things you should get is a Factory Service Manuel. Fortunately you can down load one from this website A valve clearance check is in order because it will affect about everything you are trying to do. Fortunately there is a carburetor cleaning guide on the forum too. There are a bunch of a bunch of guys from all over that know their stuff and will direct you down the right path to get the old KZ back on the road.

It'll run without any exhaust on it so no the exhaust wouldnt give the symtoms your seeing. I would say that your fuel passages are not clean enough. I think you still have partial blockages in the carbs.