Starting a rusty '82 KZ750

Are you sure that two of the floats are not installed upside down?

TexasKZ wrote: Are you sure that two of the floats are not installed upside down?

Thanks Tex. Unfortunately yes. They are oriented properly. Should I just get two rebuild kits and hope that will solve it? I just don't know what else I can try.

Not much doing at this point. I've got a severe case of tendinitis in my arm they just shot up with cortisone. But I was able to measure current float height:
1 = 21.8
2 = 21.5
3 = 19.3
4 = 20.6

Also I have cleaned the seats and hosed out that all out with carb cleaner.

Ok. Made a stand for the carbs so I could verify the fuel height when on the bench. The float heights listed below corresponded with the fuel levels as you would expect. With the lower float heights of 3 and 4 those bowls had higher fuel levels. So what's happening when the carbs are on the bike (on its center stand)? I just don't know.

You might want to check the petcock to be sure fuel isn't back flowing down the vacuum line.

Nessism wrote: You might want to check the petcock to be sure fuel isn't back flowing down the vacuum line.

No petcock in use. Using a aux tank made from a water bottle. Gravity flow

The inconsistency continues. Readjusted the floats back to 21.5mm (all floats are now about that height). Put the carbs back on the bike. She fired up. Idling. All four headers are hot... again. I'll let it rest for the night and see if it'll still be cooperative in the morning. She's done this before, not getting my hopes up.

UPDATE: Woke up and the first thing I did was start the bike. It started and idled. Header on #4 is not as hot as the rest but it is still hot at least. Keeping fingers crossed I can sync it up and all will be well with the world.

Tvag06 wrote: The inconsistency continues. Readjusted the floats back to 21.5mm (all floats are now about that height). Put the carbs back on the bike. She fired up. Idling. All for headers are hot... Again. I'll let it rest for the night and see if it'll still be cooperative in the morning. She's done this before, not getting my hopes up.

If you have it idling I would take it out for a ride and run some fuel through it. That way you can get all the crap cleared out of the engine from all those cold starts and idling.

Oldjeep wrote:

Tvag06 wrote: The inconsistency continues. Readjusted the floats back to 21.5mm (all floats are now about that height). Put the carbs back on the bike. She fired up. Idling. All for headers are hot... Again. I'll let it rest for the night and see if it'll still be cooperative in the morning. She's done this before, not getting my hopes up.

If you have it idling I would take it out for a ride and run some fuel through it. That way you can get all the crap cleared out of the engine from all those cold starts and idling.

Even with the backfire in #1? I was reading about removing air suction system and running just a hose between the two reed valve covers and plugging the hole in the air box. That seemed to solve some folks backfiring issues but IDK if their bikes were backfiring while idling.

Tvag06 wrote:

Oldjeep wrote:

Tvag06 wrote: The inconsistency continues. Readjusted the floats back to 21.5mm (all floats are now about that height). Put the carbs back on the bike. She fired up. Idling. All for headers are hot... Again. I'll let it rest for the night and see if it'll still be cooperative in the morning. She's done this before, not getting my hopes up.

If you have it idling I would take it out for a ride and run some fuel through it. That way you can get all the crap cleared out of the engine from all those cold starts and idling.

Even with the backfire in #1? I was reading about removing air suction system and running just a hose between the two reed valve covers and plugging the hole in the air box. That seemed to solve some folks backfiring issues but IDK if their bikes were backfiring while idling.

I wouldn't trust anything an engine is doing when you keep cold starting it and letting it idle for a little while

I seriously doubt that the clean air system is the problem. Its sole purpose is to introduce clean, filtered air into the exhaust ports in order to dilute the exhaust gasses so the bike can pass an EPA sniffer test. The most common malfunction is for the vacuum hoses to split, causing two cylinders to have a lean mixture. That doesn't sound like your problem.
Back firing (firing back into the carburetor) is most often the result of spark plug wires connected to the wrong plugs, or an intake valve not closing.
After firing (into the exhaust system) is he result of raw fuel entering the exhaust system and being ignited. A flooding carburetor or an intermittent or completely absent spark can cause this. So can suddenly closing the throttle, though this is rarely heard with a stock exhaust system.

TexasKZ wrote: I seriously doubt that the clean air system is the problem. Its sole purpose is to introduce clean, filtered air into the exhaust ports in order to dilute the exhaust gasses so the bike can pass an EPA sniffer test. The most common malfunction is for the vacuum hoses to split, causing two cylinders to have a lean mixture. That doesn't sound like your problem.
Back firing (firing back into the carburetor) is most often the result of spark plug wires connected to the wrong plugs, or an intake valve not closing.
After firing (into the exhaust system) is he result of raw fuel entering the exhaust system and being ignited. A flooding carburetor or an intermittent or completely absent spark can cause this. So can suddenly closing the throttle, though this is rarely heard with a stock exhaust system.

While I would normally agree with you, I seriously doubt the clean air system is... well... clean and functioning properly. I ended up removing the system, connecting the two Reed valves with hose and put a stopper in the airbox and... Backfire actually did stop. Haven't heard but one since. Ended up checking tires, chain tension, lights, brakes, etc and took it for a 5 minute spin with no tank! Just the tiny aux tank I made hanging off the handle bars! Lol I can't imagine what the dog walkers thought of that sight.

I'll try for a carb sync tomorrow and see if I can't get that #4 to pull it's share of the load. It's still cooler than all the rest. I'll also rinse out the temp has tank and inspect the petcock I cleaned before. Get them ready to mount