Ideal issues...

My 1980 kz650 is having some trouble idling..
Well running all together. I had the carbs rebuilt and synchronized and its still not rideable
I have a few ideas and a long lis of things to check but if theres something im missing that may let me skip to the riding portion i want to know

1. When it was hooked up to the carb sync you could see flames shoot up the tubes i know thats not normal
Possibly timing?

2. When the bike is running it is very hard to keep going it back fires alot and will not idle below 2,000rpm. I have mesed with the idle adjuster and no mater what u do it will not get below 2 and if it dose it shuts off. Sometimes it will completely shut off when it is reved out to about 4-5,000rpm.
Was thinking ignition coils might be bad.
Maybe the spark to the plugs is not strong enough.
Any thoughts or folks experiencing the same things?

If you have flames showing in the sync tool tubes your inlet valves must be open when the cylinder fires. If you had no air filter fitted you would see the flames come out the carb mouth. Neither of these are good.
Sounds like you need to do a FULL maintenance check on valve gap, valve timing, ignition timing, and carbs. Pretty much check everything before trying to start it.

I agree with Warren. And make sure the airbox is installed and sealed too. If you have modded the bike it will need to be rejetted.

Do you have the rubber caps on the sync ports? Ed

Yes i do.

Thank you Warren3200gt
Just had the values shimmed back to stock, carbs rebuilt. Only thing not stock is the exhaust and i did some research and everything i read said i would not need to rejet the carbs just adjust them.

And adding those to the list thank you!