Replaced Carb but bike still dies, what da heck

Hey all, new member but longtime lurker. Bought a 1980 KZ440 ltd last year and have been slowly trying to fix it up. Bought a new Mikuni VM34-168 and it has a one carb conversion. Also got a new Petcock as the vacuum one was not functioning right. Same problem still persists which is when i turn over the bike it really does not want to start. And on the off chance it does run it runs for about a second and then sputters and the carb makes a woosh sound when the bike dies. This happened on the old carb and now this one too. Not sure what it could be, maybe I have to tune the carb or rejet? Or electrical? Any and all advice would be appreciated.

Eddie

you say you bought a "new" VM34, that leads me to the following questions: 
 - is this an actual mikuni?  or is it one of the cheap knockoffs?

 - was it jetted specifically for your bike/setup?  or is it stock out of the box?

 - have you verified the fuel level is correct (if floats are set too low it can starve the engine of fuel)?

outside of that, have you checked the other things, like spark, compression, etc. ?

 

This will be helpful for diagnosis, maintenance and repair. Obviously the carb conversion is not covered, but all the factory stuff is.

www.kzrider.com/modules/ServiceManuals/kz440.pdf

Spark, compression and fuel are the ingredients needed to start the engine.  Verify fuel level. Verify spark. Verify compression.
If the engine did not run before, and converting to a single carburetor and a manual petcock did not solve the problem, perhaps carburetion was not the problem.

wrote:

And on the off chance it does run it runs for about a second and then sputters and the carb makes a woosh sound when the bike dies. This happened on the old carb and now this one too. Not sure what it could be, maybe I have to tune the carb or rejet?
 

If you have a problem with the carb, and you replace it with a brand new carb and still have the same problem, it's likely not the carb. You can try with some starter spray - if it fires properly and reliably with the spray, then it's likely fuel related. That could mean carb, but it could also mean old/bad fuel, blocked fuel filter or your idle/pilot settings are not dialed in.

Are you certain that 'whoosh' sound if coming from the carb? It could well be the starter clutch winding down, which I would describe more as a 'whir' than a 'whoosh'. Your carb shoudn't be doing any 'whooshing', at most a little 'put' if it backfires through the carb, which can be reasonably common if you're still tuning it or have a slow crank.

Hard to drill down on this one as it wasn't running before the carb change.
Just for the moment, let's assume it did and the engine is functional (timing is ok, etc.)
When it won't start and you get frustrated, it usually helps to go back to basics and get a bit of a plan, otherwise, you'll start throwing spanners! Bin' there!
This is an example of what I'd do. It assumes a number of things like the air passage is clear etc and will need modifying to your particular circumstances.
I've highlighted the three things I've found to be the most likely culprits.
The tools need are very simple and relatively cheap from eBay.
Even with a suspect carb, I'd expect to get it firing for a few seconds with easy start.
Once this can be established, then at least you can pursue the carb route as the source of the problem.
Google is your friend throughout this pain and anguish!
Good luck.1 Remove Tank. 2 Check petcock bowl for debris. 3 Set up temp' fuel supply with fresh fuel. 4 Ensure battery is fully charged and good. 5 Check voltage at Battery & coils. 6 check spark - Spark tester. 7 Remove and Inspect plugs - Colour and fuel. 8 Do compression test. 9 Replace plugs if required (likey need to). 10 Assuming spark good and fuel reaching plugs - 11 Try to start12. Use easy start if needed. 13 Assess which cylinders not functioning (cold). 14 Check for leaks -  spray carb cleaner. 15 Remove carbs - Full clean out. 16 Get choke plunger seals done. 17 Check/set vacuums

Check the valve clearances. 

Have you sealed off the vacuum feed(s) no longer required for the petcock?

Are you running any type of air filter?