Engine backfires

I Recently bought this ltd 440 and got it running it’s my first motorcycle I’ve owned and worked on. carbs have been gone through and cleaned with ultrasonic and the engine backfires I can feel it popping in the carb, the engine picks up in rpm when I choke it. I checked and set the valves to .127mm thought maybe a vacuum leak and it picks up in rpm when I spray ether near the boots and spark plugs. I am looking for help on this and am stumped hopefully one of you can help me with this issue

If the ether causes the rpm to rise, that is a sign of significant leaks around the carb holders. If the rubber is hard and cracked, they need to be replaced. 

Would this cause backfiring in the carbs? Also curious why the same thing happens around the spark plugs which were just replaced

The ether should have no effect at all on the outside of the plugs. I suspect that it is being drawn into the intake tract. Also check to be sure that the carbs are fully seated in their holders. If not, they can leak like crazy. Also check the vacuum line from the petcock and that the vacuum port on the other carb is securely capped.

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Would this cause backfiring in the carbs? Also curious why the same thing happens around the spark plugs which were just replaced

Are you 100% sure that you haven't cross threaded the plugs and that the sealing washers from the old plugs didn't get left behind ?

Yeah I double checked all that and it threads in nicely

I can only think of a cracked head if your experiencing a backfire at a spark plug. If as you say they thread in and seal correctly.

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I can only think of a cracked head if your experiencing a backfire at a spark plug. If as you say they thread in and seal correctly.

Is the head heavily corroded around the plugs (this could stop them sealing)

Cracked and leaking carb boots have caused me  spit back/backfire through the carbs noticeable at low rpm and idle.

Does your bike have one of those clear air systems connecting the airbox to the cylinder head ? If so then might be something going on there also with the ether

 

After waiting a long time for parts I put in a new vacuum slide and boots and it sounds better running other than the timing it takes a lot of effort to get it to run and it sounds like the timing is slightly off if anyone can refer me to a maintenance check/procedure 

Timing is on pages 18 - 20. All the maintenance procedures are in the manual.

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

The maintenance chart is on page 16. I highly recommend doing all of it.