'04 Kawasaki KFX 700 idle problems from hard throttle to idle

I think Fixya Motorcycle Expert Gregg Mahin can answer this.

It would not really cause it. Back fire ( in the exhaust) are caused by:
- Fuelling to rich at low throttle. It could be the air screw setting, blocked air filter, wrong jet, floet level...
- Air leak on the exhaust (expecting you are using the standard system).
- If you are using a performance exhaust, try a baffle, a smaller pilot jet or playing with the air screw and idling screw. A slightly higher idling speed could cure it.
Tight valves could cause performance (especially when hot), difficulty to start and idle..'
Good luck, Franck

Trying changing the plug , if you didn't already see what type of condition it's in. Check to make sure you have spark. It may be your air screw need tunning.

is the carb jetted? if so check to make sure it has the right size jets. too small of jets starve the engine of fuel, and too large flood it. also there should be 2 jets one main jet which controls the amount of fuel when at 1/4 throttle to fuel throttle and then there should be a second which would be the pilot jet that controls idle mixture (1/4 throttle and less) it's longer and thinner than the main jet with multiple holes for mixing air and fuel for idle. have them to make sure the jetting is correct. Also IF the engine had been bored you will need to use larger jets for the added volume in the cylinder chamber from the boring. aftermarket exhausts will also cause the engine to be rejetted but usually the sellers will have charts telling you what jets to run with the exhaust.

If the problem is worse when warm then it may be rich.
try new oil, plugs and new air filter first.
also check for a flooding carb or leaking fuel tap, or bad diaphram in the fuel tap
clean the carbs, adjust the valves
if it still has problems then lower the needles 1 notch
keep notes on changes so you can change it back if there is no improvement or its worse

dyno jets may help if the jetting wrong or the exhaust has been altered from standard, but its not a miracle cure and wont help the starting on 3 cylnders problem which may be related

readjust carbs popping due to being to lean

It is in the carbs, A bike will act like that when it needs to be jetted, most jets are not adj, but whoever built the bike, must have messed with the carbs, you can go back to factory settings, which is about 1 1/4 turns out, and try it, you might need to get new jets, you might want to try dyno jet kit, they are adj and work great.. I had to do my bike, the exhaust was burning my eyes, backfired, wouldn't run, factory jets didn't work. But I found a dyno jet kit on ebay, and it works great. But before you take the carbs off, take a piece of heavy paper and cut the air intake in half with the paper to see what it does, then cut by 1/3, then 1/4, just to see if the intake is messing with you. Check it out, hope it helps.

if you had cam overlap then it wouldnt start and when you pushed the starter if would smash the valves together, if it runs ok every where else then i would say its a crab fuel problem and at that rev range it would be pilot jets as the mains dont come into use at that rev range you should take your bike to your local dyno center and have them run it up they will sort you problem

if your pilot jet is pluged it will not idle. the pilot jet controls fuel from o-1/8 throttle setting only