Bike Dies

[Why Z?]

Just got the bike. Had 5 miles on a brand new complete rebuild when first bought it.
My confidence and trust in the person who did the work is pretty high. He is (and verified to be) a mech for a major power sports company and former gasgas rider/racer.


Not long after getting the bike home, at about 30 miles I started to experience some hard starting and the bike has died a few times on decel, normally after being at cruising speed and then shifting down (and having clutch pulled in) a couple times the engine has just cut out completely.
Then usually has started back up, sometimes with 2-3 pushes of the button.

Details:
Hard starting -
-usually when started for the 1st time of that day. (Doesn't have difficulty when it is started after being shut off for only a few hrs).
-temps : Normal 50-65 degree weather cond.
- usually emits a "POP" on one of the failed starts.
- seems to help if I kick over a couple times (which have never successfully kick started the bike )
- kicking: never successfully kicked this bike to life. (Yes I am lil 120 lbs but have had no issue kicking a wr450f and yz250fs, this one doesn't wanna kick --- my dad who is almost 200 lbs couldn't kick it either)


Any ideas/suggestions ?

Edit: I LOVe LOVE LOVe this bike. If there is a problem I can correct I want to do it right away, because this is THE BIKe of my dreams... But I don't want to lose confidence....

[phoenix]

Which bike do you have? 4 stroke? Almost sounds like something (like a rag) is lodged in your airbox or your choke is stuck on or something like that. Might look at the easy little things like that that may have been overlooked on reassembly.

[Why Z?]

07 450 FSR (4 stroke).

I took the air filter out and checked it and put some more oil on it and put some grease on it while I waited for my new one to come in.

The original air filter seemed to fit not quite right I must say.
Having had a KX 100 and YZ250f before this for MX, I am no stranger to air filters cleaning them and putting them back in.

On this one before the filter had much dirt at all I put some extra oil and a bunch of grease (note: Li ion - didn't like it as much as amsoil poly red)
Also I have always greased my filters in the past - (the poly red stuff) and never had any issue. However with this bike it was trickier on this bike with everything being pretty tight w the battery etc.

I took great pains to make sure the filter was seated on there correctly,
It was a lot tougher to determine than on my Yzs and KX ,

Also, one reason I did this is I was just not super confident in the seal and Fitment . Original (Twinair) filter seemed to fit not so good (skinny coverage to one side) and lack of grease/substantial oil .

NOTE: bike does not always die, nor does it do it so often I can't get anywhere.... It is just kind of unnerving especially when it does this in traffic, or conversely when way out in the bush! Usually has died within first 5 mins or so of operation too when it does this . No other adverse effects observed ; it is very powerful throughout

[bergerhag]

You are certainly not the first to experience this. Read through some of the threads i the Engine 4-stroke forum section. Lots of useful info there.

[Why Z?]

That's not what I wanted to hear after just buying the bike ... A persistent model specific issue.... :-( :-(
Well thanks for being honest and pointing me in the right direction

[GasGasDreamer]

i have had some crazy symptoms caused by the gas tank vent tube.
i just throw that thing away and run a long tube.
the other is a sparkplug gets really weird if the air fuel mixture screw is adjusted with the bike running.
so i would suggest a simple vent tube without any check valves and a new plug