sloppy starting

[JoeZXR]

IV had this problem since iv had my bike and a few of my friends have it with there zxr 400s too..

its not that the bikes dont start, they fire up almost everytime, but they seem to be very sloppy and have trouble starting without a blip of the throttle...

most of the time i have to turn my lights off to give the battery a bit more power, the starter motor turns over fine and even with a charged battery i have the same problem, i just seem to be constantly having to hold the starter buttom for about 10 seconds until i finally get some sign of ignition then i give it a blip of the throttle and it fires up sloppy and slowly build up the revs, this is from cold but from hot it fires up and idles nicer and quicker but still takes atleast 10 seconds of turning over.. its almost as if its starving then all of a sudden fuel finally gets chucked in.

my friend has been trying to solve it for a long time but cannot fix it, where as i just get over it and carry on with holding the starter button lol

but iv always wondered do all these bikes do this? or is there a way around it?

[ross46]

My bike starts fine, almost instantly, only needed about 3 seconds in the winter (-5!) sounds like a fuel problem, is the fuel pump working ok? i would check air, fuel and spark. Is the pilot mixture set ok? Does it run ok at low revs when running? If not then try the pilot screws. Work through everything one piece at a time, eliminating things as you go but i would start with fuel

[banner001]

you need 4 things:-
fuel
air
ignition
compression

get a compression and leak-down test performed on the head so you can check for sufficient compression.

im gonna lap my valves at some point, im sure thats the cause of most peoples ignition problems, small losses in compression and loss of fuel vapour from the cylinders at startup leading to difficulty firing up.

if you know that your head is in good condition, valve clearances correct, good compression, fuel mixture correct, good spark...THEN you have a problem

[JoeZXR]

haha well lets just put it this way, my bike runs great and the compression cant be too bad seeing as it still puts out about 135mph

as for fuel and air and everything, literally everything has been cleaned and all fuel lines replaced, all air leaks sealed... carb balanced, everything is set up top notch now the only thing iv not changed on the bike is the engine internals, iv heard lots about zxrs always being crappy at starting thats why i asked just to see if it was true

i dont know if this would be realated, but iv been told this is normal for most 400cc older bikes, until i enter my powerband area past about 4k revs, anything under 4k is boggy as hell, but iv been told under 4k revs is just the slow pace rev range so wrapping the throttle back under 4k will bog down on most bikes and so far i have not questioned this because after 4k i have no flats spots throughout the whole rev range or anything.

i can still crawl in 30mph area and traffic under 4k just with a tiny bit of throttle fine though

[RedexRobB]

Zxrs are renound for poor starting when the battery isnt tip top. Other things to look at are the plugs properly gapped and clean? Are the valve clearances ok?