does anyone know if they fixed the problem with starting when the motor is hot?And another question is, I've read in the pipe shoot outs for the'01 250F the pipes was a big improvement from the stock pipe is the stock pipe really that bad.
there's no "problem" starting the yz250f hot or cold. i don't know where this "yama's 4 strokes are hard to start" myth got going but i've got an '01wr250f and my brother has the '01yz250f -- both start on the 1st or 2nd kick, hot or cold. in fact i rarely use the hot start button. a couple of weeks ago, there was a guy and his (140lb) 15 year old parked next to us at the track. the kid was already riding a yz250 but he and his dad were real interested in the yz250f. i gave the 15 year old thirty seconds of instruction and he started the 250f on the first kick, hot.
if you take 5 minutes out of your life to a) learn the "drill" and b) adjust the fuel screw correctly, these 250f's will light right up. many many wr's have needed fuel screw tweaks -- they are shipped from yama too rich. an easy test for this is whether the bike starts easier cold with the hot start button pulled out (the hot start button leans the mixture by introducing more air). if it does start easier, well, you need to adjust the fuel screw IN (=UP, since it's upside down on the bottom of the carb).
after my fuel screw adjustment, there have only been maybe two occasions which required more than 2-3 kicks to get it going. on one occasion i bit hard in some ugly sandy whoops, and the bike was on it's side for more than a minute while i shook the stars out of my head. in these cases, if it doesn't start on the 2nd or 3rd kick, i go into "clear it out mode", pull the decompression lever, and kick it through about 5-6 times. then restart "the drill" and it's alive.
the stock pipe is good. not great, but good. all these shootouts cater to the advertisers-- i don't think that there is more than a 1-3% difference in performance with any of these pipes compared to stock. of course, on a two stroke, the geometry of the pipe is everything, since the engine relies on the pipe for proper combustion chamber scavenging. but on a four stroke there is much much less dependency on pipe geometry. there's no "quick" 10% gain and you certainly can't "move" the power around much (e.g. more low or top end) like you can with a two stroke torque pipe/rev pipe. wanna know what the highest performance four stroke exhaust configuration is? go to the drag strip and look at what those guys use on 2500hp big block blown motors. nothing! 4" diameter open headers, about 10 inches long. but they'll make your ears ring at 100 yards.
Ya I've been hereing that yamaha's four strike is hard to start too. I'm not that expierienced with it yet but 1st or second kick and it goes. Most of the time (woods trails swamp whatever...) I'll have to get my wr up on its kick stand so I can really hop on the Kickstart, being extremely careful not to send it crashing into the foot peg. If it's cold, choke out, if it's hot use the hot start. Even if it's been down on it's side it will always start right up. It definitely took some practice. The manual recommends using using the decompression lever till you just get the piston past the comp. stroke. then kicking it. I found all that to be a waste of time. Just stand up on the thing and give it a nice swift kick ....it'll get easier once you find the right tecnique
eventually, starting without the compression release is going to cause your start shaft or idler pinion to break. by start shaft i'm not talking about the lever that you swing out to kick, i'm talking about the 0.5" dia shaft that disappears inside the engine.
i don't know about your compression, but i can just about stand my 180lbs on the kick start lever at TDC, it's not going anywhere. you're putting like 150 to 200 ft-lbs of torque (your weight X the length of the kickstart arm) on that 0.5" dia shaft pushing it through TDC like that. go get a half inch bolt and nut from the garage, mount it in a vise, and grab your largest torque wrench. see what 200 ft-lbs does to that half inch dia bolt.
if you don't believe me, wait 24 hours and at least 3 people will post that they snapped the start shaft and paid major bucks to get the internals fixed OR they were at the dealer and saw a wr/yz250f bike with this problem.
there was a post on DRN or thumpertalk fairly recently regarding a couple of breakages. as i recall one of the folks had a long arduous ride home with a broken shaft, after bump starting the bike.
i've seen a broken shaft from a 426. it was a BIG guy, and he was a newbie to this bike. you do the math...
now, there is a trick that one guy i know can do. he somehow pulls in the decomp lever, gives the bike a boot from whereever the piston is, then at just the right time on the downstroke he releases the decomp and the bike fires right up. for all observers, it looks like he's starting a 2-smoke. i never really figured it out.
hey wrooster,,, i usually have no problems with my YZF, but once in a while, if the bike is just idiling and dies out for some reason, it is an absolute bi#@% to start, I have changed plugs just in case ( 2 different occasions in the past) or get pulled to pull over............SO..... I am going to adjust the fuel screw, i will adjust in, as you recomend, upwards.... will it click or what, i always here " 1click in" for example, or should i just turn? and how much, just see how easier to start ? thanks for any input, you definately sound like you know what your talking about.... you are right on with the compression lever, thats why it is on there, use it...thanks for any imput.
It think the starting problems that were reported here and elsewhere were due to a couple of factors. First is the fact that the bikes are harder to start when new, before they are properly broken in. I don’t know why this is true but it sure seemed to be the case with my YZF. Secondly, the first bikes (YZ250F’s) were delivered in November/December. It has been my experience that all four strokes are a bear to start when it’s 10f degrees. Now that the weather is warm and my bike is broken in, I have found that I can start it first kick (most of the time) without lifting my butt off the seat, hot or cold! I have stalled my bike and had to make several kicks to get it going again but a cool head and a little patience would have prevented that. Use of the hot start button and the compression release (to clear it out) gets it going again in short order. You just have to remember to not start flailing away like you would on a two stroke following a stall.
My WR250 requires 2 twist of the throttle and the choke on to start in the
mornings and it starts on the first kick. After that any time I stop I hold in
compression release and kick through 6 times then do the drill and it starts on the first kick. If I set the idle screw up extremely high then it will start one kick without kicking through a few times with CR activated. I am reluctant to change anything as the bike runs perfect since the grey wire is gone. The one saving grace to this bike is you must make a horrendous mistake in order to kill the engine. At 5-8 I was worried the bike was too tall but I start it on the kickstand and when riding never notice the height, best to keep feet up anyway and who needs them down when the bike stays where you point it.
Since purchasing this bike I have become the energizer bunny as it is hard to get tired riding it.