Re: my 426 is kicking over without the compreshion...
I had the same problem on my 01 WR426 just recently after having it transported from Sydney to Perth. Valve clearances were within spec. I removed the head and poured a solvent down the intake and exhaust ports as detailed in the repair manual and found two valves on the intake side and one valve on the exhaust side leaking. After removing the valves I found small carbon deposits on the seats causing the leakage. I relapped them with the fine paste, reinstalled and found they held on both sides. At the same time I checked the rings in accordance with the repair manual and found them outside the standard spec but within tolerance and therefore replaced the rings as a set also (the piston and cylinder were still in spec and original hone marks were still evident on the bore). After replacing the head and the cylinder and installing the spark plug I kicked it over and had the compression back again (I can put my entire bodyweight on the starter and it will not budge at TDC). Hope this helps.
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did the guy give you the starting method. if not you have flooded the plug and it will only start if you replace the plug or dry it out. method. dont touch the throttle. pull decom lever and kick over 10 times. release lever get topwith kick start. pull decom lever slightly to allow kick start to drop 1 notch. release lever and let kick start back up and kick hard. repeat should start second go.
push the kick start through until you get to a hard spot(TDC) then hold the decompresser and kick it just a little more to get it past top dead centre. release the lever then one good kick, do not touch the throttle, even hold the bar not the grip so your not tempted to give it a squirt.
If it also has the hot start lever, or button this is for when the bike is quite hot and it leans out the mixture for starting, activate the lever and start the bike, then release the lever. This also helps if youve had a little lie down and the bike is flooded
what also helps starting is new spark plug clean air filter new oil check valve clearances a small squirt of upper cylnder lube in the tank
Standard starting procedure for YZ400/426/450 is as follows: Push the engine around using the kick starter until you hit the compression stroke. The kick starter will get impossibly hard to push at this point. Now pull in the decomp lever and push the kick starter down a fraction, and I mean a FRACTION. This is where most people go wrong, they push it down too far with the decomp lever pulled in. Now give it a full kick without throttle and it should start.
The above should work fine for a motor that's already warm and was NOT stalled. If the motor stalls it will usually need the hot start button opened as well to let extra air in and bleed out the fuel that usually gets stuck in the motor when it stalls.
For cold starts, you will need to put the choke on, and if it's really cold you might need to prime the engine with a twist of throttle to get the accelerator pump to shoot some fuel in before you start.
As a general rule, NEVER twist the throttle while kicking when you are actually attempting to start the bike, it won't help at all. Also, having your idle screw adjusted correctly makes all of this a lot more easier. Standard setting is usually 1.5 turns out but it should be set to give the smoothest idle you can get using the minimum number of turns out from all the way in. If you have to wind your screw right out to get a good idle you need a bigger pilot jet. Conversely if you have to wind it most of the way in (less than 1 turn) you need a smaller pilot jet. I'm not sure about the 450 but my YZ426 came standard with a 42 pilot jet and changing to a 45 made it idle and start MUCH better. Incidentally the WR model uses a 48.
Is it a kick start or does it have a kick starter in addition to the electric start? If so then it is a decompression lever which you pull in when you are trying to start the bike by kick start. Hold in the lever and try the kickstart vs not holding the lever. You'll feel a huge difference.
For a cold start, turn fuel on at fuel tap. Pull out the choke knob. slowly kick the kickstarter until you feel it become harder(more resistance). push past this resistance then release the kickstarter. What you have done is put the piston in the position just after top dead centre of the compression stroke.Now give it a big kick whilst opening the throttle slightly. There is a real techneque to it so don't think your the only one who has problems! Otherwise, ask your local Yammy dealer for a look at the owners manual. It has a description on how to both hot & cold start your bike. They may let you photocopy it. Good luck.
If it just isn't happening try removing the sparkplug,put it back in the plug cap,rest the plugs metal body on the cylinder head (don't hold it there or you could get a nasty shock) Now kick the kickstarter while watching the sparkplug gap. Did it spark? If it didn't theres a problem. No spark means it wont run! Then you'll need to find out why theres no spark. Hope this helps to get you started Otherwise let us know and i'll se what else I can suggest.
The starting procedure is... Kick it over slowely untill it stops, pull in the compression release lever and kick just a little more to get it past "Top dead center". (An inch or two) Then let the kick starter return all the way up, .... and give it a smooth firm kick. Not a ****.