So just picked up a 300st 2015 bike was running went out all day had few issues with it stalling on hill descents , it didn’t start super easy 3 or more kicks , so go it home washed it started it ... put it away for 4 days got new plug drained fuel tank added fresh petrol ... trying to treat her nice 

now bike is just dead not even a chance of firing nothing 

I have a solid spark , I have fuel in the carb Lean the bike and fuel comes out the overflow , plug is wet on kicking the bike over .. 

 

unplugged plugs and connections , disconnected the kill switch no change 

 

really stumped any help appreciated , other are pointing to crank seal just can’t believe that had solid day on it 4 days ago ??‍♂️
 

thank John 

Try old plug again.

Or fuel tap off, plug out, kick several times as maybe build up of fuel in crank case. 

Try kicking plug in, fuel off, no choke.

Pretty much tried all that mate been on it two days now 

Timing

Guy

Stalling on descents & wet plug would suggest too high a float height. Try starting it with the fuel off with a dry plug & no choke

Stuck float? Clogged jet? If it wold me, I will clean carb, and check reed valve

Check the throttle cable hasn’t been pulled up slightly, if the outer cable isn’t sitting in the metal flute fully where it enters the carb you’ll not get it to start. 100% Don’t attempt to bump start the bike! It’s not staring because there’s a problem, I’ve seen 2 of these exact bikes destroy a piston and barrel from being forced to start while the cable isn’t seated fully. 

I have cleaned carb out several times not touched reed block yet , will check the throttle cable and see 

 You did not lose the little needle jet holder when you cleaned the carb? You might send a picture of around the slide area. We have seen that happen before. Only on the forums. LOL.

The sherco's with the rear tank/pump are known for stalling when going downhill. Turn the idle up a little and give it a rev now and again when you hear it starting to bog. 

The non starting sounds like excess fuel/ flooded. Providing you have rebuilt the carb correctly, turn the fuel off, plug out and give it a good few kicks over, put clean plug back in and kick it with throttle fully open  it might take a few kicks and will sound bogged up until it burns the excess fuel out then it will return to normal and you can put fuel back on. 

My 2014 sherco would flood getting it off the back of a pick up truck all the time. Wide open throttle and kick would be the only way I could get it to start after that.

Edited December 13, 20196 yr by Spanky
Spelling correction

Flywheel key         Stator

Edited December 13, 20196 yr by midlife

I believe that guy53 is correct and that the woodruff/flywheel key may be compromised. Pull off the flywheel and check.

So finally got it going , still not sure what’s wrong but ... changed crank seal and nothing , so started stripping it , took exhaust off and it was full of fuel , as the bike is new to me i May have left fuel on. , some how it’s flooded the bike , some things wrong but at least it runs now ... going to buy few new parts for the carb , 

 

at one point this week I had fuel coming out the overflow pipe so had carb apart about 3 times 

On the rear tankers, the fuel pipe goes up to the top of the tank, then back down again,  The pipe goes hard and splits.  This can result in all sorts of strange things happening.  In the 3 years that I had my 2014 I replaced the entire plastic fuel pipe at least twice.

I also had an "overflowing carb" which turned out to be coming from a split in the fuel line NEAR the carb.

Leaving fuel on shouldn't cause any problems if the carb is set up/ working correctly. You say you've had the carb apart, I would strip it again to confirm the float height is correct and its shutting off the fuel when the bowl is full. You dont say whether you've had the bike on its side while working on it but if you have with the fuel on it's a sure fire way to fill the crank with fuel (I did it on mine once servicing the dog bones when i forgot to shut the fuel off). Splatshop has some good information on setting up the carb (the keinhin is a temperamental beast).