2018 XC 250 pilot
 

Anyone know what the stock pilot size for 19 XC 250? Have a #40 in there and its tough to kick over, but starts fine with the starter. Has new JD kit in it. Main is 170, needle in middle.

How does it idle, and how is off idle response? You may need a 42 pilot depending on temp, elevation etc.

Hard to start on the kicker first start of the day, or consistently after the bike is warm?

Try adjusting the air screw all the way in and then say 4 turns out. If it starts better fully closed you probably need a bigger pilot. If it starts better with it four turns out you would need a leaner pilot, but I think that is unlikely.

Just 1st start of the day. Once warmed up its a couple kicks. I'll try the air screw and see what happens. I have a 45 pilot sitting around. Might throw that in and see what happens too.

on the earlier bikes it was a 40 pilot, i think at high elevation i went to 38.

The check is based on air screw. from google:
 Start with a fully warmed up engine at normal operating temperature.
 High performance 2 stroke engines are very inefficient at low RPM and therefore it is usually best
not to set them to idle. You will find that the idle speed adjustment and the required low speed
mixture setting will change drastically from a warmed up engine in the pits to a hot engine
several laps into the race. It is best to set the slide position (idle speed screw) so that the engine
will return to a low RPM for a few seconds and then die. In actual use while riding this has
proven to work acceptably.
 Initially adjust the low speed mixture screw to approx 3 turns out from all the way in. On two
stroke carburetors this is an air screw so don’t forget turning the screw out is a leaner mixture.
 Using the throttle, keep the engine at a low RPM, just above stall RPM. Use the throttle to slightly
increase and decrease the RPM. Turn the air screw in ? turn at a time until the engine sounds
heavy and rich like the choke is on and the throttle response is slow (don’t forget that you are
only twisting the throttle slightly). Then go back out with the air screw until the engine sound just
cleans up. (it should still sound very slightly rich but it should respond and clean out instantly
when the throttle is opened ? to ? open)
 Your final setting on the low speed mixture screw should be between 1/2 and 3 turns out from
completely in. If you are less than 1/2 turn, you need 2 sizes larger pilot jet. If you are more than
3 turns, you need a pilot which is 2 sizes smaller

I really disagree with the old 1970's ideology that a 2T shouldn't idle as it's just not true. I agree they are more inefficient at idle but that's the case over the entire rpm range except for what rpm the pipe is specifically tuned to. Every 2T I have ever owned (KDX's, KX's, YZ's, EC/DE's, IT, and RM) would/will run and idle really well all day on my initial air screw adjustment as long as I'm riding similar elevation for the day.

I follow a different jetting guide that has worked perfectly to really dial in the jetting of all the bikes I've owned or presently own. Here is the procedure for the idle (pilot jet) circuit and how to determine if you have the correct pilot jet...

What is often missed when switching needles is to reset the idle screw.

also, you might end up at up to 2.5 turns out on the airscrew and everything will be fine...

The idle screw needs to be backed out to bring the slide and needle down to better separate the idle and mid circuits in the carb.

One way you can tell if your jetting is still "non-optimal" is if your air screw (idle mixture screwi) still has little effect.

In my opinion, if have a "good needle" and you are down to a 38 pilot and looking for something leaner - then your idle might still be cranked up too far.

My experience is that - set up properly - with better needle installed, jets & idle and air screw settings good - it will start easily and idle too... (BTW - a yamaha yz kickstarter helps too).

jeff

Above is all great.

But I will add, pilots like to block, bad starting will be a symptom. Any running issue clean it out first. 2nd, run the bike through the gears. Trying to tune anything before the metal is operating temperature is a waste of time, plus the old gas in the bowl will have ,gone off quicker than the rest in the tank.

Then start.

more info.
 

This is on a 2019 XC 250, I bought the bike last Sept. 1st ride was a cool morning and tough to start, about 10+ kicks. When running all seemed fine, but only rode for 45 mins. Next ride was about 2 weeks later and much warmer, about 8 kicks or so, run good but was muddy and slick. Havent riiden since due to back issues. Putting the bike up for sale. Got the JD rebuild kit. A 38 pilot was in there and 180 Main, think stock needle. Put the JD kit with 40 pilot, 178 main and whatever the blue needle is on center. Tried to kick it over and got to about 6 kicks, had enough, used the starter and started right up, didnt ride it. Fresh gas too.

If you are using the choke then you should not have that issue.
I'd bet you $5 you have blocked pilot (payable only in person).

Check/change plug.