yz250

[BigH]

I know this is the kdx forum. First I want to thank everyone. My kdx200 is running amazing thanks to advise received on this forum. My son has a yz250 that has always ran perfect & started on 1st kick always. Now after it sits for a while (overnight) it wont start unless u use 1 small squirt of started spray into the airbox & then it will start all day afterwards w/1 kick? Checked compression, cleaned carb & jets, Checked ignition system (all measurements were good except primary & secondary coil readings) primary spec .2 to .3 ohms (reading .7) secondary 9.2k to 14.2k (measured 17.1k) but spark jump test good. spec atleast 6mm but would jump to 8 to 9mm. Tried jet needle at both position 1 & 2. The only thing I haven't checked was the stator area. Took cover off & no contamination or rust was evident & I don't have the special tool to take apart. but if I have a good spark I don't see how that would help. Also new gas was installed. I give up. What am I missing??? Thanks, Hal

[MarioM3]

Sounds like the air screw needs adjusting (could have turned out due to vibrations, or spring getting old). I would try that first. I also had a bike that was hard to start but once started it was fine, drove me mad. It turned out the filters on the fuel petcock in the tank were coved with debris, cleaned and readjusted air screw and solved it. Just throwing some ideas out, not sure if it will help. Good luck.

Mario

[BigH]

deffinetly not the air screw but the filters on the petcock is a possibility. I didn't even know there were filters in there. Still doubt it though due to after kicking it for a while gas does come out of the overflow hose plus it runs great after 1st start. not fuel starved. Will check it out though. Thanks

[gsa102]

Does it have an FCR carb? Try pumping the throttle 5-10 times if it does, then kick. It sounds like you are lean, but check the plug to see if it is wet with gas when it won't start. You may have to take the carb to a shop and have it soaked to really get the small passages clean.

What was your compression reading? Will it start if you pull it?

[6 Riders]

Before you start it, turn the gas on, lean the bike over until fuel starts coming out of the overflow. Then give it a kick. If that doesn't work, it is possible that it's time for a top end (piston and rings). When my KDX quit starting, I found the top end worn (including the electroplating in my case) and it wouldn't build enough compression to get it to start (easily).