Brand new 2013, problem with startup only (fouling plugs)

ive looked everywhere for this same problem and cant quite seem to find someone thats had the same thing so here it goes!

 

My bike is a brand new yz 250, 2013. since ive bought it ive had this same exact problem. 

 

When i start up, the bike idles and runs fine. everything seems to work fine. let it warm up, jump on the bike, and go about 100m and the bike will foul a plug. I change this plug out and the bike will run perfect the whole day. then if i let it cool off a bit, and fire it back up it will foul another plug. its always been like this.

 

When i go to start i will try to open it up and it will start to sound boggy and then that plug needs to be changed out. 

 

Plug when taken out is black in color.

 

Anyone know if this is the jets or a dirty carb or anything like that, the bike runs perfect except this initial start. everything in the bike is new and stock, and the air filter is clean. running 40:1 for mixture on fuel.

 

any replies would be awesome! thanks

well first question will be what exactly is your warm up routine? followed by what's your current jetting and elevation?

Stock jetting is quite rich on the pilot circuit.

Warm up just standard 2 stroke warm up. Idle and small blips on the throttle. Current jetting is stock 2013 yz 250. Elevation is 1200ft

Standard 2-stroke warmup should take less than a minute.  How long are you idling it on the stand?

"Blips" of the throttle might be causing some issues too, during warm up. A nice, steady, slightly higher than normal idle is easier on the engine & plugs than "blipping" the throttle during warm up.

What oil are you running? I was running castor 927 for a while and if the bike wasn't ridden hard, it would foul the plug just like you describe. I changed oils and it made the difference. On a side note, I was mixing rich just for security because I used to wring that 125's neck

oil is yamalube 2-R 2 stroke oil. Apart from that initial startup the bike works and runs fine always regardless of what im doing. it's just fouling a plug each and everytime on the startup. I was wondering if it was my Pilot jet, i've tried a multitude of things and the only thing i haven't really tried is changing Main jet , pilot jet,  needle / settings for each of these. Would adjusting the air screw make a difference? Change the idle adjuster in or out? any thoughts? you should definitely get more than a "ride" on one plug.

where in alberta are you?

Northern. Mcmurray

ive looked everywhere for this same problem and cant quite seem to find someone thats had the same thing so here it goes!

 

My bike is a brand new yz 250, 2013. since ive bought it ive had this same exact problem. 

 

When i start up, the bike idles and runs fine. everything seems to work fine. let it warm up, jump on the bike, and go about 100m and the bike will foul a plug. I change this plug out and the bike will run perfect the whole day. then if i let it cool off a bit, and fire it back up it will foul another plug. its always been like this.

 

When i go to start i will try to open it up and it will start to sound boggy and then that plug needs to be changed out. 

 

Plug when taken out is black in color.

 

Anyone know if this is the jets or a dirty carb or anything like that, the bike runs perfect except this initial start. everything in the bike is new and stock, and the air filter is clean. running 40:1 for mixture on fuel.

 

any replies would be awesome! thanks

After the bike is started put the choke back in right away and let the bike idle by slowly opening the throttle .Don't let the bike idle with the choke on for more than 1  min as it will not warm up the bike properly because there is too much fuel  and then you twist the throttle hard will foul the plugs .

You don't think its jetting at all? Just start up ?

You don't think its jetting at all? Just start up ?

How long do you leave the choke on for? Personally, I turn mine off immediately upon start-up. Sometimes I have to ever so slightly open it up again every few seconds until the engine has enough warmth to run on it's own without the choke, but I use it incredibly sparingly. As dirttracker said, the choke adds wwwaaaayyyyy to much fuel, and will easily foul a plug.

I do the same i don't leave it on for long at all. Don't understand why the bike is doing this i bought it brand new off the lot. So strange.

You don't think its jetting at all? Just start up ?

 

You don't think its jetting at all? Just start up ?

You might need to drop the pilot to 48 or open the fuel screw 1/4 turns more but I think the biggest problem is how you start the bike. Are you using 8 plugs and how cold is the ambient temp ?

Try this even if it sounds too simple. I ride hard in the woods, tight woods. It runs great all the time. It builds up spoog, unburned oil? for lack of over rev. I would park the bike, all the oil would settle into the base and wait there. Next time out bike would start fine, when I would go to start riding and clear its throat the oil would blow out of the base and put the fire out! Now when I'm finished riding I go out into the open and clear its throat (over rev) until no more blue smoke clouds (three good long rips usually does it). Then shut it down for the day soon after. Ever since I started blowing out the excess at the end of the day I have not changed the plug (2 years). Now I just start it up, warm it up a little, take off and clear its throat with a couple of quick rips and its good for the day. When I'm done I blow it out good and put it away. Hope this helps.....Kinger

if was my bike i would check my float height was correct just because it's not puking out fuel from the over flow tubes doesn't mean it could be off slightly from the factory it has been known to happen. my 06 has never done that doesn't matter if i trail or mx the owners manual says to use the choke for 30 seconds then turn off.

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