Atc250es keeps fowling plugs.. Looks like oil??

[Big OL Red]

I was riding today the bike just shut off, I pulled the plug it was fouled bought a new plug put it in the road and around my house twice parked it tried to start it back up Would not start, the plug was filed again black and wet

[dustrunner]

welcome, does it smoke when running ? did you just get it ?

[tri again]

I think you would've mentioned if it purred or sounded like the choke was on?

Just a thought fast and free:
'unscrew' the sparkplug cap and nip the last tiny bit off the coil wire
so the cap can screw into some fresh copper.

It's messed me up more than a few times after checking everything else...timing, valve adjust etc etc.

Good luck and please keep us posted.

We all need to know this answer.

ps - airbox clear?
Air through frame clear of mouse / bees nests?

[Big OL Red]

The bike smokes when I first start it for a few min. Then it stops after it warmed up. I just got it a month ago only ran about a tank of fuel threw it. Ran decent except for a Top end tick that I am not sure what it is I think it's the timing chain it is not the valves tho. I dropped it off at the shop today I should find out the damage in a few days.

[dustrunner]

welp, im thinking valve seals , but please let us know what the shop says.....

[kb0nly]

Probably valve seals, timing chain, and also running a bit rich.

[rcurtis16]

cant be valve seals, if it was she would smoke like a chimney, valve stem might be wore, and the ticking is from bad valve gap, probly worn cam, the fouling of the plug is probly to weak, or to strong of power going to the coil

[kb0nly]

Uh yeah it can, very very common...

If it smokes when first started but goes away quickly its almost always 99.9% the valve stem seals. The oil leaks down when its cold, then you fire it up and she burns off that oil that leaked in and the seals get warmed up and they seal back up. Its the reason i pulled the head off mine and three others this past year, its a very common problem on the 200 and 250 motors. If it was smoking like a chimney then its rings... Valve stem seals will never cause her to smoke that bad because of the way the oil flows up in the head, it needs time to seep down around the seals and it cant while running. I have seen 200's with totally shot valve stem seals that will not smoke when running, but shut them off for ten minutes and fire back up and it smokes for 5-10 seconds and clears up again.

Ticking is usually valve lash or loose timing chain, which causes a lot of noise and vibration in the top end.

Fouling "could" be weak spark, i say could be because most of the time its not. Generally its due to the carb being set too rich, or problems from sitting, etc. I don't see how too strong of power going to the coil could be causing a fouled plug, if anything that would fix the problem causing a hotter burning plug.

[dustrunner]

i totally agree with kbonly... your spot on.....

[rcurtis16]

LOL, i bought a big red, she worked good, i changed the oil, she smoked like a chimney, when i pulled the top end apart, my valve stem rubbers were toast, i knew it wasnt rings bc i could still take her a wheelie the whole road, yeah i wasnt a 100% on what plug fouling is, i found out after, we say it different here, i pulled my motor the rings were fine, there was basically nothing left to my valve stem seals, i burn a litre of oil from my house to the gas station and back lol

[yaegerb]

Its your valve seals. Telltale sign is the bike smokes on start-up and then goes away when the engine is warm. Its because the seals will expand when the engine is hot and when it is cold they contract beyond normal specifications. Yours are worn and its a fairly easy fix.