KX250 spark plug go splunk.

Joined
Jun 18, 2000
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#1
Please help my buddy. He has a 1996 KX250 that he recently purchased used a few months back. I know the original owner and complete bike history. Anyone else out their with frequent spark plug filings? I run fresh gas with quality oil at 40:1. The bike runs strong, the only problem is after it sits for a couple days it always fouls the plug when starting. Change the plug and no problem.
 

dix

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Joined
Nov 24, 2001
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#2
Had the same problem with my 01 KX 250. Went to a hotter plug (BR7ES). No problems since!
 
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Sep 13, 2001
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#4
It is possible that the main crankshaft seal (on the clutch side) is worn and is leaking some oil into the lower end of the cylinder area. (kinda like a car engine will do when the valve guide are worn.) when you start the bike, the tranny fluid will foul the plug. check for pressure in the oil fill plug or declining oil levels.
I have a friend who has a 2000 KX250. fouls more plugs than i have ever seen. we are now trying a smaller main jet to see if this helps. his piston had quite a bit of carbon on the top, so it seems to be running rich. also, we found that when the bike was run really, really hard, it did not foul the plug on the next start up. (sounds like it is running rich....) I guess if you are racing and/or ride the dog poo out of the bike, it may not foul so much.

ps. we have tried different starting techniques and it seems to help sometimes. like, letting the bike idle some, remove choke, use small amounts of throttle until it warms some. but, still in all, it does eat plugs.....

third world racing team (get a new part, no way, give me the jb weld and some duct tape)
93 WR250, 86 YZ 250, 80 IT425, 75 Pursang 250 (ah, the bul)
 
Joined
Dec 24, 2001
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#5
raise your needle clip position.like if its in the third clip,put it in the secound from the top.