need help -bike running way too rich

thirtyfour

Member
Oct 27, 2003
34
0
guys I need some advice,
history of the bike
the bike is a 2001 KX 250
I got it used with very little use on it.
40:1 gas/oil mix, premium pump gas, yamalube R2
sparkplug NGK BR8EG , BR8ES
the bike runs very rich, and dies after some run time. or won't restart after letting it cool down.
the plug it is black but not WET, the reason it dies the spark jumps at the base of the spark plug instead at the electrode.
If I put a new /clean plug it will run just fine for a while.
things I done so far;
repacked, cleaned bafle on the silencer, checked carb jetting stock main is 160 , the bike has a 155 , stock pilot is 52, the bike has a 48 in it.
checked the float level= ok, clean air filter with little or no oil on it.
checked the reed valves , not chiped or dameged.
adjusted the air screw 2 turn out.
the bike runs strong and starts every time on first or second kick(except when the plug gets fouled )
what else there is to check to see why this bike runs so rich?
Cranks seal? , how would you check it wihtout disassemble?
 
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kshackleton

Member
Oct 12, 2005
109
0
If the bike is running fine with a new plug.....perhaps it's not rich at all. Rich mixture would run crappy as soon as the engine heats up even before the plug fouls. How long does it run well? Perhaps there is another problem that is fouling the plug. You did not mention needle height, and the air screw spec is 1.5 turns...not 2 turns out [but turning it out leans the pilot mixture].

Perhaps the needle/seat in the fuel bowl is leaking....and dumping extra fuel into the engine even though the float is at the correct level. Have you examined/changed the needle/seat?

Removing the flywheel cover [left side] would allow you to see if the crank seal is leaking on that side. If it is leaking, I would imagine that there would be a lot of contamination there. If it is leaking on the other side, then I would expect that the tranny oil would get a certain amount of fuel contamination.
 

psalm3124

Member
Apr 21, 2005
101
0
Sometimes the oil seal on the right side (if you're sitting on the bike) of the engine will leak. check you tranny oil level to see if you've lost much. I had a 94 KX 250 and it was notorious for that problem. But then again, I just had to replace the oil seal in my 02 YZ also. In both cases I had the same symptoms as you are describing. Good luck.
 

thirtyfour

Member
Oct 27, 2003
34
0
thanks guys,
the carb needle is in the 2nd clip
float /fuel needle looks good so does the seat.
the reason the air screw is out 2 turns because I was trying to help the situation by leaning out the mixture on the first part of the throtle opening.(idle- 1/4 )
You are right it is possible that the jeting is right on the money, and other thing makes it puke out, and this is my fear, the right side crank seal allowing trans oil in the crank case/messing up the plug.
like i said the bike has lots of power , starts easy, idles fine pull strong, but something kills the spark/spark plug.
any way to test the condition of the right side crank seal?
if it is bad how big of a job to replace it?
thanks again.
 

kshackleton

Member
Oct 12, 2005
109
0
Hmm....I was thinking about the pressure pulse sending fuel into the tranny, not the partial vacuum drawing oil into the crankcase....that could certainly foul the plug.

If that was happening, you should notice lots and lots of smoke....my KX does not smoke too much once warmed up [Bel-Ray synth at 40:1].

I have never changed that seal, but according to the shop manual....it would appear that the case needs to be split to get at that seal.....looks like a major undertaking. You will want to make sure that's the problem first....does the tranny oil level drop?
 

thirtyfour

Member
Oct 27, 2003
34
0
no I have not noticed the oil level drop,
however I can't really ride the bike too much in this condition,
I would think the piston upstorke wacuum would pull some trans oil in which would mis with the premix not sure how the trans oil would burn during combustion.
different question? where did you get the shop manual?
I looked on Clymer , they only have it up to year 2000 for the KX
thanks
 

kshackleton

Member
Oct 12, 2005
109
0
thirtyfour said:
no I have not noticed the oil level drop,
however I can't really ride the bike too much in this condition,
I would think the piston upstorke wacuum would pull some trans oil in which would mis with the premix not sure how the trans oil would burn during combustion.
different question? where did you get the shop manual?
I looked on Clymer , they only have it up to year 2000 for the KX
thanks

Shop manual from the dealer....kinda pricey at $60...but it does have a lot of good info
 

thirtyfour

Member
Oct 27, 2003
34
0
at this point I am trying to rule out all the other possibilities before diging into the case for a crank seal,
anybody has any other idea, what else to check?
changing trans fluid to a different kind which would clearly indicate a leaking crank seal?

thanks
 

AssistSuper

Member
Apr 4, 2005
287
0
I'm with Masterphil,

I would mess with the jetting before going to all that trouble.

If your jetting is too rich, it doesn't necessarily mean your bike instantly fouls plugs.
 

thirtyfour

Member
Oct 27, 2003
34
0
thanks , I would love to read it , but when I click on your link I get a message :
Sorry - no matches. Please try some different terms.
I even copied the whole link to a new browser and got the same message.
is it possible that I am not allowed to do such search,
any other way you can point me to that thread?
I am able to search by user name or by words in the post .
can you tell me who posted the messageand on which date?

thanks
 
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