NEW KX 250 preignition noise
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Junior Member
Joined: Jan 2007
Posts: 1
NEW KX 250 preignition noise
My KX250 is only a couple of weeks old and the first time I was able to open it up after breakin and there is a ping or knock in the top end at high RPMS in third, fourth and fifth gears. It sounds like an octane knock but I am running 93 octane mixed 32 to 1. Could the stock jet have me running too lean or would it be ignition timing. Looking for help, first questions to the dealer have not provided answers.
Junior Member
Joined: Mar 2007
Posts: 5
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RE: NEW KX 250 preignition noise
Its possible to be ignition timing...but i agree with 2smokers....whats the plug look like....if its too lean it will be lighter then tan to white......pinging is the fuel mixture detonating too early, much in same fashion as a diesel motor instead of using the spark plug....wont run quite right either......
Junior Member
Joined: Feb 2007
Posts: 15
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RE: NEW KX 250 preignition noise
It is absolutely important to use the right spark plug. the correct part is an NGK BR8ECMIX iridium plug. it is a short tower resistor plug that has a very high flame face.
If the incorrect plug is used the radio noise will cause the CDI box to malfunction. On your bike the CDI box controllsignition curve and also the powervalves. the noise you hear are the sub valves slapping open and closed under high engine load with the improper plug. While many plugs make the bike run, there is only one correct plug. The BR8ECMIX was designed along with and specifically for the '05 KX 250.
If the incorrect plug is used the radio noise will cause the CDI box to malfunction. On your bike the CDI box controllsignition curve and also the powervalves. the noise you hear are the sub valves slapping open and closed under high engine load with the improper plug. While many plugs make the bike run, there is only one correct plug. The BR8ECMIX was designed along with and specifically for the '05 KX 250.
Junior Member
Joined: Jul 2007
Posts: 5
From:
RE: NEW KX 250 preignition noise
You should run it on 95 oct. and never mix the 2 stroke oil in the tank allway´s in a gas bottle ( understand) 1-32? I did it allways 1-20 and never had problems!! and never let the 2 stroke bikes run in nutreal allways in high rpm... also what Mono said is correct....
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1st Gear Member
Joined: Feb 2008
Posts: 29
RE: NEW KX 250 preignition noise
ORIGINAL: Mono
It is absolutely important to use the right spark plug. the correct part is an NGK BR8ECMIX iridium plug. it is a short tower resistor plug that has a very high flame face.
If the incorrect plug is used the radio noise will cause the CDI box to malfunction. On your bike the CDI box controllsignition curve and also the powervalves. the noise you hear are the sub valves slapping open and closed under high engine load with the improper plug. While many plugs make the bike run, there is only one correct plug. The BR8ECMIX was designed along with and specifically for the '05 KX 250.
It is absolutely important to use the right spark plug. the correct part is an NGK BR8ECMIX iridium plug. it is a short tower resistor plug that has a very high flame face.
If the incorrect plug is used the radio noise will cause the CDI box to malfunction. On your bike the CDI box controllsignition curve and also the powervalves. the noise you hear are the sub valves slapping open and closed under high engine load with the improper plug. While many plugs make the bike run, there is only one correct plug. The BR8ECMIX was designed along with and specifically for the '05 KX 250.
Senior Member
1st Gear Member
Joined: Apr 2007
Posts: 2,317
From: Gibsonia PA
RE: NEW KX 250 preignition noise
A notorious problem. My friends new04 kx250 had the idenical problems. Tried everything, air screw, jetting, pipes, slider etc. Although he wasn't banging the power band as much as he should it was nothing but a headache. Just a bad carb design. Finally got tired of it and went to 4-stroke.
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