Need help reading plugs that i keep fouling.

sinner 04

Member
Sep 12, 2005
27
0
I have 2004 CR125R that i bought brand new last week (old stock).
I'm new to 2 stroke motors but i'm a car guy so i have experience that should transfer over and i'm not afraid to get into the motor.

I'v been fouling my plugs after about 10 mins hard riding. Usually after i come to a stop and start moving again (no signs it was gonna foul).
I'm using Honda HP2 oil mixed at 32:1. Stock pipe. I don't give it any throttle on start up and turn the choke off right away. I'm at 2,200ft elevation and the temp is ranging from 8-15 C* or 46-59 F*.

I went to a Honda shop and talked to the Mechanic and he said to try re-jetting the main jet, so i did a 400 from the stock 420. I took it for a rip and same thing after almost 10 mins. This time i was riding and i could feel it losing power so i drove it easy around the corner back to the truck and stopped, where it idle'd for a little before it died.

On the first start up of the day the bike smokes a lot when i give it any kind of throttle and sounds like i have the choke on, after about 10mins idling it clears up.
Riding it...at about idle to 3/4 throttle just before power band it feels pretty crappy until it's really warmed up. (before and after i re-jetted it)

If it's hard to see the plugs they are half soaked in oil but the parts that aren't soaked look tanned, like it should. So what does the plug mean? And where should i go from here? leaner, new jet needle, different jet needle setting, slow jet? Any advice to help keeping the plugs alive?
Thanks IA.

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DR4Ztrokes

Member
Aug 16, 2001
19
0
Dealers typically use different pre-mix ratio for the first tank for initial break-in period. If you have not run a full tank of gas through it yet there may be too much oil in the mix to burn clean especially if you are not revving it way out. Might tray draining the tank and using pre-mix at the correct ratio.
 

Rich Rohrich

Moderator / BioHazard
LIFETIME SPONSOR
Jul 27, 1999
22,838
16,902
Chicago
sinner 04 said:
Need help reading plugs that i keep fouling.

There is nothing to read on a fouled plug, other than the fact that it is fouled.

The pilot jet is usually way too rich at seal level, at 2200ft it only gets worse. Start with the basic stuff. Fresh fuel, lean out the pilot jet, run a BR8ES instead of a BR9ES and don't let it idle. Two-stroke 125s MX bikes are not designed to idle.

If you feel ambitious you can pull the carb and check the float level. It's set too high on a lot of bikes.
 
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