Posts
255
Joined
3/26/2015
Location
Twentynine Palms, CA
US
Edited Date/Time
4/15/2023 6:09pm
03 yz125 used for desert racing (yes i know not the best idea). B level. Thought my jetting was pretty good. This piston and ring had 11 hours. seem to keep having a version of this issue. deteriorating head, cylinder, piston or all three like in this case.
To me it just looks like it got too hot. Thoughts?
No experience desert racing but all I can say is with my 125s, I've definitely sided a little on the rich side for main jets when riding sand/fast tracks. Stuff like Cahuilla or Pala main track out here in CA.
What fuel are you running?
What’s your jetting?
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pump fuel 32:1 maxima castor. using a lectron so i couldnt tell you the size of the jets.
I have no experience with that type of riding, but I’m sure you’re wide open a lot of the time so you’re going to need to be on the richer side. Kinda like 125cc shifter karts so they don’t melt pistons running wide open all the time. Way different jetting setup for that kinda thing.
Looks like serious detonation. After it’s all rebuilt, vacuum test engine, make sure no air leaks. Jet richer and work your way down to a safe leaner setting. Use better fuel, start with 50/50 C12 & pump. You are asking a lot of a high revving 125 in the desert on crappy pump fuel.
Yes, that is serious detonation caused by by way too lean for that type of riding. Which model Lectron are you using? Unfortunately, Lectrons are generally very lean which is why guys love them for tighter style off road riding. They don't load up, are always crisp, and get excellent mpg's. All of which is not what you want for wide open desert riding on a 125. If you have the H-series, it does have a power jet than you can open up to richen the larger throttle, higher rpm situations which would help this problem some. It is very sensitive.. so be careful. Might only take like 1/4 turn more open.
Major detonation! Sometimes you can hear and feel it, sometimes it's a silent killer.
Like everyone said, more octane and a regular carb with a bigger main jet!!!
ok really appreciate all the feedback. looks like lectron may not be doing me any favors. so ill switch back to the regular carb and a big fat main jet. also maybe some good fuel if i can find it.
Ran another top end with 100LL and a far richer needle and power jet (lectron). Everything seems pretty oily. How does this look? Should I go more?
How is it running? Does it feel OK? Excessive smoke or spooge?
Looks pretty safe to me.
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