'13 250sx spewed coolant under light load, weird!

Ok, this really confused me yesterday so I'm wondering if this has happened to anyone else.

 

Background:

2013 250sx, jetting is great and runs mint. Almost 17 hours on the bike and never any problems at all (all mx riding).

 

Issue:

Yesterday, I go out on track with buddies wife and tow her around to show her lines and whatnot. This is literally the only time I've gone out and putted around without really going wide open at all. I just went around for 3 laps and pulled off. At this point my motor was smoking and I noticed coolant sprayed all over the front. It seemed like it spewed coolant from the overflow line (where it connects to the frame in front).  

 

I let it cool down and replaced the bit of coolant that leaked out and then rode a few sessions how I normally do, riding it hard. It was fine and never lost anymore coolant.  WTF!?

Actually doesn't sound all that abnormal. Figure you have the weight of two people on the bike and you are not moving hardly any air over the rads. If your jetting is right on the cusp of being lean (which is optimal in a 2t) then I can see it spewing some coolant. You may want to richen it up just a little bit.

 

 I go out on track with buddies wife and tow her around to show her lines and whatnot.

 When you say towed her around, you mean what, her and you on your bike?

Actually doesn't sound all that abnormal. Figure you have the weight of two people on the bike and you are not moving hardly any air over the rads. If your jetting is right on the cusp of being lean (which is optimal in a 2t) then I can see it spewing some coolant. You may want to richen it up just a little bit.

Ah sorry I wasn't clear, she was on her own bike. I was riding single, just riding in front of her :)

 

Jetting was fattened up and is definitely pretty on point. In fact, stock main jet was like a 160 and I'm running a 172. Maybe down low I am a bit lean though, thanks for the reply.

Yeah, maybe step up the pilot one size.

Right on, I think I'm the stock 40 pilot and might try 42. Thanks guys

They over heat idling to long don't stress I freaked to I have maybe 3-4 hours on mine if you run it rich it will run hot period.

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