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Discussion Starter · #1 · (Edited)
Hey everyone, I am new here and have been searching for carb tuning tips for months now and can't get it right. It's always a different setup for everyone so I'm starting my own thread to hopefully figure this out finally.

I have a Sportrax 300ex with HMF slip on, and quiet core installed. Trying to get the jetting correct.

Backstory: i had the jetting close but with poping on decel but was rideable. 14 miles into a ride it just started stumbling and losing power and cutting out above 1/4 throttle. I have a gopro video od the moment it happened, was riding on a hard road and then just total crap performance. Worried that i have a bigger issue.

After several times taking carb off my current status is this.. running great on idle, no more popping, ok putting thru parking lot to trail, then as i hit first trail and get close to half throttle, stumbling cutting out,loss of power,jerky. Also have gas coming out overflow tube when this happens but not at idle.

HMF slip on with quiet core
Slow jet: 42 (stock was 38)
Fuel screw: 2 1/4 turns
Main jet: 126 (stock was 123)
Needle: lowered one notch to richen
Carb is clean,used a rebuild kit as well
Airbox has holes drilled, might run slightly better with holes covered but hard to tell.

I feel like air is coming back out the airbox when i cut the throttle from 1/2 to none.

Increasing the slow jet from 38 to 42 did get me from the problem happening at 1/4 up to half throttle. Seems to run ok at wot. Should i increase another step?

Last 3 trips to the trail i haven't made it more than 50 yards without leaving! So i need to fix this. Thanks for any tips!
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