Why does my wheeler die in high gear? - Kymco 2010 MXU 375 IRS 4x4

Question edited for clarity.
Question moved to ATVs.

There are no clues in the link or in the service manual except that the transmission is failing.

https://www.google.com/search?q=yukon+cxl+150+dies+in+reverse+gear

https://get2itparts.com/etontech/SM_150cc.pdf

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If by last gear you mean the high gear, then you are likely hitting the rev limiter or speed limiter.

The float is stucking in carb. While its running try tipping on the carb. Bowl. It may free it loose.

You can try to adjust the linkage below the shifter should be 2 rods there one is low gear other is forward and backwards if that's doesn't do it then you have to pull trans out and sleeve the shift heads hope you can just adjust it

If you need further help, I’m available over the phone at https://www.6ya.com/expert/brandon_79b580f5a99c4386

you need to replace high gears !!

Try changing your fuel filter

If you need further help, I’m available over the phone at https://www.6ya.com/expert/brandon_79b580f5a99c4386

try backing out your fuel/air mixture screw 1/2 a turn. This should be 3 turns out from seat.

I'm pretty sure there's no vacuum lines on it. clean your carb

it needs a set of rings and maybe a piston then it will be like new again

my artic cat did this found that the carb was dirty