Hey UTV Board stie Admins: The board  needs to award Ben1098  the UTV Board "Medal of Honor".  !! 👍👍👍  

Just a thought here...how is compression?  Too tight exhaust can burn a seat and leave you with poor compression. 

Yeah, I was going to fab something until I realized that the valve cover on my motor barely comes off due to the shift cable plate on the gearbox. I have no room left. Even if I did, the belt would have to be custom.

I have a 2021 Massimo MXU 1000.  Last winter the front drive shaft sheared off inside the motor and it was cheaper to buy a new motor than to take it apart in order to remove the front drive shaft that was broken inside the case… Now it is running rich, seems to maybe be geared too high, does not accelerate well once you hit about 28mph.  I’ve replaced the O2 sensor.  MAF is next (I accidentally ordered the wrong one, but when I removed the old one you can clearly smell fuel).    I’m not a motorhead but I can turn a wrench.  Any ideas how to get this motor optimized?  The motor has about 300 miles on it.  I broke it in as recommended in the manual. 

Only thing I can think of that you haven't already done is look at the fuel pump. There is a filter on it but you have to pull the pump to look at it. If that is the problem consider installing an inline filter before the pump.