i have read a few things about trying to get a increase in performance out of the 20hp honda gx620,i seen that i could add the hi rev springs for the valves,gut the exhaust, adjust the carb from running too lean. MY question is, what would yall recommend? Bottom line is i want to get a little more top end out of it. Im not sure what adjustments are needed to "un lean" the carb, and exactly what parts i would need for the valve work. I am currently running a 15x40 crawfish skiff, planning on building a new one around 18x38. Just curious if any of you have any ideas or tips to point me in the right direction

I have a gx670, not sure if this will work for yours, but here is what I did. Robertson torque tubes vtwin exhaust kit and welded it up to a y collector and into a tractor style 2" muffler. Main jet went from 98 to 105 and when the carb was off I used a pen torch to remove the epa limiters on the idle mixture screws so that I could remove the lean bog off idle.

On my heavy 18x50 custom I went from 16 mph(occasionally bump 17 when things were perfect) to a solid 20. Bottom end torque was much better than stock.

Good luck bud.

That's pretty significant in my book lol, I will wait until after hunting season and see what I can get out of it

Send me a pm when you get ready to do it and I will text you pictures of my exhaust and answer any questions I can. Good luck!