Very poor power in low gear

My blaster starts first kick every time and has lots of power in 4th and 5th gear and decent power in 3rd. But in 1st and 2nd it practically does nothing. It bottoms out at like 1/8th throttle in first gear.
I have a 1989 blaster with stock everything except V force reads 4, Oil injection block off, cheap air filter, brand new spark plug (Br8es),rebuild kit for carb which has stock jetting sizes. I’m not sure if I should get A bigger pilot jet and main jet because of the upgrades. But what I was thinking that was the cause is either it needs a top end rebuild. Because I don’t think it has gotten a rebuild yet. And if I stick a flashlight to the spark plug hole the top of the piston is pretty nasty, as far as black carbon buildup. BUT I do have good compression based on how hard it is to kick over. I know I should get a compression tester to see but I haven’t got my hands on one. Either that Or maybe it needs a bigger pilot jet.

But I didn’t want to buy a top end rebuild kit cause if it’s not the issue, It could waste money as they are pricey. And a mistake is easily made when installing them.

Anyways im not even close to an expert so I could be completely wrong about my predictions. That is why I am reaching out to you guys.

Thanks for responding

Oh yeah and there is a bit of a knocking noise in the engine too. So it would probably be bad piston rings… right lol. I did have a major air leak and was riding it for a couple days until I relised something was wrong. So
that could have also caused engine damage.

Larry's Shee said:

Try a better description of what it’s doing. It doesn’t make sense of your description of works fine in higher gears but not 1st or 2nd. Because it would pull easier in those gears. List all your carb jetting specs.

Get rid of that cheap air filter. Is the filter in the air box or directly on the carb?

Click to expand...

I rode it earlier and it just has power loss in general in every gear, it is just easier to tell when in low gear. My jetting is all stock but I have a 250 main jet sitting around.