Hawk RPS 250 - Throttle Issues

[neterno]

No performance parts on my new Hawk RPS 250.
No real miles (~25) on the bike.

Keihin clone carb.
NGK spark plug.
Idle mixture screw turned out 1.75 turns.
Valves set to .05mm
Air filter clean.
Idles good with K40 pilot jet. Throttle good up to about 1/4 turn.

Wide open throttle results in sudden power drop, chugging, some black smoke out of exhaust, and dies.
Between 1/4 and 3/4 throttle, loses power, no acceleration, but stays running.
These scenarios occur, without any difference, with all of the following main jets: K120, K125, K130, and K140. Needle is at notch 2.



Located outside Chicago - Roughly 800 feet above sea level.

[Megadan]

Main is too big. Drop to a 105, or at most a 110. Set needle back to 3rd slot.

[neterno]

I tried a K120 with the needle at notch 3.
And I tried a K125 with the needle at notch 3.
Still same results.

[Megadan]

Originally Posted by neterno

I tried a K120 with the needle at notch 3.
And I tried a K125 with the needle at notch 3.
Still same results.

So, you went from Too big to even bigger and it still ran rich? ...Think about what I said previously and apply it. Main jet is too big. Install a 105,, set needle to third notch.

[krat]

Got to agree, you need less fuel or more air. With no mods to intake or exhaust 95-105 should be right.

Mine came with an 88 stock and barely pulled itself down the road.

Mine will now run with a 120 but it has a cone filter and a punched exhaust and gutted cat. It still popped and backfired so badly I dropped back to a 110 and it smoothed out.