Honda atc250es being slow

[jvhill]

I just put on a 300ex carb and it seems to be slower than usual I tested the speed and only got up to 22 mph. All tires spin freely. Any help appreciated.

[coolpool]

Well first guess is jetting, starving it for fuel, but simple things first a) is your tank venting correctly, b) is your petcock flowing freely, c) how does the plug look after running it, lean (white) or rich (black), d) how did it run with the stock carb?

[350for350]

X 2 on the jetting. Swap the 250ES jets into the 300EX carb. Be sure to set the fuel screw at the 250ES specs instead of the 300EX. Not that I'm doubting you, but how did you come up with the 22MPH? Just curious. The 250ES should be able to double that speed plus a little more.

[jvhill]

The tank is venting and fuel flows from the petcock. I pulled the plug and it was black. The stock carb was junk ran really bad. I got the speed by using a GPS speed app on my phone. I'll try switching the jets tonight and see what that does.

[mooseknuckle]

The tank is venting and fuel flows from the petcock. I pulled the plug and it was black. The stock carb was junk ran really bad. I got the speed by using a GPS speed app on my phone. I'll try switching the jets tonight and see what that does.

How did the jetting work out?