[MotoNoob16]

Hey everyone, so I have a 2017 Crf125f. It’s my first bike. It was not idling without the choke and when I open throttle the bike would die out. I let it sit over the winter improperly, tried to clean the carburetor properly and it actually made it worse, so I ordered a new PZ26 carburetor. I installed it last night and the bike turned over and idled nicely without the choke. But soon after I had oil spilling out from the breather tube in the air filter box. I know the original size carb is 20mm and this one is 26mm. I read up that it fits a 125cc engine with no issues but this is where I’m stuck at. Any help would be appreciated!!

[Leardriver]

Modern gas doesn't like to sit for long in a carb. You didn't need a new carb, you needed to clean the old one, and the places where gas has gelled up and plugged passages isn't always obvious at first.
You are in uncharted ground with the new carb. Starting and running without the choke means that you are too rich on the pilot circuit.
Has the bike been on its side? Oil spilling out of the breather means that either there is way too much oil in the bike, or, more likely, the bike laid on its side, and has to ooze out all of that oil.

[MotoNoob16]

Modern gas doesn't like to sit for long in a carb. You didn't need a new carb, you needed to clean the old one, and the places where gas has gelled up and plugged passages isn't always obvious at first.
You are in uncharted ground with the new carb. Starting and running without the choke means that you are too rich on the pilot circuit.
Has the bike been on its side? Oil spilling out of the breather means that either there is way too much oil in the bike, or, more likely, the bike laid on its side, and has to ooze out all of that oil.

I originally cleaned it but I had the same problems. After inspection turns out my needle valve seat was damaged, so either way I was going to be required to change it out since The stock carb doesn’t sell seat replacements. I actually have not had the bike on it’s side almost at all since I’ve been trying to work on it. I did do an oil change before any of the carb problems started. Is there a good chance that it may have just had too much oil and the carb needs a tune? I was mostly worried about a blow by problem reading up that the pressure can cause that or if it was cause by going from a 20mm carb to a 26mm.

[Aussiecrf230]

If you overfill with oil generally the engine will push it out through the breathers with the accompanying mess. Occasionally the pressure might dispace a seal but only if breathers blocked.

The larger carb shouldn't induce blowby but may make it run poorly at low revs.

On the original carb was it the needle (part 13) https://partsfinder.onlinemicrofiche.co ... CARBURETOR

or the seat in the carb base that was damaged. In what way was it damaged?

The new carb may have to be the tuned to suit your motor or was it advertised as a direct replacement?

[MotoNoob16]

If you overfill with oil generally the engine will push it out through the breathers with the accompanying mess. Occasionally the pressure might dispace a seal but only if breathers blocked.

The larger carb shouldn't induce blowby but may make it run poorly at low revs.

On the original carb was it the needle (part 13) https://partsfinder.onlinemicrofiche.co ... CARBURETOR

or the seat in the carb base that was damaged. In what way was it damaged?

The new carb may have to be the tuned to suit your motor or was it advertised as a direct replacement?

It was the needle seat, I had the dealership inspect it and they don’t sell the seat separately like older carbs. I did buy a non OEM replacement for the cost and availability at that time. The brass on the seat had indents and scratches throughout inside so the needle was not closing properly. The new carb was designed for a 125-150cc engine.

[Aussiecrf230]

Do you know what needle and jetting is in the new carb?

Have you got fresh fuel in the tank and flushed line of old fuel?

Have you tried adjusting fuel screw to get an even idle?

You would most likely need to wash out and reoil the air filter if the airbox got flooded with oil.