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I have a 2005 CRF150F that very low hours. It's mostly stock except the previous owner installed a BBR exhaust and a K&N air filter. I got it with old gas and I cleaned it well. It started great but wouldn't idle. So I cleaned it again. Same thing. So i replaced the pilot jet. Same thing. So I disassembled the carb completely and soaked it in the Berrymans carb cleaner bucket and carefully reassembled. Exact same problem. The bike is for my daughter. She's not going to enjoy a bike that stalls constantly. Here's the carb specs. Keep in mind the exhaust and air filter and I'm sea level.

Keihin PD
110 main jet
40 pilot jet
H5d slide
30k needle
Clip in 3rd (middle) position
Fuel mixture screw 1.5 turns out

I'm out of tricks. I don't know what else to try without just guessing. I'd appreciate any help if you've experienced this.

Thanks

Chris

So I've moved up to a 42 pilot jet and now it will almost idle at 4.5 turns out on the mixture screw. Going to pick up a 45 pilot jet and try again tomorrow.

Anything past 2.5 turns out indicates you need to move up to a larger pilot jet...which it sounds like you are doing.

Ken

OK so to get caught up, I tried incremental pilot jets up to 50 and it still wouldn't idle so I suspected compression. Since the machine has barely any hours on it, I didn't suspect rings. I pulled the motor and took off the head. Sure enough, intake valve would stick at its nearly fully seated position. Removed the valve. It was bent. A very slight bend, just enough to keep it from seating well. The stem had a spot of pitting and I could see from the wear on the tip that it had not been rotating. Talked to a mechanic I know. He said it was likely sitting for a long time and probably in the position where the intake valve was slightly open. It built up a little corrosion on the valve stem and when it was kicked over after storage, the valve stuck slightly open until the piston sent it home. That all makes sense and what I can see fits that narrative. So I bought a Pro-X valve and lapped it in. Reassembled everything and used a 42 pilot jet. Purrs like a kitten now.

Good find. That's very unusual. I've heard of these bike sitting for years and years and once the carb is resurrected they start right up and run great. Glad you resolved it.

Ken

Monday morning, ran perfect COLD until warmed up 3-4 minutes, then started to hesitate and stumble off idle..............
Help

Hi Willevok,
Welcome to the site!
It is always best to start a new post when we are talking about a new bike especially some time after the original post. It just stops people thinking about the first bikes problems even if they are similar.

Back to your bike.
What sort of temperatures are we talking about?
How old is the fuel, spark plug and is the filter clean and not over oiled.

Did it start on choke and I assume you backed that back to normal setting as it warmed up.
Did it rev ok without snapping the throttle open?
Is this a new problem?

Just need a bit more info to understand what your bike is doing.