Won't Idle 250x

2006 CRF250X

Valves checked and within spec

Previous owner had let the bike sit for 4 years, fuel drained, supposedly.

Bike ran OK but would not idle and was hard to start.

Found a deteriorating air filter and replaced.

Replaced petcock. Would not shut off fuel flow.

Replaced all three fuel lines.

Rebuilt carb (Stock jets).

Bike now starts and runs but can't get it to idle. The idle screw is all the way in. No more adjustment left. If you hold slight pressure on the throttle, the bike runs fine.

Any ideas or thoughts would be great.

carb slide. On the back is a thin membrane sandwiched between a plate. It can deteriorate from time, carb cleaner ...etc. It causes the slide to hang up when it should close. I went thru this a few years ago. Two experienced mechanics (one a honda facotry supercross wrench) couldn't figure it out. Finally my neighbor put the carb on a bench and pulled it apart piece by piece. He used rubber cement to reattach it. Worked fine after that.

The Titanic was built by experts, the ark by a layman...

Shame on me.

I looked at that membrane but did not touch or replace it.

I will replace and give it a try.

Thanks for the information.

Wellll,

Even with that slide plate seal missing, it should not in any way prevent the slide from dropping all the way.

Besides, if it were hanging up, your idle would be HIGHER, not lower.

You made no mention of the fuel screw. The fuel screw adjusts the pilot circuit, which IS the idle.

Turn your fuel screw until the idle goes up. The drop the idle and repeat.

The idle cable can stretch , and not longer turn correctly, or even break.

carb slide. On the back is a thin membrane sandwiched between a plate. It can deteriorate from time, carb cleaner ...etc. It causes the slide to hang up when it should close. I went thru this a few years ago. Two experienced mechanics (one a honda facotry supercross wrench) couldn't figure it out. Finally my neighbor put the carb on a bench and pulled it apart piece by piece. He used rubber cement to reattach it. Worked fine after that.

The Titanic was built by experts, the ark by a layman...

:smashpc:

I have tried to adjust the fuel screw with no results.

Started at 2 turns out. Went all the way to 4 turns out with no change. Went to 1 turn out with no change.

The idle screw is turned in (Spring compressed all the way) as far as it would go with no change in idle speed.

Either way, I ordered a new seal and extended fuel screw so I plan to pull the carb and install the parts. I should have done all of that before.

This bike is new to me so I am learning as I go. Even with the shop manual.

Would the throttle position sensor make a difference in position? I marked and replaced it exactly where it was when I took it apart but just looking for options. The manual says "No adjustment necessary" but who knows. It has a slotted screw hole for a reason, right.

Anyway, Thanks for the insight / information. It all helps.

I have tried to adjust the fuel screw with no results.

Started at 2 turns out. Went all the way to 4 turns out with no change. Went to 1 turn out with no change.

HAVE YOU INSPECTED THE FUEL SCREW TIP AND ORING / WASHER?

The idle screw is turned in (Spring compressed all the way) as far as it would go with no change in idle speed.

WHAT DO YOU MEAN SPRING COMPRESSED? IT IS A CABLE OPERATED IDLE SCREW, WITH NO VISIBLE SPRING....

Either way, I ordered a new seal and extended fuel screw so I plan to pull the carb and install the parts. I should have done all of that before.

This bike is new to me so I am learning as I go. Even with the shop manual.

Would the throttle position sensor make a difference in position? I marked and replaced it exactly where it was when I took it apart but just looking for options. The manual says "No adjustment necessary" but who knows. It has a slotted screw hole for a reason, right.

NEVER DISASSEMBLE THE TPS. IF YOU DID, YOU NEED TO RE-CALIBRATE IT. IT HAS NOTHING TO DO WITH IDLE!

Anyway, Thanks for the insight / information. It all helps.

"HAVE YOU INSPECTED THE FUEL SCREW TIP AND ORING / WASHER?"

Yes. Replaced with all new parts during the rebuild.

"WHAT DO YOU MEAN SPRING COMPRESSED? IT IS A CABLE OPERATED IDLE SCREW, WITH NO VISIBLE SPRING...."

There is a spring at the end of the cable covering a portion of the screw that keeps pressure on the screw. That spring is totally compressed so there is no more adjustment left.

"NEVER DISASSEMBLE THE TPS. IF YOU DID, YOU NEED TO RE-CALIBRATE IT. IT HAS NOTHING TO DO WITH IDLE!"

I did not disassemble it. I removed it and replaced it in the exact same position during the rebuild as per the shop manual. I was just wondering if it may be part of the problem.

Thanks

Edited by Fyrflie

Poor idle is almost always a lean low speed mixture from a dirty carb, or a mis adjusted mixture screw. You said the bike sat for a long time which is #1 clue to a dirty carb.

So I suggest a thorough carb clean, especially the small discharge ports in the floor of the venturi, also check the float level.

TPS info is used to adjust part throttle ignition timing, not unlike the vacuum advance on a carburetor car.

Thanks Chuck.

I did rebuild the carb and surprisingly enough, it looked really clean inside for supposedly sitting for 4 years. The owner did say he drained the bike of fuel but to what extent I don't know.

I am going to pull the carb again and give it another once over. It is possible that I missed something.

I did also check the float but I don't have a float tool so my measurement was fairly rough.

I took the bike out yesterday. I did notice that fuel was dripping slightly from the carb overflow so the Float may be out of adjustment. Would you concur with that ??

Thanks for the info.

Scott

Float too high, or a bad float needle, or a bad float needle seat, or a bad float needle seat o-ring.

Float too high, or a bad float needle, or a bad float needle seat, or a bad float needle seat o-ring.

Now that you mention the Float Needle Seat O-Ring, I don't remember removing and replacing that.

I will check it / Replace it when I pull the carb out again.

As you can probably tell, I am a newbie when it comes to carbs. This is only the second one I have rebuilt so I am still learning as I go.

I appreciate all of the input given thus far. It truly does help.

Scott

Okay guys. Here's the final report / outcome to the poor idle problem.

I removed the carb again and replaced the Carb Slide Membrane / O Ring.

Removed all of the jets and blew out all of the orifices.

Checked and double checked the float level.

Re-assembled everything including a new adjustable Fuel Mixture Screw.

The bike now runs perfectly. Fuel mixture screw is two turns out as per the Honda Shop Manual.

Thank you all for your contributions and suggestions. It has helped tremendously.

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