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FCR probelems, lean, lean, lean.

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I give up on this wretched thing. My kid left the gas on all summer with the bike sitting and I cannot get it to idle nor run properly on the main. I've soaked it in brake cleaner, zylene, boiled it in hot soapy water, nothing has worked. All the passages seem to be perfectly clear when I blow them out or shoot carb cleaner through them.

It absolutely will not run without overheating and backfiring unless the choke is on. Float level is correct. Heck, maybe it isn't the carb but I have no intake leaks.

Any ideas? Is there anybody that properly overhauls these things or should I play carb baseball with the miserable thing?

If so what years will work on an 04? I've never had any mechanical thing in my life piss me off as much as this carb I've been screwing around with for the last two months. :bonk:

PS: Will the FCR off an 08 250sxf work on an 04 400exc?

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You don't need a new carb.

You have to verify several basic things:

- that you have a brand new pilot jet

- that the pilot jet passage is clear all the way through

- that the hot start and choke plungers are clean and free of corrosion

- that the accelerator pump nozzle is not clogged (lift up the subframe and watch it work....)

- that the fuel screw o-ring is not damaged

- that the accelerator pump diaphram is not damaged.

You can repair/replace all of this in a couple of hours.

Good tutorial

http://www.dirtrider.com/tech/141_0707_keihin_fcr_carb_rebuild/viewall.html

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You don't need a new carb.

You have to verify several basic things:

- that you have a brand new pilot jet

- that the pilot jet passage is clear all the way through

- that the hot start and choke plungers are clean and free of corrosion

- that the accelerator pump nozzle is not clogged (lift up the subframe and watch it work....)

- that the fuel screw o-ring is not damaged

- that the accelerator pump diaphram is not damaged.

You can repair/replace all of this in a couple of hours.

Good tutorial

http://www.dirtrider.com/tech/141_0707_keihin_fcr_carb_rebuild/viewall.html

Checked every single item repeatedly and did a complete teardown except for the jet block. You pretty much listed basic carb 101. I'm beginning to wonder if I might have an internal gasket failure. It honestly acts like I have a serious intake air leak versus just lean but I don't.

I've overhauled dozens of FCRs but this one has me stumped. I wish I had a spare. I'm not even too sure now there isn't an issue with the engine.

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Checked every single item repeatedly and did a complete teardown except for the jet block. You pretty much listed basic carb 101. I'm beginning to wonder if I might have an internal gasket failure. It honestly acts like I have a serious intake air leak versus just lean but I don't.

I've overhauled dozens of FCRs but this one has me stumped. I wish I had a spare. I'm not even too sure now there isn't an issue with the engine.

Contact James at JD. He stocks the split-body seals and the other obscure FCR stuff.

GOOD LUCK

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Contact James at JD. He stocks the split-body seals and the other obscure FCR stuff.

GOOD LUCK

Heck, I'll just send him the carb, problem solved (if it's the carb).

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Make sure the slide is not installed upside down:

FloatingValve.jpg

:bonk:

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UD, did you ensure the oil is fuel free? Fuel left on is known to get into the cylinder, get past the rings and dilute the oil. The fuel fumes them cause major running issues (let alone, make for weak oil).

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