XR50 hanging idle/ air leak?

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9/10/2017 10:43 AM

Picked up a 2000 XR50 that had been in storage for several years.

Replaced the clogged petcock, dump some fresh fuel in there and it runs, but acts like it has an air leak. The idle stays really high, until it drops down enough to just stall out. Riding it is far more exciting than it should be, as chopping the throttle does not result in the rpm's dropping down right away. Throttle cable is fine.

Picked up a Honda carb rebuild kit, along with the 3 o-rings that go between the head and the carb. Replaced the gasket in the cap. Dismantled the carb and let it soak for hours in Chemdip. Same rpm issue.

Put some Hondabond between the head/intake/spacer/carb, put a thin layer of grease where the dust boot goes into the carb top along with a bit on the screw top gasket. A touch of grease on the fuel screw and idle screw threads. No change.

Spraying brake cleaner at the various intake and carb points while it's running seems to have no effect.

Suggestions appreciated.

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9/10/2017 1:41 PM

Does adjusting the idle change anything?

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9/10/2017 2:51 PM

imoto34 wrote:

Does adjusting the idle change anything?

If I turn the idle screw in far enough, it'll keep running. However, that's at an rpm much higher than it should be, enough for it to take off without touching the throttle itself.

I've tried the fuel screw anywhere from 1 to 3 turns out. All the way in causes the rpms to climb up I've noticed.

Bike is stock, and low enough hours to still be on the original tires. I also replaced the air filter with a new one.

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9/10/2017 3:41 PM

Plugged pilot jet.

Paw Paw

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9/10/2017 4:50 PM

Paw Paw wrote:

Plugged pilot jet.

Paw Paw

XR50's don't have a pilot jet, just a tube with a fuel screw in it to adjust the flow. I've blown through the tube with pressurized air in both directions.

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9/10/2017 7:27 PM

The needle jet acts just like a pilot jet in those carbs. Each tine hole has to be open. If it set for a while those little holes will clog and still looks clear.

Paw Paw

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9/27/2017 11:29 PM

Update:

Well you called it Paw Paw. Clogged pilot.
Unfortunately, no amount of air pressure, carb cleaner, Chemdip, and welding tip cleaners could unclog the circuit. I thought it was clear of obstructions; but clearly I was wrong. tongue

$13 for a Chinese carb and it's running like a top. Although it's supposed to be a carbon copy, it's not. Very similar, but not the same. Still, bolting it up and using the included slide resulted it a perfect running XR50.

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9/28/2017 9:40 AM

Great news.....

Paw Paw

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