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xr250 runs like two stroke

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I recently acquired 1987 xr250 from a friend, he said that it may not run right because it had been sitting for some time (around 3 months). It idles fine, has power, but it doesn't want to stay at a steady rpm (it surges really badly).

So I took it home, dropped the bowl, cleaned out all the passages. It seemed in pretty decent condition, but at least I know what it's like in there. Kick it over, ride it down the road, and it didn't solve it. I drained all the gas, replaced it with new gas, and still runs like crap.

The best way i can describe it is that it runs.. like a 2 stroke. It either wants to be at full open throttle, or no throttle. Holding the throttle at steady rpm, it just kicks and surges.

What cold cause it? I've just cleaned the air filter and I'm letting it dry. My next suspicion is the fuel filter that's on it.

Thanks for any advice:worthy:

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Start with the obvious first. Did you REMOVE the jets and clean them? Are the boots on the intake and airbox cracked or leaking? Try running it without a fuel filter?

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Start with the obvious first. Did you REMOVE the jets and clean them? Are the boots on the intake and airbox cracked or leaking? Try running it without a fuel filter?

Yup, I removed both things that I saw, unless I missed one (that might explain something). I'm pretty sure it was the main jet, and the other looked like whatever the needle sat in.

I don't see any cracks in the airbox. I just replaced some of the fuel line, as it was of really small internal diameter, with some thicker stuff. That seemed to help the problem, but it still has hesitation in the mid range.

Is it possible that the muffler is the cause of my problems? The insert seems to be taken out, as the "inner muffler pipe" seems to be gone.

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Post what sizes your jets are. The Hex jet is the main and the round one is the pilot jet.

Did you pull the fuel screw and clean that passage? Be careful not to lose any parts when you do. Should be screw, spring, washer, o-ring in that order.

With the exhaust baffle removed it will make jetting lean if the jetting is already sized to account for it.

Also need to know if the snorkle under the seat is still there and what air filter you're running.

Your elevation?

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Post what sizes your jets are. The Hex jet is the main and the round one is the pilot jet.

Did you pull the fuel screw and clean that passage? Be careful not to lose any parts when you do. Should be screw, spring, washer, o-ring in that order.

With the exhaust baffle removed it will make jetting lean if the jetting is already sized to account for it.

Also need to know if the snorkle under the seat is still there and what air filter you're running.

Your elevation?

The Jetting is- 130 main and a 40 jet. Is this right, and if so, what is the fuel screw supposed to be at? I'm around 3k feet. (tucson az)

The snorkel is off, and the air filter is old and raddy (slightly torn on the outside level in a couple of places). Whatever it is it's probably aftermarket and has 2 stages.

I didn't clean out the pilot jet the first time, it was hidden by the floats. It was clogged, but now is fine. The surging is gone.

However, it still has some hesitation in the midrange. It just doesn't feel quite like it should, it still feels 2-stroke-ish. Could this be an incorrectly adjusted fuel screw?

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1/4 throttle to 3/4 throttle(mid) is handled by the needle. Make sure its clean and not pitted , corroded , gummed up and its passage way is clean and clear.

A bread tie wire works great on the pilot jet and a small drill bit works on the main jet to clean them out. Also the needle jet holder , directly under the main jet , has a bunch of little holes in it , a bread tie wire works good on them too.

Start with 2 turns out on the fuel screw , if you go more then 2.5 turns out go the next size bigger jet , more then 1.5 turns in go smaller.

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1/4 throttle to 3/4 throttle(mid) is handled by the needle. Make sure its clean and not pitted , corroded , gummed up and its passage way is clean and clear.

A bread tie wire works great on the pilot jet and a small drill bit works on the main jet to clean them out. Also the needle jet holder , directly under the main jet , has a bunch of little holes in it , a bread tie wire works good on them too.

Start with 2 turns out on the fuel screw , if you go more then 2.5 turns out go the next size bigger jet , more then 1.5 turns in go smaller.

How do you pull the needle? On my drz the needle is on top, I opened that on this bike and it's just the mechanism for the throttle. I blew out the jets with 100 psi, so they should be good. I sprayed some carb cleaner up in the needle's passage, but it wasn't very accurate.

I'll try 2 turns on the fuel screw, hopefully that helps some.

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I've fiddled with the fuel screw, and I've determined that it must be rich. It's running slightly better when it's backed all the way to 0 turns out.

What is the stock jetting for the xr?

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