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2003 CR250 making abnormal noise

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I just bought a 2003 cr250 that looks to be in great shape. He claimed it had low hours, and it seems like it does. It has good compression and starts first kick every time. Even in -15 degrees celsius. (5 degrees F) On my first ride with fresh gas, mixed at 32:1 with opti 2 cycle oil, it seemed to run great. The second ride I notice a rattle in the engine when just cruising at half throttle or speeding up through the mid range. Today I took it out for a ride in the snow and realized something was wrong. When riding in the snow, it seemed I couldn't even rev it too little or too much without the engine rattling. Usually I can ride good low and high, but in the middle of the power accelerating or cruising, it rattles a bit. But now it rattles A LOT. It still idles fine without any noise. I just payed fully for this bike with the cash that I have saved up for 5 months. When you just spent $2000 on a bike at 15 years old, you sh*t your pants. I really would appreciate feedback. And before you mention it, my dad was with me and looked over the bike when I bought it.

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it sounds to me like you better start tearing it down and checking things out,could be a number of things,none of it good if keep riding it

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Your needle jet is probably set too lean, try moving the clip one spot down. Mine did the same thing. The jetting on the newer CR's is very finicky.

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Yes try moving your clip position on the needle to richen up the the mid range. It sounds like your running lean & could ruin the motor if you continue to run it. At 5 deg. I'd rather be on the rich side of my jetting than lean. Do you know what your current jetting is & did you get a manual with the bike ? If not, I highly recomend investing in one & reading up on your bike.

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I have a manual, and it says the stock position is 2. For my sea level and temp it still recommends 2? Air screw is also the same stock and recommended. I already put in a little extra oil then I needed, but I will try and see what happens.

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If your at sea level & 5 deg the manual recomends the jetting below.

AS - 1 1/4

PJ - 35

Needle - 6BHY38-72

NC - 3rd

MJ - 450

I have a manual, and it says the stock position is 2. For my sea level and temp it still recommends 2? Air screw is also the same stock and recommended. I already put in a little extra oil then I needed, but I will try and see what happens.

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I'm in between 750 and 1500m above sea level. The temp in Canada is so unpredictable, as 2 days ago it was 60 degrees and sunny, now 5 and blizzarding...... But soon it will be between 19 and 60 degrees. It recommends

AS: 1-1/2 to 1-3/4 turns out

SJ: 30

NC: 2nd position

MJ:420-410

Jet needle 6BHY38-73

Which is what it's set at right now.

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Ok.. At 750m-1500m & 5 deg. it recomends.

AS - 1 1/2

PJ - 32.5

stock needle & clip position

MJ-430

With your change in temps keep an eye on your jetting to avoid damage to your motor. Congrats on your purchase.

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Good to hear you got it sorted out.. The jetting guide in the manual is a good place to start but it sounded like the motor was letting you know it was lean in the midrange.

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