03 RM 250 compression supposed to be at ?

Tbangbangftw
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Tbangbangftw
I have 03 RM 250 and it feels like it losing power . I recently put a new head on it because my old one had been cracked from previous owner . It also has newer piston and rings I put in when I bought it . I compression checked it today and it has a 120 psi . I can not find anywhere what my compression should be . I never checked when I did the new piston to see what it was then so I trying to figure out maybe it's time for new piston and rings ?
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Paw Paw 271
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Paw Paw 271 3/19/2017 3:47am
3/19/2017 3:47am
120 is very low. You should be above 180.
Are you sure you have the correct head?

Paw Paw
HackMan162
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HackMan162 3/19/2017 8:09am
3/19/2017 8:09am
ALso, how are yo doing your check? Throttle open, 4-5 kicks, record the best. And like PawPaw said, verify the head part number matches the corresponding cylinder part number. The should both be cast into the part.
Monk
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Monk 3/19/2017 12:08pm
3/19/2017 12:08pm
Over 200psi...
BobPA
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BobPA 3/19/2017 1:48pm
3/19/2017 1:48pm
Monk wrote:
Over 200psi...
Not on a stock two smoke...

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Monk
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Monk 3/19/2017 1:54pm
3/19/2017 1:54pm
Monk wrote:
Over 200psi...
BobPA wrote:
Not on a stock two smoke...
Yup, literally finished up a 15 300xc top end last week. Tested at 215...

Every YZ 250 I've owned had been well over 200psi when stock. My Harris Performance YZ 250 which was ported with the head shaved (unmodified dome) tested at 238psi...
Tbangbangftw
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Tbangbangftw 3/19/2017 2:21pm
3/19/2017 2:21pm
Yeah part number matches old one . But no I did not know about holding throttle wide open when I did it . I will try that and see were it's at .

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