compression loss on yz250f

Joined
Aug 9, 2007
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#1
ok i have a yz250f and i gave it a fresh oil change this morning and then i filled the coolant in it and then changed the sparkplug... i had compression all up untill i changed the spark plug. when i kicked it i can do it with my hand there was a huge loss of compression. i put the old 1 back in and i still got the same thing . im lost
 
Joined
Jan 27, 2000
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#2
Before you changed your plug, did you clean the dirt from the area around the plug cap and the cavity that the plug sits in? If not, there is a good chance that dirt got into the cylinder when you removed the plug. Dirt and water can collect under the plug cap if the plug cap is not sealed properly or is damaged. You have to take compressed air and blow the dirt out before removing the plug. Also, make sure the little drain hole at the bottom of the plug cavity is clear. This lets the water out.

Do a leak-down test to check your compression.
 
Joined
Aug 9, 2007
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#3
ya i just push started it down my street and it started up and got its compression back and runs better than it did be4 thanks tho
 
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#5
i raced it tonight and it ran great i think taking out the spark plug took away the compression it had and needed to be started again to regain compression. its not like the new bikes that have the auto decompression mabie that has something to do with it