PSI, whats better

W

wls

Member
Joined
Mar 8, 2005
Messages
140
Age
68
Location
Mid- Mich. (Harrison)
Lets say you have a motor, that has a 145 psi, each cylinder, for some unknown reason you do a top end rebuild, new pistons/rings etc. After breakin you do a test and come up with say 125, why would this happen, after all you have new parts. Does higher psi always make a faster sled? Does the lower psi, affect your clutching etc? Lets say your making 75 hp, with the 145, what effect in hp will it be now with 125, worse/better, same? thanks
 

Different elevation; different temperature; different days affect the readings you get using a compression guage. buy a leak down tester & you know exactly whats going on.They are not affected by the above
 
wls said:
Lets say you have a motor, that has a 145 psi, each cylinder, for some unknown reason you do a top end rebuild, new pistons/rings etc. After breakin you do a test and come up with say 125, why would this happen, after all you have new parts. Does higher psi always make a faster sled? Does the lower psi, affect your clutching etc? Lets say your making 75 hp, with the 145, what effect in hp will it be now with 125, worse/better, same? thanks
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Did you use the same tester? One that fills the plug hole deeper will give that much difference. Are the rings seated? I would say it is one of the two.
 
how does the lower psi affect the HP, would it be less? after all 125#'s not bad. thanks

Actually I went out and checked the compression this morning, cold motor, 136ish. getting there, may need more breakin time.
 
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wls said:
this AM, its at 147, on a cold motor, when should a person do it, hot or cold motor? I do three pulls, throttle open.
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It's healing itself! :)
It should be warmed up from cold but not hot. 4-6 pulls with the throttle wide open. I bet it's fine. Also, being down that far from correct would be bad. Compression is very important to a 2 stroke. They start poorly, perform poorly, run hotter, and get worse fuel mileage.
 
dynofun said:
It's healing itself! :)
It should be warmed up from cold but not hot. 4-6 pulls with the throttle wide open. I bet it's fine. Also, being down that far from correct would be bad. Compression is very important to a 2 stroke. They start poorly, perform poorly, run hotter, and get worse fuel mileage.
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Tomorrow I'll let it warm up a bit and see what it says. thanks
 
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