Honda TRX250R Forums banner
1 - 20 of 20 Posts

·
Registered
Joined
·
25 Posts
Discussion Starter · #1 ·
So I just put in a new 68mm wiseco with a fresh bore. I put the cylinder and head on and was only getting about 90lbs compression and could hear air leaking past the piston rings. Is this normal before breaking an engine in and what kind of compression should I get the rings seated?

Thanks.
 

·
Registered
Joined
·
25 Posts
Discussion Starter · #3 ·
nope took off the cylinder and the rings are good. Isn't 165-185 a good compression for a properly broken in engine, but what should it be for one that hasn't even started yet after a fresh top end install.
 

·
Registered
Joined
·
137 Posts
did you have the throttle wide open when you did the test?
 

·
Registered
Joined
·
4,160 Posts
what year piston and crank are you using. Are you using a spacer plate? If you have lets say a 87-89 piston and a 87-89 crank, you do not need to run a spacer plate. But if you run a 86 piston with a 87-89 crank you will need the spacer plate.

The reason i ask is if you use a spacer plate when its not needed it will darasitcly increase your squish area at the top, thus lower compression.
 

·
Registered
Joined
·
25 Posts
Discussion Starter · #8 ·
yes throttle was open but motor was cold and hasn't been run at all yet. i'm using all 88 parts with no spacer plate.

for compression testing should I kick it once then bleed the air or should I keep kicking until the pressure stops rising?
 

·
Registered
Joined
·
83 Posts
yes throttle was open but motor was cold and hasn't been run at all yet. i'm using all 88 parts with no spacer plate.

for compression testing should I kick it once then bleed the air or should I keep kicking until the pressure stops rising?
Kick it until the pressure stops rising, if your compression is still that low i would take the rings off the piston and place them in the cylinder and use feeler gauges to check ring end gap, did the cylider get the bore matched to the new piston?
 

·
Registered
Joined
·
25 Posts
Discussion Starter · #10 ·
yes the cylinder was bored to match the piston and the ring end gap was in spec, but is it normal for air to seep past the rings on a fresh install before the rings are seated?
 

·
Registered
Joined
·
4,160 Posts
That wont matter. Just keep kicking till the gauge stops rising.
 

·
Registered
Joined
·
83 Posts
yes the cylinder was bored to match the piston and the ring end gap was in spec, but is it normal for air to seep past the rings on a fresh install before the rings are seated?
what concerns me is that you can hear it...i would do a leak down test and make sure its not leaking somewhere else, head and base nuts are torqued? Reed cage is tight? I assume you, used, all new gaskets?
 

·
Premium Member
Joined
·
13,281 Posts
Assuming the cylinder is bored/honed correctly and the piston to sleeve clearances and ring gap is good...perform a leak down test of the engine and an engine coolant system leakdown as well. Only real way to find out you have no leaks.

Carlos
 
1 - 20 of 20 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top