just done a compression test on my 1979 xs 250...left bore 120 psi...right bore 160 psi..is that good or bad.... advice please guys. 

160 is high, 120 is ok but 140 - 150 is best.

 

did you try with oil in bores to see if its ring wear?

 

I suspect you need a decoke

You really need the readings from the manual that tell you what it should be, then compare it to what you have, a difference in the amount usually means more wear in one barrel or rings or valves than the other but they all have minor differences, it just depends if your still in the correct range that the manual says you should be. Your difference could be for example from slightly more carbon in one valve seat than the other, might just need a clean, have you ever used an upper cylinder cleaner like RED X for example? These can help with most minor differences. Try using a higher grade fuel and a UCL for a couple of weeks and see if the differences just go away. Don't fret over it as it's more likely to be a minor cleaning than anything serious.

40 minutes ago, drewpy said:

160 is high, 120 is ok but 140 - 150 is best.

 

did you try with oil in bores to see if its ring wear?

 

I suspect you need a decoke

thanks d

39 minutes ago, slice said:

You really need the readings from the manual that tell you what it should be, then compare it to what you have, a difference in the amount usually means more wear in one barrel or rings or valves than the other but they all have minor differences, it just depends if your still in the correct range that the manual says you should be. Your difference could be for example from slightly more carbon in one valve seat than the other, might just need a clean, have you ever used an upper cylinder cleaner like RED X for example? These can help with most minor differences. Try using a higher grade fuel and a UCL for a couple of weeks and see if the differences just go away. Don't fret over it as it's more likely to be a minor cleaning than anything serious.

thanks s