aleyesonme Posted June 25, 2012 Report Share Posted June 25, 2012 ok ive searched but havent found the answer to my question. ok i have +4 timing, hjr dune port, .030 milled stock head, and at 770 feet elevation. i have seen the psi to elevation chart and i believe my heads are equal to a 21cc domes. and im getting a reading of 120 psi on both cylinders. does that seem to low for my setup??? the reason im asking cause my bke has being running phenomonal till yesterday, started bogging out the hole in second gear and it has neva done that and check the compression today. and it just seemd low compared to the chart. i know stock it should be reading 125psi but mine not stock. does anyone have a similiar setup or know what i should be reading??. thanks Quote Link to comment Share on other sites More sharing options...
Jereme6655 Posted June 26, 2012 Report Share Posted June 26, 2012 While you DO have a milled head.....your compression is not really that far off. This is because of the different port timings....basically when you grind out metal for the port job it will lower your compression and the milled head is to bring you back up towards good compression... Quote Link to comment Share on other sites More sharing options...
Surfrjag Posted June 26, 2012 Report Share Posted June 26, 2012 your compression should be closer to 150 with 21 cc domes. the porting does effect it some but not 30psi difference. i think a head milled .035 is equal to about 20.5 cc . sounds like its time to freshen that topend up imo. unless your not holding the throttle wide open and kicking till the needle stops Quote Link to comment Share on other sites More sharing options...
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