Low Compression

i tested my 88 kx 125 for compression and the reading came out as 85 psi. the cylmer manual said it should be around 103-171psi.I tried when the engine was cold and at operating temp.I checked the top end and it was perfectly fine, i have the jetting right on, and can't find any air leaks. I s there any other way to find why this has such low compression. all my friends tell my that the bike should be "throwing me off the back", . also the cylinder wall looked fine, but i heard some where that if you hone the cylinder your will get alittle more compression out of it. :bang: