My 1970 Yamaha Scrambler 125 isn´t working very well. I put it in 2nd and it bogs down. I figured it´s due to poor compression. I ran a test and am only getting 55 psi. I have heard that that is almost always too poor of compression, but for older bikes such as this, it may be alright. I don´t have the owner´s manual. Is this a compression high enough to run the bike?