I recently purchased a 97 gp 1200 with a sbt motor in it, it was running great and pretty much flawless the first few times out, it seems lately to bog down a litttle with a slight(sometimes moderate) loss of engine power. other than these periods it runs hard and will do top speed. sometimes while turning but also while going staraight. My buddy flipped it over and it seems to do it more lately after that.. did a compression check about 4 running hours ago(122 psi each), filled the oil,changed the plugs, and used 87 octane pump gas. any suggestions? thanks in advance.