Just thought Id share a problem and its fix just incase it happens to anyone else, I am currently running a gas gas tx 250 1998, whilst riding the bike developed a loud rattle and pinkin, especially under load. Straight away I thought (main bearings) as the sound seemed to come from the flywheel area. After dropping the engine and having it rebuilt with new bearings and seals ,I ventured out again to find that the noise was quieter but still their, (bearings were on way out but not totaled). After reading up on the net, i found a site that had a blog about negatives of using low grade fuel. It suggested trying the OPTIMAX higher grade fuel. I drained the tank and refilled with the optimax and would you beleive it actually worked. The engine now runs sweet as a nut. I rang gas gas uk as I thought the timing may need adjusting slightly but they informed me that it cannot be adjusted on my bike. I have been running the optimax now for 3 months with no problems and a definate spike in low end torque.

Thanks 3006phil

Yes your fuel has a lot to do with it. I've ran 112 octane mixed with 89 octane 50/50 for years and had no problem. Some nut told me that the 101 unleaded would give me more pop off the bottom, well it did but the wrong kind it ran like crap the next event.