Hi i recently bought a jog rr 2007, but it seems to have no bottom end power at all, I knew the previous owner so I know abit about whats been done to it. It was derestriced from new and rode with a standard exhaust, Then a technigas exhaust was fitted. I'm not sure if the fault started when the exhaust was changed but i do now that when the exhaust was changed it did not have a bigger main jet or new rollers fitted at the same time. When the bikes going along a flat road it struggels to get to about 30mph but then picks up to about 45 really fast??? Ive cleaned out the carb, replaced the spark plug and cap and cleaned the air filter but still the same. Do i need to replace the main jet for a bigger 1 as the exhaust was changed? Also what weight rollers are required or where can i find out. Any help would be really appreciated cheers