hello i just bought a race ready suzuki rm80. everything is pretty much raceing on it except it has a stock exaust. yesterday when i got it i rode it for about 3 hours then and put it in the shed and this morning i got it out and it wouldnt start. i figured it was a fouled out plug and it was. i changed it and it started first kick. i rode it for about a half an hour and the new plug fouled out. the previous owner said the bike has had a history of fouling plugs. any idea why this is happening?