Motorcycle Repair: 2003 Honda XR 70, honda xr 70, petcock

Question
Hi Guys, My sons have the above model and we are experiencing a couple of problems at the moment. The bike runs perfectly when in a no load situation. The carby has been totally cleaned and rebuilt and the bike also has had a new plug and lead fitted. As soon as the bike is put into gear and ridden it pulls ok through its low range but coughs and splutters all the way through the mid and high range. Any suggestions of what could be causing this? The boys are keen to go riding before the holidays are up!

Cheers Scotto

Answer
Sounds like carb main jet.  It only takes a litte sediment in the gas tank to clog the main jet for a moment.  Also deteriorating fuel line or clogged fuel filter or petcock.  If it's not that then it might be an ignition problem.  Drop the carb bowl first and look carefully for tiny bits of sediment, rubber, etc.