Thanks everyone, I appreciate its hard to diagnose stuff without being here and it doesn't help that I'm not really a bike person! I'm working my way through all he suggestions, the exhaust is connected properly and does have a gasket, and I don't think its blocked. Its had oil relatively recently. I have also ordered a new spark plug. I have found that it had no air filter so not sure if that could be the cause? I didn't think it would effect it that much! The carb was cleaned by a professional so I don't think that is the problem. It has a CDI unit, but that seems to be working ok? I mean it starts every time even when its been stood for 6 months (but im no expert). I don't have a lot of money to spend on it, and I would like to try and do any of the work myself so I could learn for the future, but I'm quite reluctant to attempt to take the engine apart as I fear I will bugger it all up! is it as hard as I imagine? or could a beginner do it, using youtube?