hi i have got a adly herchee cat 50 derisricted and when it gets to 10mph it losses the revs this is the second time it has done this the first time i had changed the petrol filter and cleaned the air filter and that solved the problem back to 40mph and yesterday it started again so i cleaned out the air filter again and still hasnt got better if you have any suggestions on how t fix this let me know many thanx cameron