Does it rev cleanly up to the redline when in neutral? If not try these first.
Check air filter is clean, if not change it.
Check petrol filter is clean, if not change it.
Clean and regap the spark plugs, these might need replacing also.
If you are capable clean the carburetors.
Also check all the HT leads and spark plug caps.
Check air filter is clean, if not change it.
Check petrol filter is clean, if not change it.
Clean and regap the spark plugs, these might need replacing also.
If you are capable clean the carburetors.
Also check all the HT leads and spark plug caps.