We have very many two stroke machines brought in each year with starting issues. Of course there could be very many reasons for this but by far the most common cause is stale fuel.
In fact around 8o% of small engine issues are due to using stale fuel, but very few people and even some engineers are still unaware of the fact that petrol has a very short shelf life. In fact the fuel brought from garages these days only has a shelf life of around 60 days max. After this time the fuel has generally degraded sufficiently to gum up fuel systems as well as attack soft materials in the fuel systems, causing expensive damage.
Oil companies are under more and more pressure to extract more fuel from every barrel of crude, which is leading to a poorer quality fuel. This modern petrol is made up of more than 100 chemicals, roughly a third of which are Aromatic Hydracarbons (solvents). It is these solvents that give petrol its signature 'heady' smell, but these chemicals are also responsible for the rapid degradation of the petrol. At times this fuel can degrade to an unacceptable level in as little as a month, after which time the ability to start an engine will be compromised and power will drop when started. The stale fuel also starts to slowly dissolve soft materials such as rubber fuel hoses, plastic fuel tanks and aluminium carburetor parts.
The safe storage life of 'pump'petrol is now only around one month, although tha actual rate of degradation depend on heat, light and humidity. Storage of cans in a cool, dark and dry cabinet will extend the life of petrol, whereas the fuel cans left basking in the sun and dripping in the rain or dew, will degrade the very fastest.
However, the stale fuel issues can be a thing of the past if you use Aspen alkylate fuel.
Aspen 2 is a ready-mixed (2%) alkylate petrol for all 2-stroke small capacity engines with a recommended mix of 2% or 1:50. It is mixed with a synthetic high quality high performance 2-stroke oil for maximum protection and low smoke. This 2-stroke ready-mixed alkylate petrol contains no sulphur, benzene or aromatics. It is therefore much better from a health aspect to use than regular petrol. In fact normal petrol contains so much benzene and aromatics (read solvents) that it is a real health risk to use in 2-stroke engines. Aspen 2 is also chemically inert so you can comfortably leave the fuel in the machine and it will not gum-up. It will also store for years whereas normal petrol start to go off after 30 days.
So it is well worth exploring the fuel related problems before getting too involved in other mechanical investigation