Poor Starting Diagnosis.

"Unreliable starting and tick over are normally associated with fuel and possibly ignition problems rather than bottom end and Piston / cylinder wear, although I wouldn’t rule them out. I suggest that you try the following solutions before doing any major surgery on the motor and certainly before considering replacing the crankshaft. Also I have often discovered that an inappropiate starting method is being used so I usually refer pilots who are having problems starting their Top80 to read my article on starting.

1. Use the best fuel that you buy. At least 97 octane or better still use Shell’s top fuel I think they call it V-Power or some such, this is reported as being 99 octane. The engine runs better and cooler with these fuels.
2. Use fresh clean fuel. Ensure there is no water in the fuel tank. In my experience modern fuels are going off after 6 to 12 weeks depending upon how it is stored, plastic containers seem to make it go off the fastest, metal jerry cans stored in a reasonably constant temperature are the best.
3. Check the choke isn’t on!
4. Set the carb’ mixture screw to the default setting of one and a half turns out.
5. Set the tickover to approximately 2100 to 2300.
6. Change the spark plug and set the gap to 0.5mm.
7. Replace the inline fuel filter.
8. Check the integrity of the stop wire and switch.
9. Have you changed the storage conditions for the machine, could it be getting damp? Spray electrics with moisture repellent.
10. Is the plug cap secure on the HT lead?
11. Is the HT lead secure on the coil?
12. Is the HT lead in good condition, ensure it hasn’t become chafed through.
13. If the ignition looks dodgy then replace the coil and plug cap.
14. Replace the diaphragms in the carb’.
15. Have the carb’ “Pop off” pressure checked.
16. Check the reed valve isn’t damaged.
17. Refit the carb using a small amount sealant to prevent air leaks and ensure that the pulse transfer hole doesn’t get blocked in the process.
18. Is the compression OK, check the piston ring is free in its slot. If not then clean the slot to free the piston ring.
19. Replace the piston ring if it is damaged or you suspect the compression is low.
20. Check the crank shaft seals aren’t leaking.
21. If you have done all these and there is evidence of a seize then replace the cylinder and piston.