Unless someone has altered the timing I doubt it, you need to remove the valves and check the condition and grind them inHey guys, it seems to suck through the exhaust... Do u think that this could be down to incorrect valve timing? If so i think i willneed to find some way of determining what the timing currently is..
Snoopers right, blowing back thru carb sounds like inlet valve probs unless ignition timing is way to far advanced.i do remember you saying it was blowing back through the carb, if this is the case while you have it stripped I would remove the valves and give them a quick go with some grinding paste and it will give you chance to inspect the seats for damage