Welcome to the forum and you can see already there is plenty of advice. You have definitely come to the right place.
I'm with Sesman on this, check the valve clearance first, it really is easy to set them incorrectly and not realise because the clearance is so small and you think it is on compression and actually it isn't!
If that doesn't work take the rocker cover off (after first slackening the valve adjusters right off to avoid causing damage when you put it back on as you'll be trying to put the valves under compression as you do the mounting bolts up) and check the valve timing is correct using the sprocket marks. When you replace the rocker cover use a torque wrench on the bolts because they are really easy to strip.
Good luck and report back how you get on👍
