Easy mate, no need to pull her down just yet. Swap the plug first and see where you go from there.
Honestly the motor came to me in several pieces in a box. The ring was stuck solid in the piston, and it took several days in marvels mystery oil to break it free. I cleaned it up and the motor seemed to have compression. The carb is a piece of crap off a rovan that i believe may be faulty anyway.
The jug needs to be re-torqued anyway, and I was...suspect of the head gasket as is. I want another look at the ring and jug surface anyway, and will replace to gasket while I'm going. Today was a temporary bolt up to see if it would run.
Start with a new plug and re set the H & L to factory
Definitely re-set the needles when I moved the carb over to this motor, it did have a brief splutter when the pull start imploded, but never repeated when I put the other pull start on....that one is, unfortunately, elderly, not working well, and I just gave up and ordered a couple of spares.
I do not think this carb is metering right on the low needle, but it's off a clone motor that I think the previous owner ran somewhere just lean of "plug BBQ". I've had the 900 series carbs on my other bajas in the past, went ahead and started fresh with one while I was eliminating problems instead of flailing with a suspect carb. If the motor runs well with the new carb, I will put this one one and test it as a back up carb, or maybe resurrect the poor old OBR 2-bolt I still have from years ago
This was it, slightly worse for it's trials and tribulations.