what is a good brand four stroke motor?

So.... long story shortened, my first bike came with a two stoke already installed. I ran it for several THOUSAND miles before a minor spill left the motor dead. I replaced it with a 4 stroke... which turned out to be a nightmare of constant issues. (It was a houshang titan.) I had to put a better, heavy duty clutch on it, and a sealed clutch case which the original did not have. (It was some home made bit of tin over it, let in all manner of road gunk.) Ran it for one year before it started getting issues. I adjusted, tweaked, cleaned, replaced assorted parts including the carb.
And it simply WILL NOT start. It's sat now for a few years.

I'm giving up on it. I cannot figure out what went wrong, perhaps once I get it off I MIGHT find a mechanic willing to help diagnose what happened so I can know what to look for next time.... But as for me fixing this? It's just not happening.

Meanwhile.... please put in your best suggestions for what brand to replace it with? Please post, and explain why too.

And heads up, please DO NOT suggest anything that only bikeberry sells. I had a very bad experience with them and do not plan on every buying from them again.
If you want I will fix your engine for free unless it needs parts , which I doubt.
Its far better to fix what you have.