Hard to start after riding for awhile?

[fredt]

Please don't criticize me too much if you see this on another forum, I have to try here since I get no response anywhere else.

I have an old WR3, 650cc. that I use for the grandkids.
Compression is good.
Carb rebuilt - twice.
New battery.
This ski runs good until you take a break and try and restart. Then it may, or may not start. It turns over good, acts like it will start but most of the time I end up pulling it to ramp with another ski.
I put it on the trailer, get it home, hook up flush hose, and BAM! it starts.
I've checked almost everything and am really frustrated.
I haven't checked the reeds.
Could it be the fuel pump side of the carb? All the rubber looked good so I didn't replace the parts in there.
How about some fresh ideas.
I'm a fair mechanic and not opposed to trying most anything.