It had a twist throttle when I bought it about 10 years ago. It has off-brand aftermarketr pipes and silencers. I believe the seller said they are Kaufman (not sure of spelling), I've tried finding them on-line with zero luck. Also the head was milled a few thousands. A few years ago I had a guy check out the engine sine it had never been apart for a rebuild that I knew of. All he did was port the transfer ports and a full tune/maintenance for me.
This Shee has run flawless ever since I bought it, so I'm not too bent that now it's acting up. I took all the plastics off and checked the wiring harness and everything was fine. I double checked all connections to make sure they were fully seated.
A friend suggested switching the coil wires to see what happens. I did this and it ran the same as with the original coil.
Another friend was also thinking maybe dirt inthe carbs. I'm pretty anal about keeping a clean air filter on, but anything is possible when dealing with sand.
Is this enough info for you or is there something I'm missing?