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A 650 wont rev very high, difficult to get much over 6500 without porting. You can replace the 90 ohm resistor with an 80 and seal it up. I did some testing and posted the results somewhere here many years ago, I forgot the details..

An un-tuned exhaust make smooth throttling but hard to get enough power out of them. The older I get the less I like riding with a good pipe.

Any flow restriction on a stock 701 pipe will result in less total power. I would not worry about it. You wont make good power without a decent pipe combined with porting and 7000+ rpm.

Keep in mind that Westcoast 550 pipe is very short.

Those Mikuni 40 dual carbs with some port work will wake it up a little with the stock pipe. It can go plenty fast with a good aftermarket pipe regardless. But ,,, the old 750 is not any kind of a freestyle ski. I like them for chasing big boat wakes because they land smooth. They are also...

That hull has a lot of lateral grip where most hulls will slide easier. It just takes some time to adjust.

The coupler needs about 60 pounds of torque. Theres enough torsional oscillation to cause a loose coupler or impeller to spin off. You can hold the shaft with soft blocks in a vise or use an old impeller.

The stock jets are 140 and 75. The main is a little small but can be tuned with the top screw. The pilot is too small and will give hesitation unless the weather and ski are really warm. I would install a 80 pilot jet and adjust the bottom screw so the engine will spool up after idling for one...

Depends on where and how the ski is stored. Getting all of the water out is all that is required if using TCW3 oil. Adding additional oil never hurts and for many probably a good idea.

Yamahas only job is to make one thing, MONEY!!! We buy whatever crap they put in front of us. Just like every other MFG.

I would use a restrictor and no flow control valve. Unless you just want something to play with.

Don't know if it was done by FPP but yes, it is a fan spray restrictor. You want just enough extra water to keep the "downstream" exhaust cool. I install a restrictor drilled to around .1 inch on my old skis..

A Kawasaki 650 pump fits with little if any hull cutting. Ues a 900XZI driveshaft and change the mid housing bearings and seals. Making a Yamaha 144 pump work right means replacing the entire pump inlet. The 144 wont work any better without doing this.

We used Solas impellers in the past, didnt seem to matter which one with larger modded engines. The stock pump is too small to work well at low speeds. I would leave the compression stock until you install a Kawasaki or Superjet pump. Kawasaki pumps are easy. The pipe will make it go faster though.

The big problem with Superjets are that all their parts add up to less than current selling prices. There is NO perfect hull for everything. Short flatwater hulls are usually (always) uncomfortable to ride for very long. Longer hulls are great for riding but won't flip. Rome wasn't built in a...

Yea but, can it make 100hp at 7000opm with a wet pipe? .

All skis have a built in dyno, if you add power they will turn more rpm and go faster. Carbs work well because the air density is similar for nearly all riders. Not many people going for high mountain sub zero rides an a jetski. I could ride my whole life and never need to adjust a carb. No...

Electronics seem to last longer at .025 or less.

Let me add, I now power tune full throttle with a tach and tune pilot/popoff just rich enough to respond well. A B8ES plug always end up dark brown with this setting.

I could never get any good information from reading a plug after a 3 second run.