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I did the case/carb change leaving all else the same. The 62T case with dual 44s made the pipe hit a little harder compared to the 61X case, top speed was the same. The cylinder was a ported 701. Port work, a good pipe, and a low pitched prop made most of the thrust increase.

One of our local riders battled this condition recently. He found the stock flame arrestors were a bit restrictive acting like a choke. Switching to open F/As and retuning ultimately cured the problem. Without making two changes at once, try closing the top screws until the right side bog...

That pipe/prop should turn 6900rpm with a bored nozzle, well over any 6M6 cdi that I have tested. Look in the tech section and decide if you are up to the task. I replace the 91ohm resistor with a 75 and seal it up. It gets the limit out of the way.

Old skis are generally in very poor condition, so this is the most important consideration from an ownership perspective. The people you ride with and type of riding that is most popular will dictate your enjoyment of old Kawasakis. At one time the Superjet was considered a turd compared to a...

There is an almost direct trade-off between response and power as the ports are raised, all else equal. Small engines burning pump gas need low ports for any throttle response. Larger engines, especially with high compression and programable ignitions can have good response with very high ports...

Anyone try a ZXI gimbal and bucket?

I have a new Kawasaki 21121-3711 coil that has 18" and 23" leads, I think it fits a 750XZI. The OEM Superjet coil I bought has leads approx 6" longer. Try gaping the plugs down to .025 to reduce arching.

Use race gas to keep your pistons free of holes.

I suspect that you have too much load, try a flatter prop, you will probably gain a lot of thrust. Dont get a larger pump unless your hull already has a 155 inlet.

It wont be over loaded because of the 650s low port timing. A stock 650 will only rev to the low 6000 rpm range, that is where a 9-15 will load it. A good 771 with a pipe will turn the same prop around 1200 rpm higher and make 40% more thrust.

For the money, do what he said.

Maybe so, but those are only marketing terms without basic technical data to go along. Would this cylinder have so many foaming at the mouth if it was smaller and more expensive than what is already available?

All it ever needed to be was big and cheap, nobody really cares about anything else.

I never found Keihin carbs to be very sensitive to popoff changes beyond 1/4 throttle, I could clip the spring a lot on a 38 installed on a 650 without penalty. I dont recommend this very much, but it can be done. The top screw is more sensitive and covers more like 30 points of main jet sizes...

The bottom mixture screw is for idle only, 1/4 throttle is pulling through the pilot. A 75 pilot should be big enough but on the lean side. You may clip one coil off the spring or install a 78 to make it richer. Did you install the thin plastic check valve correctly? If not the carb will run...

I bet Dave recommends his 10/16 a lot since he doesnt have to bend them to 9/15. You can bore the nozzle and repitch easily if that 62T cyl is still a little sluggish getting to the pipe.

The aspect that worries me is 94mm bore. I fear the minimum octane requirement will be high unless power is reduced to levels of a smaller bore cylinder.

Detonation has a way of ruining everything, which leads me to my next questions. What is the minimum octane for extended full throttle runs? Is this even possible with peak power mixture?

Teflon pipe dope will do a good job of preventing corrosion in the threads, especially on the water injection screws. Most of them are stuck in used pipes.