Recent content by kevbo

Prop open the engine cowl and see if anything changes. What’s the top speed? If needed the pump load can be lightened by bending the trailing edges up .100”. I never measured an SC nozzle. All plastic 650 units are over 82mm and metal 750 units are 76 or 80mm. Larger diameters do make more thrust.

This time do a pump swap.

Good luck finding dimensions.

Just pull the lanyard and open the throttle. The engine is dieseling but will only do it with the throttle closed.

That bearing has been unavailable forever. Once it gets rusty the shaft will be equally pitted so little is achieved by changing it. I have cleaned and greased some rusty ones and they worked fine for a long time.

The top screw adds fuel so you can adjust the mixture. A 150 main will probably be okay with the screw closed. If not then install a smaller jet and retune. Either way you must learn how to tune your carb since every engine has different needs.

With a “good” pipe power falls rapidly AND the mixture goes rich if the load is too light. Always, always, always open the top carb screw and retune whenever ANY changes are made! Wax illustrated how fine load adjustments can make a big differences. You want to set the pump load where you see a...

It’s mostly important for skis with good pipes on them. Stock SJ exhausts and single pipe triples will only gain or lose low speed acceleration. The carb tuning will change but still be easy to adjust. If it has a pipe, the pump load needs to be light enough so there is little lag in power...

It falls on deaf ears when I say it!

The ignition boxes are big pin specific. They should be marked 3735, 3738, or higher. Small pin boxes are 3728-3734. Do not use these in any high power engine, they have no retard curve. There is a one year 750zxi cdi box that is battery powered as well as most used on 800 stand ups. The stator...

A high port 750 will need a low pitched impeller. The stock 650 nozzle will also make the most thrust. Leave the engine stock, especially its head and ignition. It is very easy to melt a piston on these with an aftermarket pipe. And, as always, open the top carb screws enough to stay a little...

I’m using a solas 11-16 concord on a “limited” 650sx. It turns 6600rpm and goes 42mph. Best low speed acceleration I ever got out of 650s.

The last time I had a 650 upside down for a 750 pump swap, I put the 650 unit back in and just modified 750 impellers. The swap was looking to be a lot pain for no gain. Mainly because the 750 pump shoe doesn’t fit.

All good pipes will make the power either on or off. If you raise the popoff you will also need to use a larger pilot to have the same 1/4 throttle mixture. Your ski may be a little over propped with your high rpm pipe.

The coffmans Yamaha 650 pipe is shorter than their Kawasaki pipe in order to make any rpm with the Yamaha 650s 172 degree exhaust port. The longer Kawasaki version will rev up to 6500 rpm with a 180 degree port. The Yamaha version will rev to 6700 with the same 180 degree port. The stpck...