[Cmarch]

Need some help...
My daughter was riding her pwc and popped a hole in the upper crank case behind the starter. Appears to be a regular problem since I see many have been repaired in the same area. I pulled the motor and when I removed the cylinder I noticed the power valve was gone. I checked the front cylinder and that one is gone too.
since the is no engine damage, does the engine really need the power valves?
Looking forward to comments.
Thanks

 

[Dave in DE]

Yes, the valves are needed.
One valve blew out the exhaust without getting caught and causing damage. The other probably caught and created the failure causing your hole. Not uncommon. The remains of the valves are probably in your exhaust water lock.
The one valve may have blown out awhile ago without damage. The second has been carrying the front cyl till it let loose and granaded motor. If this is the case it still wouldn't have been running at peak performance. But would have been able to make full rpm ranges. But I suspect they both failed about the same time.

You should be able to find good crankcases on ebay. Or have yours welded.

The vales change the exhaust port timing throughout the rpm range. By doing so it allows the motor to carry a longer flater power curve. A 2 strokes power curve and output is dependent upon placement and size of all the given ports. Without the valves to change the shape/size of the exhaust port you'll have very poor low rpm performance and may not reach higher rpm ranges.