Morspeed

Whether the problems are inherent to all Zens I cannot say, but I have had a bad run thats for sure. When running sweet it is a excellent motor and I would buy another, there are just a few things I would check before starting out of the box.

The most damaging fault was when after about five or six runs (from new)she stopped dead in the water.

Could not get her to turn over at all, thought I had a seized engine on my hands, stripped it down and found a very small (and squashed) grub screw jammed between bottom of piston and cylinder wall. The screw was the one that secures the throttle butterfly to the throttle shaft- it had clearly worked itself loose and been sucked down the intake port, fitted a new screw (with threadlock) and machined the damaged internals to get it running again.

However, way before any of this I was having trouble getting the engine to run at all and after alot of head scratching found the two bolts that secure the venturi and carb to insulator block are about 1/8" too long and jam into cylinder head when tightening meaning the carb does not secure firmly onto head therefore allowing for a very small air leak.

And then after all this (and replacing the Cyl head gasket) a small leak became apparant between head and crankcase- not much but enough to allow loss of crankcase pressure and fuel/oil mix to escape.

On closer inspection discovered that the crankcase/ head join surface was not a perfect machined surface on the exhaust side (right where the two halves of crankcase join)- I had noted this from new but did not think much of it as it did not seem to present a problem. This was allowing for the leak and requires a tiny smear of gasket cement to remedy.

As I said , still like the motor- just would run thru this checklist before giving it the message for the first time.