Oil leak dizzy stump

[DEVONMAN]

If you go EDIS, etc, it's common to cut down a dizzy to a stumpy, just to drive the oil pump. Many of these don't have anything to stop the shaft just pulling out, so no plastic thingie to the top.

But surely in the case of a stumpy the top of the shaft is covered / enclosed to prevent ingress of dirt etc and therefore oil would not be able to exit the top. Agreed no need for any plastic thingy in those cases. I'm 100% sure (seen it several times) that a standard dizzy has a plastic device which acts as a thrust washer and a seal. This is set into the housing just below the spinning weight support.

[DaveEFI]

I'm not sure. The shaft gets pushed upwards by the thrust on the gears, so dunno that plastic washer does in practice. Not a lot is my guess. My stumpy does have a cover, but didn't set out to make it oil tight, so no gasket or whatever.

But when an RV8 leaks from odd places, it's almost certainly down to crankcase pressure. It should run under a slight negative pressure.

[DEVONMAN]

Personally I don't much like the idea that the dizzy shaft can drop and take up all the slack in the toggle to oil pump spigot joint when at rest and then move up under the influence of the cog thrust. It may well work ok but iffy engineering in my opinion. I'd much prefer to see some form of counter thrust washer at the top end of the shaft to positively keep the gear at the correct level relative to the cam gear..

[DaveEFI]

See your point - but any RV8 dizzy I've come across has always had at least some end float. Which will be taken up when the engine runs.

[Pitschi]

have not opened the "old" dizzy yet but the new one was my solution. The "old" dizzy was brand new just layed on the shelf for a few years.