New-type ridgeless magneto-side crankshaft oil seal

[James P]

It seems as if the 25-50-10 magneto-side crankshaft oil seal is no longer available in its original form; i.e. with a locating ridge which engages with the groove in the engine casing.


A set of crankshaft oil seals purchased recently, with the new-type ridgeless magneto-side seal nearest the camera.

Some research has revealed that the original seal (Kawasaki part no.92049-1302) is no longer available and I can't seem to find any reference to any correct pattern aftermarket seal (with the locating ridge) still being available either.

Since there is nothing (other than compression between the two crankcase halves) to keep the seal in position, I am wondering whether it may be displaced by vibration and/or pressure inside the left-hand crankcase. Whether this happens after a short time or a long time remains to be seen - if it is a problem at all .
Has anyone used one of these ridgeless seals? If so, for how long? Any problems?


The new-type ridgeless magneto-side seal installed.

I have devised a simple means for preventing the seal from being forced outwards, although it requires a small modification to the magneto flange. A retainer, made from (perhaps) 2mm aluminium plate would be installed between the engine casing and the magneto flange. To keep the magneto rotor and stator in the same position relative to each other, it would be necessary to machine 2mm from the inner face of the magneto flange.


Cardboard prototype of proposed seal retainer in position.

Before I modify anything, can anyone offer the benefit of their experience with the ridgeless seal?

Thanks & regards,
James

[JanBros]

I don't thinck it will be a problem. only thing I would do is fit an O-ring in the groove. It will put enough presure on the seal to prevent it from moving.

[500bernie]

Good idea Jan
Do you think there would be any benefit from superglueing the O ring to the seal?
Cheers
Bernie

[James P]

...only thing I would do is fit an O-ring in the groove...

Now there's an idea - thanks Jan! I'll incorporate that into my NEXT engine rebuild...

For the present engine, which is already assembled, I have thought of an alternative design for a bearing retainer which (hopefully) won't require any modifications. I'll let you know how it goes...

Regards,
James

[James P]

After dreaming up all sorts of schemes to address this possible problem (most of them a bit "Heath Robinson"), I think I've devised a simple solution which requires no machining.


I have inserted three M6x12 countersunk Allen socket screws into the rear of each threaded hole used by the stator retaining screws. The countersunk socket screws are Araldited in position, although no particular problem should be caused if they were to come loose. There is still enough depth remaining to accommodate the stator screws, although there is only about 1mm gap between the end of each stator screw and the corresponding countersunk socket screw.


I have arranged the flat heads of the countersunk socket screws to be 0.25mm "below" the locating spigot on the magneto flange. As a result, there is a very small gap between the oil seal and the screw head (perhaps about 0.2mm) when everything is assembled. If the oil seal begins to move, it will not move very far at all.


This picture shows the magneto flange fitted. With all three countersunk socket screws in position, the oil seal should be effectively retained.

I still like Jan's idea of using an O-ring around the oil seal and I will likely try it on the next engine build. However, I think my countersunk socket screw solution should prevent the oil seal from being forced outwards.

Regards,
James

[dirk]

=D>