Engine breather

[Superarnie]

Good afternoon.
The breather component that sits on top of a cork washer and locates on a small dowel welded into the camshaft spindle, seems to be a precarious arrangement. Especially with the breather shoulder then pressing up to the inside boss of the inner timing soft alloy cover, and the breather 'tube' fitting through the hole in the inner cover with no bush of any description. Also, why only one dowel, why not two to even the pressures on rotation forces (torque). It is sandwiched in position between the inner cover and a soft cork washer and just sits over the end of the dowel. Has anyone had any issues with this whereby the breather has dislodged   ie, come off the dowel, and is there a way of minimising this from occurring.
Many thanks
Gary

[Superarnie]

Just re- read the above, I meant camshaft sprocket, not spindle!

[JulianS]

Been riding my A10 for 50 years and, given a cork of the correct thickness,  never had any problems with the standard breather arrangenent.

[KiwiGF]

Good afternoon.
The breather component that sits on top of a cork washer and locates on a small dowel welded into the camshaft spindle, seems to be a precarious arrangement. Especially with the breather shoulder then pressing up to the inside boss of the inner timing soft alloy cover, and the breather 'tube' fitting through the hole in the inner cover with no bush of any description. Also, why only one dowel, why not two to even the pressures on rotation forces (torque). It is sandwiched in position between the inner cover and a soft cork washer and just sits over the end of the dowel. Has anyone had any issues with this whereby the breather has dislodged   ie, come off the dowel, and is there a way of minimising this from occurring.
Many thanks
Gary

Breather system on mine works fine, but I did have to make up a longer dowel as mine has the max cork thickness, and yes there was evidence of the dowel having slipped out of engagement in the past, but its not common, I guess because the force on it is very low.

[Superarnie]

Yep, thanks for your inputs. The reason I posted this is because I have just finished a full restoration on my 1960 Spitfire Scrambler. It started up after the 4th kick and ran beautifully, However when I put my strobe on to check the timing advance (Thorspark elec. Ign fitted) I noticed it wasn't advancing as the revs increased. In order to diagnose the problem I took the timing cover off to look at the auto advance unit to find the cork washer on the camshaft sprocket had disintegrated, the breather had sheered the dowel and was lodged and jammed at an angle in the inner cover hole, ruining the breather itself and the inner casing boss, and of course the dowel in the sprocket. Fortunately it doesn't look like there is any damage to the valves or anything else (fingers crossed). So I have ordered replacent parts which should arrive over the next week. It made me look at the breather arrangement and I have concluded that it's poorly designed. Anyway....I think I had too thick a cork gasket on which left little of the dowel for the breather to locate on and as the engine has turned it has slipped off the dowel and in the process has sheered the dowel and then jammed itself at an angle in the inner case. I suspect in my keenness the remove any push/pull clearance, I went too thick on the cork washer. I was interested to hear what others have experienced.

[muskrat]

G'day Gary.
Ouch! The cork has two jobs. 1 to seal the breather and 2 to take out any end float of the cam. The valve timing would not have been affected.
Select a cork that gives about 10 thou" crush when putting the inner cover on. Too much crush parts will wear, not enough breather won't seal and cam will have end float.
Cheers

[Superarnie]

Thanks Muskrat,
I think by putting too thick a cork washer on, with the best intension to seal and eliminate end float, it has strongly forced the shoulder of the breather up against the boss of the inner timing case and caused them to jam together. I won't make that mistake again!

[chaterlea25]

Hi Guys,
It is wrong to think that the cam end float is set by the cork washer !
The cam position is governed by the gear being done up tightly to the cam shoulder and the thickness of the
cam bush flanges..
As Musky wrote, fitting a cork that provides a little crush is the way to go,
Sand down a thicker washer if one in the kit does not suit,
If the cork washer is a touch loose you can add a gasket paper washer inside cork one.  New cork washers settle after a while and lose the "seal" adding the gasket paper washer will usually fix this.
I judge the "fit" by firstly try and rock the breather top hat back and forwards with your fingers, if you can its too loose
I aim for being able to rock the top hat easily with some small pliers
If the dowel is a bit short you can knock it outwards a touch otherwise make a new one

John

[muskrat]

G'day John.
It is wrong to think that the cam end float is set by the cork washer !
Yes you are right but I've never seen one that doesn't have end float to some degree. The small amount of crush of the cork eliminates this.
If there is more than 1mm end float of the cam before the cork and inner cover are offered up I'd say it's time for new cam bushes.
Cheers