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General => Douglas Motorcycles - General Discussion => Topic started by: Aero on 14 May 2019 at 12:25

Title: Tappet guide oil slot upwards or downwards?
Post by: Aero on 14 May 2019 at 12:25
Common sense would suggest the oil slot in the tappet guides should face upwards, but I have seen them facing downwards in quite a few pics on here.
Can anyone give me a definite on this please as I'm assembling my engine this week?
Title: Re: Tappet guide oil slot upwards or downwards?
Post by: Doug on 14 May 2019 at 21:11
The slots I think you are referring to are to place a screwdriver or a drift against to knock the tappet guide free of its taper. It does not break through to the bore and so is not a oiling feature. So they should face the timing cover, except the one at the lower rear. That one has to face downward at an angle due to being blocked by the supporting casting. Again, align so as to afford the best purchase with a drift for knowing out.

Oops, just noticed in your pictures you have an additional slot. Not sure if that is original, or a modification. Presumably it should go up to introduce oil. Problem is the same lower rear tappet guide mentioned before is blocked by the casting for the slot to be any use. There should be several small holes between the timing chest that the tappet chests. A larger hole part way up to allow oil mist into the tappet chest to oil the valve stems. Then a smaller hole to drain oil back from the tappet chest to he timing chest. So if it has those holes, no reason to have the slot in the tappet guided facing downward to drain out excess oil. Unless they found too much oil was going into the tappet chests...

-Doug
Title: Re: Tappet guide oil slot upwards or downwards?
Post by: Doug on 14 May 2019 at 22:14
Correction; my '36 Aero has the oil slots too. They are pointed down, and not visible in the photo I have on the computer. I did not recall them, but I started to get a nagging feeling of doubt and whipped the timing cover off and had a grope around in the timing chest. Presumably I positioned them downward to drain as that is the only consistently open orientation at all four tappet guide locations.

-Doug
Title: Re: Tappet guide oil slot upwards or downwards?
Post by: Aero on 16 May 2019 at 19:23
Doug,
thankyou for taking the time to check yours.
I have seen 2 pics on this forum so far, one (Erics) had the visible oil slots up & the other (yours) had them facing down.
I can now see by witness marks where the old hold down clamps had been fitted on my engine that originally both the rear guides oil slots faced down, whereas both the front faced up! So, just like the generator drive, we have 3 variations!