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General => Douglas Motorcycles - General Discussion => Topic started by: Henrik on 03 Sep 2010 at 09:00

Title: Oilsystem Blue Chief
Post by: Henrik on 03 Sep 2010 at 09:00
Hi please advise me,
want to close the breather hole on my blue chief using a thin plate behind the bearing.
Then install a redvalve as a breather lower or where there is sufficient place.
My concern is the purpose of an existing hole, is that to maintain a certain height of oil in crankcase to splash oil on cylinders? Or is it just a hole drilled later for some obscure reason, it could have been drilled lower.
Otherwise I will put redvalve as low as possible.
Lubrication of the timing gears? it had a small homemade pipe to the scavenger pump inlet in order to keep 2 cm oil height, is that necessary?
My oilpump is still usable, but would like to replace it with one that has bigger especially scavenge capacity. Was that pump made by Douglas or used on other engines? Any good ideas?
Regards Henrik

(https://www.douglasmotorcycles.net/aa-files/images/henrik/2010/blue-chief-oil1-750.jpg)

(https://www.douglasmotorcycles.net/aa-files/images/henrik/2010/blue-chief-oil2-750.jpg)
Title: Re: Oilsystem Blue Chief
Post by: Doug on 04 Sep 2010 at 01:10
Henrick,

The purpose of the hole indicated is to set the level of oil in the timing chest, and ensure that the bottom timing gear dips into the oil. Surplus oil flows through the hole into the crankcase compartment. There, along with oil escaping from the big end bearings, in is collected by the oil pump inlet, and lead via a gallery through the timing case wall to the scavenge side of the oil pump.

You would be ill advised to block off the hole with a reed valve.

-Doug
Title: Re: Oilsystem Blue Chief
Post by: Henrik on 04 Sep 2010 at 21:18
Thanks, I will leave it then, it just looked like it was made latter.
Forgot the scavenger has suction from the crankside, will have to look again next time I come home, sorry :oops:
But I still have a problem with the damaged alu were the original breathervalve should have been.
Could try welding it and machine it back to shape, but would like to avoid it.
That's why the redvalve idea started, could instead install a external breather also the easiest thing to do.

Regards Henrik



Title: Re: Oilsystem Blue Chief
Post by: Doug on 05 Sep 2010 at 03:51
Henrick,

Where the bearing bore is damaged as well you can make a good repair by machining a steel sleeve that includes the back wall of the bearing bore. The opposite face of this can be a new surface for the disk valve to run against. Included are pictures of just such a repair on my A31 crankcase. I am not sure if the following approach can be modified to just repairing the seal face, as the problem then becomes how to adequately secure it in place.

-Doug

(https://www.douglasmotorcycles.net/aa-files/images/doug/2010/A31/A31-repair-1.jpg)

A non-original steel ring has been let into the magneto opening as well, to repair damage inflicted by a cretin with a rasp.

(https://www.douglasmotorcycles.net/aa-files/images/doug/2010/A31/A31-repair-2.jpg)
Title: Re: Oilsystem Blue Chief
Post by: Edin on 05 Sep 2010 at 06:29
Hej Henrik
I have made a similar repair on my Blue Chief (with an Aero engine) and the bike runs very well after this repair and
made two Skagen Rally without any problem.
You can contact me and we can make the repair together.
Regards Edin DK
Title: Re: Oilsystem Blue Chief
Post by: Henrik on 05 Sep 2010 at 20:01
Hi,
sorry you only have part of the story, the crank has snapped in the past and somebody has fitted it with a short DT crank.
That's part of my obsession with a redvalve plus I don't have the breather valve.
The cylinders are to narrow to each other for a DT. But has moved them 2,5mm out and the plan is the rodends will press equal down and not towards the side. Hope you will understand my English.
Thanks for the offer Edin, see you.

Regards Henrik