Dominator sludge trap plug

I have just took the sludge trap plugs out of my '59 Jubilee and they are 5/8" x 20tpi. Dont know if your will be the same but it might help as a starting point.

Previously wrote:

Hello,

My Dominator 88's engine had water in the crankcases when I dismantled it, so everything is needing done. There's a tide line of rust on the crankshaft which is cleaning off quite well, however the sludge trap wouldn't budge despite months of soaking in penetrating fluid. I have resorted to drilling it out, but need to clean the thread with the correct tap. Can anyone tell me the correct thread size? Any help gratefully received.

Thanks

James

Hello James,

Do you mean the large crankcase drain plug, which screws up into the crankcase

and has a mesh filter, held into it with a circlip?

Either that, or you have a very special (one-piece) crankshaft.

You are going to have to get a replacement plug; so once you have that it would be

better to locate a long-established engineering firm, who are more likely to have

a selection of taps with the correct profile.

Donât know where you are; but an engineering shop who specialise in vintage bikes

and/or cars are more likely to have the right equipment.

Try giving Mike Pemberton a call (Pushrod-Performance). He advertises in Roadholder.

If they donât have one, they will know who are likely to have them nearby.

It will not be worth buying the correct tap. They are pricey and it will not be one you

are going to need in your tool cabinet.

Paul

Previously wrote:

Hello,

My Dominator 88's engine had water in the crankcases when I dismantled it, so everything is needing done. There's a tide line of rust on the crankshaft which is cleaning off quite well, however the sludge trap wouldn't budge despite months of soaking in penetrating fluid. I have resorted to drilling it out, but need to clean the thread with the correct tap. Can anyone tell me the correct thread size? Any help gratefully received.

Thanks

James

Good morning

The standard 3 piece norton crankshaft has a sludge trap formed in the crankshaft cheeks and it is accessed by dismantling the crank.

I think you have removed a plug put in at the factory after the crank has been machined and not intended for removal.

Check one of the manuals for crank dismantling/assembly instructions .

I get the feeling that a few people have got the wrong end of the stick regarding this question.

The Dominator crankshafts were three-piece with the main sludge-trap being the centre section of the flywheel. However, after big mileages and/or using cheap oil you generally have to scrape the gunge out of all three chunks.

I believe that James has discoveredthe tapping on the timing side journal. This conceals theoil passageway drilling that connects theoilway from thetiming end of the crankshaft to the right-hand big-end journal. It is not meant to be removed but if drilled out can easily be retapped and a short headless bolt/threaded plug Loctited in place. There is a similar item in the timing side crankcase that helps to connect the oil pump to the return feed from the sump.

Point of interest. In both of the aforementioned it is possible to screw in the plug too far and block the oil way passage. The Norton Factory managed to do this themselves with quite a lot of the first Atlascrankshafts back in 1962. The result being a fair number of American owners carefully ran their new engines in (usually about 500 miles), only for the motor to seize shortly afterwards.

Previously wrote:

I get the feeling that a few people have got the wrong end of the stick regarding this question.

The Dominator crankshafts were three-piece with the main sludge-trap being the centre section of the flywheel. However, after big mileages and/or using cheap oil you generally have to scrape the gunge out of all three chunks.

I believe that James has discoveredthe tapping on the timing side journal. This conceals theoil passageway drilling that connects theoilway from thetiming end of the crankshaft to the right-hand big-end journal. It is not meant to be removed but if drilled out can easily be retapped and a short headless bolt/threaded plug Loctited in place. There is a similar item in the timing side crankcase that helps to connect the oil pump to the return feed from the sump.

Point of interest. In both of the aforementioned it is possible to screw in the plug too far and block the oil way passage. The Norton Factory managed to do this themselves with quite a lot of the first Atlascrankshafts back in 1962. The result being a fair number of American owners carefully ran their new engines in (usually about 500 miles), only for the motor to seize shortly afterwards.

I wonder if that isnt the plug that John Hudson advises all not to remove in his Norton engine video of some years back. "you're right again John" He certainly knew his engines!

Hello - you dozy set of guys,

You do not need to drill that plug, all you needis paraffin and an air gun to blow it through from the end of the crank where it's fed oil when its stripped down. I hope you marked all the crank for alignment - even a woman knows this fact ?? Yours Anna J Dixon

Dear James,

the tapped thread in the timing side cheek is 1/4" BSF (26tpi).

the blanking plug was used right up to the Commando engines so acquiring one shouldn't be difficult, or alternatively cut the end of a bolt off and put a slot in the end with a hachsaw.

Regard

Geoff