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by Mal Marsden - 06/16/22 7:00 pm
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Allan G, Chip H, gavin eisler, kommando
Total Likes: 10
Original Post (Thread Starter)
by Bustednukel
Started to "try" to remove the sludge trap on a basket A-65 a few weeks back. Realized its a little beast and scratched around for my drag link socket. Once found, the drag link socket was a little too big, but nothing a carbide cutter could not correct. Now find the little carbide cutter!!!

Got side tracked by the cold weather, chopping wood, grandson's car problems, daughter's car problems, my truck problems, caught covid and quarantined. More my truck problems.

Now all caught up mostly and thought about that little beast still stuck in my A-65 crank. Why is that sludge trap even there? One answer might be that modern oil filtering techniques had not yet been adopted. Which got me wondering where the sludge in the trap is coming from? Oh, its scavenged from the bottom of the crankcase by the oil pump back to the oil tank where it passes right through the oil screen at the bottom of the OIF and sucked back around by the oil pump to the crank and gets caught eventually by centrifugal filtering at the sludge trap. Oh!

So, if there was a proper oil filtration process, the sludge trap would be unnecessary. The sludge in the crank passage would exist elsewhere not at the most inviolate spot.

I need a proper oil filtration process. So far I have searched BritBike and found the words "Charlie type oil filter", "Motao filter". Just got to get it together.
Liked Replies
by BSA_WM20
The "sludge trap" is a short name for a full flow centrifugal oil filter.
It take out every particale of debris in the oil that is heavier than the oil regardless of its size .
They are very good & very efficient , till they get fully pluged up.
And the sludge is timy wear particles and carbon from combustion.
2 members like this
by triton thrasher
triton thrasher
Carbon black is denser than oil and finer than the pores in a full flow paper filter.

Simple as that.
1 member likes this
by koncretekid
Originally Posted by DMadigan
The B25 single with its plain rod bearing does have a sludge trap in the crank journal. The B44 and B50 with their roller bearing rods do not.

B44s and B50s do have sludge traps.

[Linked Image from]

1 member likes this
by Gordo in Comox
Gordo in Comox
If I read the charts correctly a 1/4W or 5/16 BSF socket would fit a 0.525" bolt head. I do not have a crank handy to measure to see what size I get.

1 member likes this
by Irish Swede
Irish Swede
Hey, Bustednuk,

Better check (and maybe replace) those wheel studs. There are specific torque ratings for wheel studs, and 300 ft. pounds isn't it.

Some "cowboy mechanic" over-torqued those on one of my trucks sometime in it's former life, and the first time I did a tire rotation, several of them broke.
I decided to punch all of them out and pull in new ones.

The last thing I wanted was to have more of them break if I had to change a tire alongside the road.
1 member likes this
by John Healy
John Healy
Applying heat to the side of the flywheel adjacent to the threaded bolt hole IS A MUST. These bolts are supposed to be installed using Red Loctite.

They are hardened steel and quite brittle. You can break them. Especially if you don't release the Loctite with heat (and the surfaces were clean when assembled and it worked like it is supposed to). Old Loctite wasn't tollerant of oil covered surfaces) THEY DO BREAK!

Breaking them is a confounded nuisance. You will not be able to easily remove broken part from the crankshaft. It will also be difficult, if not imposible, to remove the flywheel from the crankshaft to make the removal easier. Best way is to have it removed by EDM.

Where does all of the sludge come from? Carbon created by combustion by-passing the rings. If your piston and head is covered with carbon chances are your sludge tube contains a lot of this carbon also. The carbon is so small that oil filters do little to keep it out of the sludge tube. Oil filters are good, but routine oil changes are a must in one of these engines.
1 member likes this
by NickL
As said above, warm the crank centre with a gas torch if they are solid in there.
You must get the tube out to clean the cavity properly. The job is not a 5 minute one.
1 member likes this
by Allan G
Allan G
Originally Posted by gavin eisler
The 71 WSM has 45 lb.ft. as the torque on the flywheel bolts, 0.38 ( 3/8) B.S.C. 26 tpi.
Not 25 lb.ft., not 5/16".

I used 5/16" as an example (intentionally pointing out that you don't want to use the power of Thor to undo the bolts), I didn't have a set of bolts or a manual to hand for propper sizes and torque.

Originally Posted by gavin eisler
You guys are lucky I keep the WSM by the PC.

It does help a lot. I would usually refer to the WSM etc collection on my laptop, however the wifi card has failed and I haven't had the time to fix it.

Originally Posted by gavin eisler
A norton type cartridge filter can be mounted using a U clamp to the lower frame spine section, off set to the TS so it clears the back tyre, plumb it into the return line. As well as doing a fine job keeping the oil clean it also adds useful oil volume, never a bad thing.

My version of this: its still in prototype status, I don't really like a 3" U clamp going around the frame, but will fabricate a "nicer" bracket and utilise the rear footrest mount as additional support. Though so far it seems to hold up ok.

[Linked Image][Linked Image]
Attached Images
1 member likes this
by DMadigan
You mean something like this?
[Linked Image from]
If you do not want to make the 90 degree bends with the hoses the bracket could be extended and rotate the filter 90 degrees similar to your steel bar and U-clamp.
1 member likes this
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