crank sludge

Ian James · Dec 22, 2019

How do I clean the sludge trap.

TheFrib · Dec 22, 2019

You have to unbolt the connecting rod journals from the flywheel. Obviously the sludge is inside. It is fed from the timing side. Clean and reassemble. New nuts and bolts should be used. I am in the process of doing the same to a 71 commando. So far I have only got the bearings off the ends of the crank. Going to use superblends.

texasSlick · Dec 22, 2019

Is there any solvent one could use to avoid breaking apart the crank??

I would think a long hot soak in some solution would loosen up the gunk ..... but what?

Slick

Blewdy Yaink · Dec 22, 2019

TheFrib said:
You have to unbolt the connecting rod journals from the flywheel. Obviously the sludge is inside. It is fed from the timing side. Clean and reassemble. New nuts and bolts should be used. I am in the process of doing the same to a 71 commando. So far I have only got the bearings off the ends of the crank. Going to use superblends.

Is you have time and access to a good machine shop, while you have it apart, have the matching faces of the two crank throw halves surfaced 100% flat and perpendicular to the axis of the bearing boss. Then, true the fixing areas to match those faces (blue and scrape like a bearing) before you reassemble, as Mr. Frib says. Dynamic balancing isn't really necessary but can't hurt.

Triton Thrasher · Dec 23, 2019

texasSlick said:
Is there any solvent one could use to avoid breaking apart the crank??

I would think a long hot soak in some solution would loosen up the gunk ..... but what?

Slick

I would expect organic solvents to be ineffective.
Sodium hydroxide (caustic soda) will attack the sludge. I have no idea how long that would take or what else in there it might attack, because everyone does the obvious and dismantles the crank to hack the stuff out.

ashman · Dec 23, 2019

Owning my Norton since new and rebuilt motor 2x in all the years I have owned it and I have never done the sludge in the crank but just over 7 years ago when I had to replace a cracked crank case I decided to do the crank to clean the sludge out after pulling the crank apart I was surprise to find very little sludge in the crank and was not enough to worry about splitting my balanced crank, so doing regular oil changes has helped with no build up of sludge.

Ashley

marinatlas · Dec 23, 2019

ashman said:
Owning my Norton since new and rebuilt motor 2x in all the years I have owned it and I have never done the sludge in the crank but just over 7 years ago when I had to replace a cracked crank case I decided to do the crank to clean the sludge out after pulling the crank apart I was surprise to find very little sludge in the crank and was not enough to worry about splitting my balanced crank, so doing regular oil changes has helped with no build up of sludge.

Ashley

Sure an oil filter will help a lot .

baz · Dec 23, 2019

Personally I'd always split the crank and clean it
I couldn't have the thought in the back of my mind that I hadn't cleaned every last bit out
Would you really trust a solvent?

batrider · Dec 23, 2019

I helped a friend with his '71 back in the late '70s and the sludge trap was packed solid with metal paste. Don't assume it's clean.

Bernhard · Dec 23, 2019

The crank should only be cleaned out around every 100, 000 miles unless you have NOT done regular oil changes or had an engine blow up with bits everywhere.

robs ss · Dec 23, 2019

Ian James said:
How do I clean the sludge trap.

As no-one has mentioned it yet, if you do disassemble the crankshaft:
1. Mark or engrave which side goes where - mistakes have been made.
2. The "keeper plates" are important. Not to keep the nuts from turning but to keep the dowels in.
3. Use loctite (at least blue - I use red) plus centre punch after torquing to ensure everything stays tight.
4. If you have the crankshaft out I believe it is a very good idea to have it professionally dynamically balanced - in Aus only about $200.
Good luck!

kommando · Dec 23, 2019

Even if there was a magical chemical that would loosen and remove the concrete, as you cannot inspect it to check it is clear it has to come apart anyway. You do not want to clear 90% of it and leave 10% of loose debris in there to come out the big ends when its started up.

maylar · Dec 23, 2019

I cleaned mine at about 30,000 miles and found nothing. Just a bit of oil.

Blewdy Yaink · Dec 23, 2019

(As much as I may regret asking this question

), what oil do you use, Dave?

maylar · Dec 23, 2019

Blewdy Yaink said:
(As much as I may regret asking this question ), what oil do you use, Dave?

Was GTX 20/50 per the manual for a long time, now VR1.

Bernhard · Dec 23, 2019

To quote from elsewhere on another website " I use GTX 20/50 in my shovel"
That's it, you need a new oil!

Torontonian · Dec 23, 2019

Cleaned out my 70 trap whilst apart to fit Superblends and there was a thick hard layer of sludge in there to scrape out. Glad I did it. Cleaned out my 72 trap to do the same and found next to no gew at all. So you never know.

dave M · Dec 23, 2019

Rob SS is spot on about marking the crank cheeks and flywheel left and right. The flywheel is symmetrical except in relation to its balancing holes and if you reassemble the wrong way you will get a nasty surprise when you run the bike.

MexicoMike · Dec 24, 2019

Can't think why cleaning a sludge trap would be anything to consider unless you are disassembling the engine/crank for some other specific purpose.

jseng1 · Dec 24, 2019

The sludge packs hard into the outside diameter of the sludge trap and doesn't move. So it doesn't actually hurt any thing unless the crank has been stored dry for years. When that happens the sludge can dry out and turn to powder. The powder will mix with the oil and embed itself in the soft shell bearings as small black specs.

So always clean out an old stored and dried out crank.

A high mileage running motor can fill the sludge trap up to 1/2 full and no more. Once it fills up to the oil holes it will continue to bleed out the oil holes and won't add any more sludge - not a problem unless the oil is drained and the motor is stored long enough for the crank to dry out.

crank sludge

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