Rebuild & Sludge trap advice

Hi, am rebuilding a 1970 750 and am getting the head rebuilt with new valves, guides, etc, plus a rebore to +20 (they were on +10 with the old slotted pistons).
Whilst the top end is off, I've thought about the bottom end and the sludge trap. The cam seems in really good condition if that is anything to go by. It's not had an oil filter fitted either, but will have.
The bike has done about 300 miles in the last 10+ years!
What do you guys think- should I dive in and do the whole job? Or can I save it for later?
This was going to be a 'quick' rebuild, but I guess I should have known better!
Thanks a lot

Doing it will give you piece of mind for the next 40 years + its not a difficult task and a few hrs of work (esp if superblends are installed - which you can checkup on it you aren't sure)

There is a motto in the old Brit Iron bunch, Clean The Sludge Trap! It will be a long time again before as easy to get to and be done with it. Also we'd all like to know what amounts found in there to judge our own resistance to Clean the ....
Main item for me getting the fasteners back on tight enough to stay tight and locktie ain't that locking at the heat in there.

hobot said:

Main item for me getting the fasteners back on tight enough to stay tight and locktie ain't that locking at the heat in there.

Click to expand...

Same here. I always clean out the crank when I am in the bottom end. I go back with new bolts and locktite but I am never really sure. The worst offending crank slug traps I have seen have been Triumphs. I have never seen a Norton crank packed up with sludge like I have a Triumph. Maybe the filter does help even if it is on the wrong side of the engine. I have seen several Triumph 650s tie up the left rod big end for lack of oil but never a Norton.

I have seen a Norton sludge trap packed solid with metal paste but have never had mine apart. If you have the time and don't mind the work do it.

13,000 miles, no oil filter.



Dave
69S

I had to make this decision a few weeks ago and I am glad i did split the case. Even though I had good oil psi one rod berg was bad and the bolts that hold the crank together were only hand tight! Sludge trap was clean. Had less than 9K original miles on that bike.

I'm not sorry at all that I broke mine apart. Now I know what I have.

Dave
69S

Above is 1st report ever of a packed trap to block oil flow I ever heard of in a Commando. I take good note of this but must of been a totally clapped out engine with derelict desperate poor owner running it into the dirt w/o oil attention. Even though I suggest and recommend looking in after seeing how fast it can accumulate and yet not block nothing, in my own Commandox I'd never bother to open crank again until rod shells sieze and blow up, so much so now I understand the dynamic involved, that essential self clearing unless some big size swarf block the oil holes, its like my spring branch creek that gravel accumulates till a good bit of rain flow occurs then washes it all right out into the small river size main creek., so what I've seen it that the flow by pump pressure and crank sling will just blast through normal sludge particles settling in the flow path to the rod shells and settle out in the valley of trap until streamlined like D shaped exhaust ports. Any onw who claims an oil filter prevented their sluge build up up has not examine what the sludge is composed of like me to microscope level, which showed its the stuff that blow though a filter like air through a window screen, so if not hardly any sludge then a very low use engine or a very attentive building and oil change frequency to point of wasteful environment issue to deal with. After opening a crank up to say ya have, next time just check fasteners and run with it for decades like my bud Wes.

I have noticed on the Norton crankshafts that when they drill the oil holes on the rod journals that sometimes there is a bit of a burr left around the hole on the inside. I have been taking a small spherical stone on a mandrel and cleaning that all up nicely then polishing it. I am sure it helps the oil get out of the crank to the rod bearings a bit and may even remove a bit of a stress riser.

Just a little something extra to do while the crank is apart for cleaning etc...

I took mine apart and rather regretted it. Didn't find more than a thimble of goo and the new fasteners that I got from Norvil were poorly made and didn't fit tight in the cheek holes like they should. I used them anyway, with red Loctite but in hindsight I wish I'd never taken the crank apart.

I'm wondering if dunking in a hot tank would wash the sludge trap out?

Regardless of whether or not it needs it, if part of your Norton journey includes being able to talk to other enthusiasts and be able to talk about what's inside your crank, then you might as well get on with it. Face it, that's why a lot of us have vintage bikes. If we didn't want to work on them we would own Hondas. Oh, wait! That is a different thread!

I got the Norvil bottom end kit, and didn't have any issues with it. I guess I was lucky, he even sent me C3 bearings at his disgust. But I get leery about ordering more things from him from what I've heard. Especially the backwards numbers on the gearbox that was posted here a while ago.

Dave
69S

BS, like me I'd suspect most would much rather ride and just add fuel and oil and wipe off road dust instead of long intimate expensive internal relationships and would indeed be on a Honda if they had half the character of a well fettered Commando. Of course there are those who live for the hands on involvement but I suspect rather low numbers compared to the rest of us slackards just wanting to be happy pilots. I was surprised how tight the crank fasteners were on first removal and how loose they were even after such hi torque it broke off end wrench jaw. Commando fettering is risky business regardless of DIY or shopped out, ugh.

BS? LOL!

Hobot, have you ever owned anything you didn't take apart? Be warned there is a guy posting photos in the Sexy Parts thread that is using your avatar!


Russ

Aw shoot we are all silly fools to ride motorcycles so might as well make the most fun of it while able. I didn't have to tear into Lexus LS 400 or XJS 4.2L Jaguar or 6.9L Mercedes but did on big block jet boat and Chevy van and P!! to re-ring and repair fractured forks to weld back. I would not of attempted my big mower recovery until my sense of self worth mechanic wise was increased greatly by all the handling of Commando innards I was forced into. I enjoy seeing the old posters with impossible to survive postures with grinning females to hang on to. I would not of parted Trixie's crank shaft but for the TS cheek getting bent on a rod bolt let go. I did not find sludge enough to bother with, maybe 1/16-1/8" thick layer that just streamlined the oil path into the oil exits and stable as could be to require blade to remove. Examined by magnets and lens reveals the sludge is mostly metal dust with some hydrocarbon polymerization holding it like soft ceramic and coloring darker than the grey silver bulk of it. Non of this can be filtered out by regular hi grade filters whose only reason is to catch big stuff that could block a passage but nil protection for wear particles. This little sludge amount and so close to spin axis has nil effect on BF, the oil volume has more effect that way.

Looks like I'll be taking the crank apart then- at least I can check the mains for Superblends. As it had the old slotted-type pistons, I'm not taking anything for granted, plus it'll make it oil tight(ish).
Pistons also look like a bit of a mindfield, was going to go with the JCC/ Hepolite as the GPM's don't seem to have any advantages?

There is currently an interesting thread on crankshaft bolts. Might as well check it out.

A Norton with a spin-on filter and regular oil changes does not get any accumulation in the sludge trap.

IF you take apart some old Commando engines that have had a spin-on since new, even if the oil change was neglected, they have very little buildup in the crank and the rod shells and journals look much, much better than those out of an engine run the same mileage with no spin-on.

Some of that shit always gets out the journal oil hole, embeds in the bearing shell and scores the shell and journal up. The bearing shells out of a non-filtered engine are always full of little shiny embedded particles that turn the shell into a sort of sandpaper to turn your journal undersize.

It is economical also, as your crank and bearings will go a lot longer before they need ground etc..

So if you have a collectors item you are only riding 500-1000 miles a year and changing the oil every year, that is one thing. But if you are using a Norton for transportation and plan on getting tens of thousands of miles out of the bottom end, then you will be a lot of money ahead to get a spin-on filter on the bike.

So if you have a collectors item you are only riding 500-1000 miles a year and changing the oil every year, that is one thing. But if you are using a Norton for transportation and plan on getting tens of thousands of miles out of the bottom end, then you will be a lot of money ahead to get a spin-on filter on the bike.[/quote]


I use mine for transport....so my second commando i am building now will have a screw on filter......I may even add one to my 71 also.