front fork spring question

noob thing here - i'm wanting to change out the fork oil in my 74 Mk2. when I removed the large top bolt, I was under the assumption the spring assembly came up with the top bolt. no go here - the spring assembly remained in the fork tube. question - what holds in the spring assembly in place? can I just pull up on the spring to remove it? I drained approximately 4.5+ ounces of oil from the right fork tube - the oil had the consistency of 30-40 weight oil - a wee bit on dirty side, but no goo or sludge. can't see how I can add in fresh oil with the spring assembly in place. with the top bolt out, if I put a block of wood under the front wheel, would that push up on the spring assembly? don't want to get into the rebuild thing at this point, just a maintenance & service thing. no experience, and I COULD USE SOME HELP.


BTW, only doing one side at a time, and the frame supported under the front iso mount. TIA....

joe czech said:

i'm wanting to change out the fork oil in my 74 Mk2. when I removed the large top bolt, I was under the assumption the spring assembly came up with the top bolt. no go here - the spring assembly remained in the fork tube. question - what holds in the spring assembly in place? can I just pull up on the spring to remove it?

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The damper rod should have been attached to the top bolt so the spring normally comes up with the bolt.
The cap bolt, nut and spacer can then removed to release the spring from the damper assembly.
Edit: Once released, unless prevented from doing so, the damper rod then promptly drops down into the fork where it has to be fished out so secure it (piece of wire etc.) before it drops.

L.A.B. said:

The damper rod should have been attached to the top bolt so the spring normally comes up with the bolt.
The cap bolt, nut and spacer can then removed to release the spring from the damper assembly.
Edit: Once released, unless prevented from doing so, the damper rod then promptly drops down into the fork where it has to be fished out so secure it (piece of wire etc.) before it drops.

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there lies the problem - the damper rod with the bushing and nut that secures the spring - that assembly remains in the fork tube, and not attached to the top fork bolt - thus my question. can I just pull up on the whole damper rod/spring assembly, or will I be opening a can of worms? what holds the damper rod/spring in place at the other end? if the damper rod is supposed to be attached to the top bolt and it's supposed to comes up, it seems i should be able to just pull up on the damper rod and spring assembly. or, as maylar said, do I just add oil slowly with the spring/damper rod assembly in place? I just want to add oil at this point - what's the best approach?

joe czech said:

there lies the problem - the damper rod with the bushing and nut that secures the spring - that assembly remains in the fork tube, and not attached to the top fork bolt - thus my question.
can I just pull up on the whole damper rod/spring assembly,

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If the nut below the cap bolt is still attached to the damper rod then the spring should have come up out of the fork but just not attached to the cap bolt?

If the nut has become detached from the rod and the rod has dropped as I mentioned the spring should therefore just pull out? If the damper rod wasn't attached to the cap and has dropped then the damper in that leg would not have been working.

Re, “a wee bit on dirty side, but no goo or sludge.” - Oh yes there is, it’s all on the bottom of the fork leg!!!!

Remove nut and bushing, damper rod falls down into spring, remove spring. Fill with 5oz of selected fluid. Replace spring, fish out damper rod with magnetic or claw pick up tool.
Reinstall bushing and nut. Reinstall top cap.
Done.

The damper assembly is held in place with lower bolt above the axle. #18 on the Exploded Andover Norton site.

L.A.B. said:

If the nut below the cap bolt is still attached to the damper rod then the spring should have come up out of the fork but just not attached to the cap bolt?

If the nut has become detached from the rod and the rod has dropped as I mentioned the spring should therefore just pull out? If the damper rod wasn't attached to the cap and has dropped then the damper in that leg would not have been working.

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Ok LAB, we're getting close here to answering my question. forget the spring - i know it's held captive by the damper rod nut - the nut is still attached to the damper rod, so the question, can I pull on the damper rod to lift assembly up slightly from the fork tube? seems to me, if it supposed to come out with the top fork bolt, there's nothing holding it in place on the other end - correct?

The damper rod slides up but is retained in the damper body by the cap on top of the damper body and the valve bolted onto the damper rod below that cap. The damper body is retained at the bottom of the fork lower by a cap screw accessible by a hole normally covered by the axle.

MichaelB said:

Remove nut and bushing, damper rod falls down into spring, remove spring. Fill with 5oz of selected fluid. Replace spring, fish out damper rod with magnetic or claw pick up tool.
Reinstall bushing and nut. Reinstall top cap.
Done.

The damper assembly is held in place with lower bolt above the axle. #18 on the Exploded Andover Norton site.

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got it, but according to the diagram, its the damper tube and not the rod that is held in place by (#18) lower bolt. it seems the damper rod slides freely in and out of the damper tube - correct? in addition to the oil, I would like to re-attach the damper rod to the top fork bolt and install everything as designed - or, am I over thinking what needs to be done here?

kommando said:

The damper rod slides up but is retained in the damper body by the cap on top of the damper body and the valve bolted onto the damper rod below that cap. The damper body is retained at the bottom of the fork lower by a cap screw accessible by a hole normally covered by the axle.

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man, I'm having a tough time visualizing all this....

Correct.

Kommando is referring to the parts connected directly to the bottom of the damper rod: items 85,86,87,88,89 below. These prevent the damper rod being withdrawn from the damper tube...

joe czech said:

man, I'm having a tough time visualizing all this....

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http://www.classicbike.biz/Norton/Repair/70up_Commando/70upCommando.pdf
Forks, Section G.

Bernhard said:

Re, “a wee bit on dirty side, but no goo or sludge.” - Oh yes there is, it’s all on the bottom of the fork leg!!!!

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The voice of experience. What follows is my speculation since I'm interested in cleaning it up myself and replacing. So, you pull out the spring assembly with the cap nut. You can then use your favorite solvent to clean that spring and rod. Ok. But how do you then get the sludge out of the bottom of the fork tube (very necessary, or at least a good thing, to do I'm imagining). The question is how then do you get the fork tubes off to clean them? Since it's closed on the bottom with only the tiny drain screw down there, with some long version of a bottle brush of your own making? A long, straight, stiff wire twisted on the end to hold a cloth (non-shredding) maybe? Or is that all wretched excess?

The only hope you have of getting the sliders really clean is complete disassembly - not difficult . While apart you can assess the condition of the seals , bushings etc. When sliders are off plug damper body bolt hole and replace drain screw and fill with solvent of your choice - soak a day , drain , scrub with brush , repeat , etc.
While I have not viewed it , Norton Owners Club in UK offers a video for forks by Mick Hemmings .
You can refill the fork oil with the springs in situ but you must pour VERY slowly and it takes forever . Better done with springs out.

The solvent should thin your goop to where it drains much faster than the oil. The only fast way to clean these things with 100% accuracy is to bite the boolit and take them down. Other than that you're left with repetitive flushes as I see it. Perhaps someone shall come along with a plan I'm not privy to, but if I've got to jack with a damn front end I'm going to go ahead and do it just once..... and do seals also whether they leaked or not rather than chance I nicked one in the process.

I see someone has already chimed.

OK, I "think" I got this figured out. if I lift up or compress the fork tube, with the top fork bolt out, the damper rod, with spring naturally comes up. this will allowed me to clean up the threads so I can re-attach the top bolt and the damper rod as designed. I can use a couple wrenches to "lock" the top bolt and damper rod together for reassembly. from the service manual, it indicates as maylar stated, SLOWLY add oil with the spring in place. as for the sludge - not worried at this point. if there is as some think, it didn't impact the flow rate while draining. to be honest, what I took out sort of looked like slightly used motor oil - didn't see any chunks of anything suspended in the oil, so at this point, it's good to go, and i'm good to go. right now, i'm thinking of just adding 5 oz of 10W30, reassembly, and putting this puppy to bed -

part of the problem here is I don't have the experience to correctly pose the question. anyway, thanks for all the input and replies.

Is there a good reference somewhere about disassembly/reassembly of the forks? The workshop manual is rather sparse on that. Like, if you wanted to replace bushings and seals do you need to remove the stanchions? Any YouTube worth while watching?

Richard Tool said:

The only hope you have of getting the sliders really clean is complete disassembly - not difficult . While apart you can assess the condition of the seals , bushings etc. When sliders are off plug damper body bolt hole and replace drain screw and fill with solvent of your choice - soak a day , drain , scrub with brush , repeat , etc.
While I have not viewed it , Norton Owners Club in UK offers a video for forks by Mick Hemmings .
You can refill the fork oil with the springs in situ but you must pour VERY slowly and it takes forever . Better done with springs out.

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I'm going to view the video by Mick Hemmings. But there is one aspect I can help with, refilling the forks. Before I say about that, I did notice when I drained the left side by removing the drain screw, it dripped out. Very slowly. Drip by drop. The right fork leg oil came out in a very thin slow stream. I figure the leg that drained by drops no doubt has a lot of gunk at the bottom -- a winter job for me.

Now, I only include the following because some have mentioned how slow it is to pour fork oil back in. To do it really quick only undoing the cap nut (and of course the drain screw to get the old oil out) I use an easily obtainable syringe. I include what I did here in a wretched excess of explanation. Please excuse.

To put oil back in, undo one leg cap nut. Put wheel on block of wood. Hold brake and push on bars to raise threaded portion of the cap nut till the spring and top nut on the rod are visible. Push the spring with cap nut to one side and, here's the only part that might be new, use an easily obtainable large syringe (in cc measure on the side of syringe -- find in a drug store -- has thread inside of large outer tube over a smaller nozzle you can screw stiff tube into), and, with the end of the tube threaded into the tip of the syringe, flatten the end of the tube and push the flattened tip down past the spring on the high side (remember you pushed the spring a little to one side -- toward the lower side. The forks are tilted and one side of the spring is a little "higher" than the other because of the tilt). And squirt the oil in. It won't leak (it didn't for me) and it goes in fast. Cap nut unscrewed, drain screw off (and then back on again!), oil squirted in. Total time, discounting drain time, 8 minutes or less -- big syringe = faster. And, of course the syringe with small tube on the end is reusable. I got the tube by cutting off a part of the rocker oil feed tube I replaced. About 4 inches. It was stiff and thick on the end so I shaved the outside of the tip of the tube thin with a box cutter so it would flatten and fit past the spring. Whew! It took longer to write than to do! Again, apologies for the excessive explanation. I was just trying to avoid a little extra work.

Joe Schlaberdowski said:

Before I say about that, I did notice when I drained the left side by removing the drain screw, it dripped out. Very slowly. Drip by drop.

I figure the leg that drained by drops no doubt has a lot of gunk at the bottom

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A poke with a piece of wire would probably have cleared it (or did you?) as that is where the sludge will build up.