Different way to change fork oil

Was helping a mate change fork oil on this MK3 850 and decided to do it a bit differently, The advantage with this method is you will have the ability to assess the condition of the "wearing bits" (alloy caps, etc) of the damper, something that is difficult to do with springs installed. He suggested posting it here to (maybe) help others.

1. Drain oil and replace screws/fibre washers
2. Firmly chock the front frame up
3. Undo the large nuts at the top of each fork leg
4. Choch the front wheel as high as you reasonably can - will expose about 6" of spring
5. Remove the large fork-top nuts from the damper rods - using a suitable spanner on the locknuts
6. Push the springs down and clamp the damper rod with small vice-grips
7. Undo and remove the locknuts and thick washers from each damper rod
8. Remove the vice-grips and allow the damper rods to drop
9. Remove and clean the springs
10. Remove large washer and push tacho, speedo aside
11. Add 150ml of fork oil (goes in quickly and easily
12. With special tool "A" (min 4" bolt stud same thread as damper rod with 2 nuts one one end - one only half on and the other as a locknut) insert down the fork tube and twist onto the end of the damper rod.
13. Pull the damper rod up - then pump up and down until you feel good damping, If not, oh dear! - you'll be up for fork/damper disassembly
14. With the damper rod all the way up, clamp small vice-grips just above the fork tube to hold it up - and put clean cloth to cover open top of fork tube
15. Make special tool "B" - about 3 feet of light cord, a knot close to one end and a thin weight (small enough to slide through the spring) tied to the other
16. Use smallest electrical tie to clamp the unweighted end of the cord to the top of the damper rod. the knot is to stop it pulling off.
17. Snip the end off the tie closely
18. Remove vice-grips and lower the damper rod again
19. Thread the weight through the spring and slide the spring down into the fork tube
20. Pull the damper rod up with the cord and snip tie off - don't drop it into the fork!
21. Holding the damper rod with needle-nose pliers, install thick washer and locknut. Tighten the locknut such that 13mm of thread is exposed above the nut

The rest of the reassembly is the same as the method in the manual - eg: lower wheel, install large washers, tacho/speedo, large fork-top nuts

I'd rather put my fingers in a vice....

concours said:

I'd rather put my fingers in a vice....

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Go right ahead...

I have to say with all the faff in taking off the fork top nuts supporting the clocks, getting the oil it etc. i found a far simpler way for Me to re introduce the oil..
Once the fork leg is drained i placed the correct amount of oil into a plastic pot & positioned this in a tray under the leg, with the aid if a suitable syringe sucked up the oil and introduced the oil back into the leg through the drain hole.
Yes when you remove the syringe you get a small amount of oil dribbling out & its a bit messy, but that is why the pot/tray is under the leg to collect it.
I did drain the oil back out & measured the quantity removed and found i was only about 10cc light so when i re-filled i added an additional 5cc to be sure
I did toy with the idea of laying the bike on its side which would have been an even better idea, but without an extra pair of hands to raise the bike or suitable soft area to lay her over i opted for the above

olympus said:

I have to say with all the faff in taking off the fork top nuts supporting the clocks, getting the oil it etc. i found a far simpler way for Me to re introduce the oil..
Once the fork leg is drained i placed the correct amount of oil into a plastic pot & positioned this in a tray under the leg, with the aid if a suitable syringe sucked up the oil and introduced the oil back into the leg through the drain hole.
Yes when you remove the syringe you get a small amount of oil dribbling out & its a bit messy, but that is why the pot/tray is under the leg to collect it.
I did drain the oil back out & measured the quantity removed and found i was only about 10cc light so when i re-filled i added an additional 5cc to be sure
I did toy with the idea of laying the bike on its side which would have been an even better idea, but without an extra pair of hands to raise the bike or suitable soft area to lay her over i opted for the above

Click to expand...

A drain plug with a tap or bleed hole would remove the need to lay the bike over. For myself I have different internals so only use 5wt oil which flows easily so the old method is not an issue.

With "Landsdowne" dampers fitted there's another way to "cheat".

I've never found it particularly difficult or time consuming to remove one leg at a time from the bike, more time is spent removing/reattaching the ancillary bits then stripping and reassembling the forks themselves.

IMO, you are either simply changing fork oil OR disassembling forks to do a complete check/cleaning. There is (again, IMO) no need to disassemble any part of the fork assembly unless there is some reason to do so - a problem you have detected or obtaining an old bike that needs general restoration. For normal fork oil changes you just need to...well...change the fork oil!

I have found that if you put the required amount of oil in a small measuring cup and put the spout against the exposed fork spring on the "uphill" side of the spring, as you tip the cup the oil will run down the spring fairly quickly. Some sort of physics involved that I don't understand but am happy to utilize. NOTE: "Fairly quickly" is a relative term in this case.

I always pull the slider off because particles seem to collect down there. A full clean hopefully extends the life of all the bits.

The "A" tool mentioned could be made in a lot of different ways. I did one from a 30mm long M6 nut, which I bored and threaded halfway to fit on the damper rod. Then a M6 rod and even a handle on it. Instead of using a vice grip, I use a piece of 1/8" steel with a 3/8" slot ( same idea as the slotted wood pieces used under the pistons when fitting the cylinder barrel ).

Onder said:

I always pull the slider off because particles seem to collect down there. A full clean hopefully extends the life of all the bits.

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Ya gotta pull the sliders / lower legs off for cleaning out the bottom legs of accumulated black sludge . That's a total front end tubes inspection , seals , oil etc. at best. No shortcuts I'm aware of. Big job.

Thanks for the comments!
One thing missing from them, though, is an easier alternative to assess the condition of the fork dampers.
It just so happens that, in this case, it fits in with the oil change.

On my modern Triumph, the proceedure for filling correct amount of oil is to measure down from edge of fork tube to top of oil level with fork fully extended, springs in etc. You do not measure oil volume, just pour it in until the level reaches the prescribed distance from top of fork. Some folks make up a straw/pipe with a syringe, with the required distance measured off on the straw/pipe, dipped in to overfilled oil, held in place such that mark on straw is at top of fork, remove excess oil without moving straw. There of course is a fancy Motion Pro tool for doing this for something like $25 USD ;-)

Can be done with forks in bike, just aim for the middle of the oil pool, not the edge where measures will be off due to lean angle of fork. Should work for our Nortons as well, no? Just take a measure from above after an accurate filling as usual...have that handy for next time.

My own method is get a medical intravenous drip set up.
Last time I was in hospital I nabbed a couple off some particularly nice nurses, and they work a treat. Fill the resovoir with how much oil required, it has markings so you can get it precise, and the other end fits into top of forks with springs still in. It has a valve and even a filter. Turn valve on once bag is hung at suitable height, go and have a beer or whatever you fancy, and when you come back or finish other job, fork leg filled, bag ready to refill for other leg and not a drip to be seen!

Re. modern Triumph. I have a 2006 Scrambler. It doesn't have drain plugs on the forks, so emptying the fork legs requires taking them out of the yokes (one at a time) and upending them over a tray to drain out. Then refill them with oil before re-assembly to the bike.

When measuring the oil level down the stanchion, it is worth tying a long string to the end of the ruler that you might be measuring the oil level with.

With the motorcycle on the centerstand and the front wheel turned full lock, say to the left, put a catch pan under the fork drain and remove the drain plug; I let the open fork drain overnight. Next day replace the drain plug with a new fiber washer; repeat on the other side. You can speed up the process, once the drain plug is removed, by gently stroking the front suspension, but the fork oil will be harder to catch and can end up all over the place.

With both forks empty and on the centerstand I support the lower frame cross brace with a scissors jack while putting a thick towel or piece of rubber mat between the jack and the frame. It is also a good idea to use a tie-down between the centerstand cross brace and the frame to insure that it doesn't retract when the fork cap nuts are free of the stanchions.

I wrap the instruments in towels and tape them up so that they will not get damaged and/or ding any near by parts. Now unscrew the for cap nuts. Slowly lower the jack until and inch or two on the springs are exposed.

I use this pump oil can which I have had for over 40 years.



With the oilier clean and empty I add about 1-2 ounces of fork oil and, holding it and the same angle I'll be filling the tubes with, pump it into a waste oil container until it stops drawing. Now I add as much of the 150 cc as it will take, but not filling to the point where it will overflow when the cap/pump is screwed back on; with this oilier it takes an additional trip back to the graduated cylinder.

I pump nice and easy, the green hose fits nicely between the spring and the tube. Once both fork tubes are filled tighten cap nuts; you're done; probably took as much time to write this post as it does to change the fork oil.

I prefer to use the Motion-Pro tool pictured below when possible.



Best.

On a full strip and clean I've refilled before the bushes go in.
It's easier with the Consentino bushes (pictured) but I have done it with the standard type too.