Brake Bleeder for fork drain?

Everytime I have to change the oil in my forks a thought occurs to me. Is it possible to fit a brake bleeder screw in place of the drain screw? It would be a five minute job to drain and fill with fresh oil without having to open the fork nuts up top. I may be missing something obvious, and if so, please be gentle.

Fill?

A brake bleeder screw works in a simple manner due to the two step drilling in the caliper or wheel cylinder.
Duplicating that at the bottom of the fork slider would require some ingenuity.

drones76 said:

Everytime I have to change the oil in my forks a thought occurs to me. Is it possible to fit a brake bleeder screw in place of the drain screw? It would be a five minute job to drain and fill with fresh oil without having to open the fork nuts up top. I may be missing something obvious, and if so, please be gentle.

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How would you be refilling from the bleeder without cracking open top nut for letting air out as fluid presumably pushed in via syringe?

Tornado said:

How would you be refilling from the bleeder without cracking open top nut for letting air out as fluid presumably pushed in via syringe?

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I thought that, but assuming a nipple could be fitted, compressing the fork fully might be enough to suck up a pre measured amount of the fluid...
Perhaps?? (Assuming a vacuum was present)

Tornado said:

How would you be refilling from the bleeder without cracking open top nut for letting air out as fluid presumably pushed in via syringe?

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The top nut is leaky so air will leak out here anyway but over a longer period than the time to force the oil in.

kommando said:

The top nut is leaky so air will leak out here anyway but over a longer period than the time to force the oil in.

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Didnt know that. I thought the air space above oil level forms part of the pressurized system to achieve desired damping? I guess if its just very slow leaking than not a problem for damping.

Chuck_Wagon said:

A brake bleeder screw works in a simple manner due to the two step drilling in the caliper or wheel cylinder.
Duplicating that at the bottom of the fork slider would require some ingenuity.

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Look at Chuck_Wagon's picture. You would have to have an adapter that provided what the picture shows screwed into the hole in the fork leg. There is very little thickness in the fork leg at that point, only 2-3 threads and no place for a seat. I suspect that an adapter about 1" long could be made.

Next problem. The holes in bleeders are tiny - they work with thin hydraulic fluid and air. Trying to get thickened oil out and then force clean oil in would be very difficult and probably impossible without removing the top nut or at least loosening it almost all the way.

On the other hand, removing one top nut and the drain plug and then the spring will get the oil out quickly. Putting the drain plug back in and then pouring the oil in before putting the spring back in will get the oil in quickly. Then putting the top bolt in is easy too since the other side is holding the front end up. The way I deal with the damper rod is a piece of all thread with a coupler (5/16 x 24 UNF if I remember right). Unscrew the top bolt from the damper rod and screw the all thread and coupler on. The spring will slide off over the coupler and all thread.

EstuaryBoy said:

I thought that, but assuming a nipple could be fitted, compressing the fork fully might be enough to suck up a pre measured amount of the fluid...
Perhaps?? (Assuming a vacuum was present)

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Wait a minute. The bleed nipple is meant to release brake fluid not an intake. Even if you put a bleed nipple on the fork you will still need to refill at the fork cap. Not to mention the threads are different. If removing the fork drain screw is difficult because it is a straight slot screw, there are Allen head replacements.

ILLF8ED said:

Wait a minute. The bleed nipple is meant to release brake fluid not an intake. Even if you put a bleed nipple on the fork you will still need to refill at the fork cap. Not to mention the threads are different. If removing the fork drain screw is difficult because it is a straight slot screw, there are Allen head replacements.

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It was all conjecture, thinking out loud and 'what if' to what appears to be a fantasy scenario anyways, ie: filling the forks without removing the caps
(Though we all know a bleed nipple is perfectly good at passing fluid both ways if open, no?)

I failed to receive a misspent youth, I'm not an expert mechanic. But enthusiastically learning all I can, willing to ask 'stupid' questions and research this forum. Getting to grips with doing my own work on my Commando is one of my retirement projects.

So, before refreshing my fork oil recently, another 1st for me, I researched. I was dreading it.

I was amazed at how simple it was. The most difficult part was the swapping around how the front is supported x 2 forks. The bit I was really dreading, putting the new oil in, was quite easy. Just dribble it in. It's not much and only takes 5 minutes.

Edit: I'd be interested in the trick to avoid spills and splatter when you pump the forks up and down to drain the old oil!

I pulled front ends on two bikes with Roadholders last week. Both bikes less than 5k since previous change. Both showed black silt at the bottom of the slider leg. This is not unusual and I really think pulling the sliders off and cleaning everything is the way to go.

ILLF8ED said:

Wait a minute. The bleed nipple is meant to release brake fluid not an intake. Even if you put a bleed nipple on the fork you will still need to refill at the fork cap. Not to mention the threads are different. If removing the fork drain screw is difficult because it is a straight slot screw, there are Allen head replacements.

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A brake bleeder works in both directions, hence the requirement to close the bleeder when the brake pedal is released.

Onder said:

I pulled front ends on two bikes with Roadholders last week. Both bikes less than 5k since previous change. Both showed black silt at the bottom of the slider leg. This is not unusual and I really think pulling the sliders off and cleaning everything is the way to go.

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I don't disagree but if you have black sludge after 5k, IMHO, you should change to a different oil.

When I could get it, I used SAE 20 and today SAE 30 in Nortons and older Triumphs. In other words, single viscosity and non-detergent. On some later Triumphs that were designed for it, ATF. The oil after a year or around 6000 miles should be changed, and it should be darker but there should be little to no sludge in the bottom.

Onder said:

I pulled front ends on two bikes with Roadholders last week. Both bikes less than 5k since previous change. Both showed black silt at the bottom of the slider leg. This is not unusual and I really think pulling the sliders off and cleaning everything is the way to go.

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The black silt is the rust/steel that has fallen off the springs or been rubbed off by the stanchion, internal springs are a problem with these deposits. You just have to compare oil that's been in BSA forks with external springs to see the effect. The BSA springs rust more but at least you can grease them which stops the rust, grease an internal spring and the oil will wash it off and the grease will contaminate the oil changing its viscosity.

kommando said:

The black silt is the rust/steel that has fallen off the springs or been rubbed off by the stanchion, internal springs are a problem with these deposits. You just have to compare oil that's been in BSA forks with external springs to see the effect. The BSA springs rust more but at least you can grease them which stops the rust, grease an internal spring and the oil will wash it off and the grease will contaminate the oil changing its viscosity.

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Agreed, especially if not ridden and moisture gets in the tubes (an August Virginia day would be bad for filling forks - today would be great). Everything clean, not rusted, used, and maintained, the rust should not be there. There can be some deposits from the bottom bushing rubbing inside the stanchion, but that should be minimal. Using an oil with detergent and/or viscosity modifiers will increase the mess since the forks never get to the temperatures those are meant for.

If a brake bleeder would work for draining fork oil Norton probably would have fit them from the get go. I know of no fork that uses them, but I have not purchased a new bike since 1996, and don't follow motorcycle design trends that close.

I put the bike up on a center stand remove the caps, slowly pull the springs out rag in one hand around the spring the other hand pulling the spring out. Then use a harbor freight pneumatic brake bleeder with a long flexible hose on it to get most of the oil out of the fork from up top. Then take the bleed screw/bolt whatever out and let the fork dribble for an hour into an oil pan. Then do the other side. Pump the rest out if you want.

Ideally you buy new seals and pull the forks apart each time. Very time consuming with some bikes. There's no other really good way to get them fully cleaned up without making a bigger mess pumping mineral spirits or whatever through them in situ.

I have never seen perfectly clean oil come out of a set of forks that had more than a couple hundred miles on them. Even brand spanking new forks. It usually turns greyish or at the very least changes color somewhat.