Fork Oil Flush Recommendation

I have had my NT since June of 2010. Last summer I had the dealer perform a brake fluid flush and a coolant flush and replace. At that time I also asked them to replace the fork oil. They told me they did not recommend replacing the fork oil until the seals were leaking and needed to be replaced. Due to the high labor cost of pulling the forks and doing the work it seemed to be logical that you would not want to go to that expense to replace the fork oil only to have to do it again when the fork seals started to leak so I took their advice and let it go. This summer my NT will be 6 years old and still no fork seal leaking. I read in another post where Chuck said his ST1300 had to have the fork seals replaced at 100,000 miles. I had thought about as a preventative measure to replace the seals and fork oil at the same time but that might just be a waste of money if the fork oil and seals are still good. What say you, leave well enough alone or take some other course of action?

Warren you can suck the fork oil (most of it) out from the top without taking the fork apart. Of course this method doesn't allow cleaning everything before refilling. I've always been amazed at how dark and nasty the fork oil looks in any fork I have opened up. Maybe the oil is OK, but it sure looks bad. I used a small tube to suck the oil out and replace it with what I hope is compatible (universal) fork oil. It has been OK for the last 12,000 miles.

I, too, thought about replacing my fork seals before they start leaking. I'd rather not be 2,000 miles from home when they do start to leak. I decided to wait on my 2011. But don't blame me if your seals start leaking tomorrow.

Forgot to say you can get ALL the oil out by inverting the motorcycle, but that is difficult and messy. I haven't tried it.

I had my fork oil changed at 30K miles and the Honda dealer recommend changing the fork oil every 30k. They must have sucked it out as the cost was minimal.

Terry

It wouldn't hurt to suck the oil out the top but most of the heavier metal wear particles will be at the bottom where you cannot get to them.
I would probably lean more towards removing the forks to invert and drain or leave them alone and wait for seals to give out.

Brad

It isn't just the seals you need to be thinking about. The bushings inside the fork wear and at some point need to be replaced. I recall someone rebuilding their forks on an NT and the bushings looking good. I don't recall what the mileage was. I believe it is the wear of those busgings that is partly to blame for the fork oil looking so bad. The bushings are toast after 25-30k on my GL1800, yet after 100k the bushings in my buddy's Venture still looked okay. The problem is, you don't know until you open the forks up and look at them.

If you are considering having your forks serviced, I would have the entire system done. After inspecting the wearable parts, you will know better on how long you can go the next time. Pulling the forks and servicing them is not difficult. I would think about on par with a valve clearance check in terms of shop time. Pretty straight forward stuff. And the internal fork parts should be less than $100 (seals, bushings, dust covers, and oil).

Excessive wear on the bushings could also cause the fork seals to weep prematurely because more "wobble" at the top may be more than the elasticity of the seals can control. I agree that fork service is a real pain but I do it anyhow about every 25-30k miles, with the fork taken completely apart and cleaned. And I always find lots of grunge at the bottom of the fork slider.

ps. I'm a nut about suspension stuff and agree that 98% of riders never even change fork oil, let alone disassemble & clean the fork.

I have mine changed about every 2 front tyres (about 30,000 miles ish). As they've got the wheel off to change the tyre, pulling the forks isn't such a big job.

I usually get my tyres changed at a service interval rather than waiting till they're right on the limit to keep the labour costs down.

warren, maybe you can take off forks yourself, take them to dealer to save that labor cost?? wheel, fender, then 2 bolts each side on forks. I take mine off for my homegrown Honda mechanic. all you need is come weight on seat or in top box will keep it from falling over. actually just removing front wheel with no weight it won't fall forward. that center stand is so teeter todder. my mechanic guy replaced seals and copper crush washers, and the oil @93,443 miles

Woodaddict said:

warren, maybe you can take off forks yourself, take them to dealer to save that labor cost?? wheel, fender, then 2 bolts each side on forks. I take mine off for my homegrown Honda mechanic. all you need is come weight on seat or in top box will keep it from falling over. actually just removing front wheel with no weight it won't fall forward. that center stand is so teeter todder. my mechanic guy replaced seals and copper crush washers, and the oil @93,443 miles

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David, Do I read this correctly that the first time you changed the fork oil was at 93K miles when you also had the seals replaced ?

yepper........

I don't understand why a competent MC Mechanic (Independent) can't put drain plugs on the bottom of each fork leg. That would make it easy to drain each fork leg, run some solvent through, and refill. My Roadholder Forks on my 71 Norton had these drain plugs and I had no problem with changing the oil at regular intervals. I used ATF as the solvent.

Bear said:

I don't understand why a competent MC Mechanic (Independent) can't put drain plugs on the bottom of each fork leg. That would make it easy to drain each fork leg, run some solvent through, and refill. My Roadholder Forks on my 71 Norton had these drain plugs and I had no problem with changing the oil at regular intervals. I used ATF as the solvent.

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That worked on my Concours 10 and I was happy with it.
But I haven't had the NT apart to see how much room there is and if the wall thickness would allow a pipe thread tap.
Anyone else know?

If I remember correctly someone on this list did add the screws to the bottom of the fork legs. I think it might have been charlie b

Most (all?) of my off-road Huskys had drain screws in the early-70s and I never liked the way it took forever for the old grunge to come out.

DirtFlier said:

Most (all?) of my off-road Huskys had drain screws in the early-70s and I never liked the way it took forever for the old grunge to come out.

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That is why I used ATF to flush the forks. Of course one has to know how many Ml the fork takes. I'm going to try to find out how thick that fork wall is and if it can be tapped.

Bear said:

I'm going to try to find out how thick that fork wall is and if it can be tapped.

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Check the UK forum. I vaguely recall a discussion about that on it....

I have a 2011 NT & just turned 10k miles on it.

Took it in to get some tires & was informed my front forks are leaking.
I don't claim to know anything about mechanics but from reading this post
It appears that with only 10k miles the forks are leaking prematurely.

I would say so although there are variables that might effect the life. One is to keep the fork tubes clean. Bug parts can grind up the seals.

Warren said:

I would say so although there are variables that might effect the life. One is to keep the fork tubes clean. Bug parts can grind up the seals.

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This is true, but sometimes the seals can be cleaned. Motion-Pro makes a "tool" called, IIRC, the Forkmate which is a piece of plastic about the size and stiffness of old 35mm film (remember that?) that you can run down between the seal and the fork. It's worked for me a couple of times to save seals that were slightly leaking.

After I'd used that tool once or twice, my seals were gone and I bought a set of fork gaiters from Triumph (can't remember the part number but it was whatever fit the forks on a Bonneville) and had my wrench install those when he replaced the seals and bushings at about 50K miles. Since then, I've had the forks serviced again at about 90-95K miles but the seals haven't leaked again.

jojococomo said:

I have a 2011 NT & just turned 10k miles on it.

Took it in to get some tires & was informed my front forks are leaking.
I don't claim to know anything about mechanics but from reading this post
It appears that with only 10k miles the forks are leaking prematurely. 

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sometimes its not miles, but age in that hot OK sun and dust and bugs