Took the NT to see the Seal Doctor

[NewTo700V]

Yeah, corny title.

The NT greeted me this afternoon with an incontinent right fork seal. It had piddled over the dust seal and a bit down the slider. I had just dealt with a fork leak on another bike the other day. I'm leaning towards residual road salt and sand getting in there. Wiped down the fork, pried up dust cover, wiped down fork again, attached Seal Doctor for a few passes until gunk stopped collecting. I gave the NT a dozen plus forward lunge brake slams with the dust cover still up, no oil collecting on the fork tube. Then I cleaned the inside of the dust cover with the other end of the Seal Doctor. Dust cover back down, now just need to log some miles. There was no fork "blow out" events so I'm hopeful a cleaning is all that was needed.

 

[Pbro63]

Yeah, corny title.

The NT greeted me this afternoon with an incontinent right fork seal. It had piddled over the dust seal and a bit down the slider. I had just dealt with a fork leak on another bike the other day. I'm leaning towards residual road salt and sand getting in there. Wiped down the fork, pried up dust cover, wiped down fork again, attached Seal Doctor for a few passes until gunk stopped collecting. I gave the NT a dozen plus forward lunge brake slams with the dust cover still up, no oil collecting on the fork tube. Then I cleaned the inside of the dust cover with the other end of the Seal Doctor. Dust cover back down, now just need to log some miles. There was no fork "blow out" events so I'm hopeful a cleaning is all that was needed.

After my first two up mountain jaunt the other week, I notice the purplish fluid collecting on the ground in the garage underneath the radiator. Thought what the heck is this and where did it come from. Turned out the heavy pitting on the fork tube did not introduce itself to the fork seal until riding two up had used up all available spring travel. Well the fork oil gushed out and followed gravity down onto the front fender all the way to the rear most point of the fender far away from the fork, hence the confusion. Well I'll have to order a pair of fork seals and have at it...
Does anyone have advice on best practices to replace the fork seals?

 

[NewTo700V]

If you have heavy pitting in areas of seal travel you need new fork tubes, not just seals.

As for best practices...

I prefer a fit size Motion Pro Ringer driver to the universal versions (NT forks are 41mm)

Buy spare hex cap bolts that go in the bottom of the fork (securing damper assembly) incase the old ones get rounded out upon removal. The copper crush washers for the bolts. You can anneal them with a torch for extra squishy sealing ability to be sure.



Crack fork tube caps loose before loosening triple clamps.

Take photos of brake line, wire, and cable routing around forks so they can be routed back properly after reinstall.

A cut and lubed thin sandwich baggy over tube end while sliding over seal.

A good digital torque wrench. I have one from AC Delco that does from like 2.5 to 39 ftlbs.

A service manual on hand.

Syringe style fork oil level setter makes life easy.

Very fine grit (like 1500) wet sanding sponges for gently cleaning fork tubes above seal travel area. Like rust build up around lower clamp area.

Set down clean moving blankets for work area.

#1 - Take your time.

 

[DirtFlier]

An AC/Delco torque wrench? I knew they made auto parts but never heard of them making tools.

 

[NewTo700V]

Yes. I bought this one a while ago on sale. Specifically for the job of front fork tear downs. The range is good for the lowest stuff (bottom damper bolt) up to the higher end (bottom yoke clamp bolts). It isn't sufficient to do something like the steering stem nut, but that's outside the scope of this repair.

https://www.amazon.com/ACDelco-ARM601-3-Digital-ft-lbs-Notification/dp/B004VYUQI2/ref=mp_s_a_1_2?dchild=1&keywords=arm601&qid=1614719776&sr=8-2

 

[Phil Tarman]

Since I put fork gaiters on Dudley, I haven't had any fork problems. I did have the fluid changes about a year ago. Joe had put gaiters on Horse before I bought him. Gaiters are worth the money. Triumph gaiters fit (don't remember which ones I got, but I think they were for a '13-ish Bonneville. Joe used some of the wraparound ones and they seem to work fine.

 

[Pbro63]

If you have heavy pitting in areas of seal travel you need new fork tubes, not just seals.

As for best practices...

I prefer a fit size Motion Pro Ringer driver to the universal versions (NT forks are 41mm)

Buy spare hex cap bolts that go in the bottom of the fork (securing damper assembly) incase the old ones get rounded out upon removal. The copper crush washers for the bolts. You can anneal them with a torch for extra squishy sealing ability to be sure.



Crack fork tube caps loose before loosening triple clamps.

Take photos of brake line, wire, and cable routing around forks so they can be routed back properly after reinstall.

A cut and lubed thin sandwich baggy over tube end while sliding over seal.

A good digital torque wrench. I have one from AC Delco that does from like 2.5 to 39 ftlbs.

A service manual on hand.

Syringe style fork oil level setter makes life easy.

Very fine grit (like 1500) wet sanding sponges for gently cleaning fork tubes above seal travel area. Like rust build up around lower clamp area.

Set down clean moving blankets for work area.

#1 - Take your time.

Thanks very much for the thorough reply.

As for new fork tubes I think I'll try to fix / replace the seals first. My assumption is since the pits are at the very end of the fork suspension travel, it is that one good breaking event two-up that caused the fork to use all available travel and at that point the pitted section gouged the fork seal as noted by the sudden profuse leakage. So after perusing on line I will attempt to sand down the pits with emery cloth. As long as no damage will be caused to the new fork seal I can live with the occasional minute (minoot : ) amount of oil that may get by a depression in the extreme end of the fork travel. Well at least that's my theory. People have spoke of also filling the depression with epoxy after sanding and then resanding. May try that too as no further harm can come from it ?

 

[ARKNT]

I have used the emery paper method. The pits I had were sharp edged and smoothing the edges helped to stop cutting the seals.
Just use very fine emery to round the edges. Should help.

Brad

 

[NewTo700V]

Something like 50-60 miles on the NT this morning running errands. No sign of oil.

Everyone should have one of these Seal Doctors in their tool box. Yes you can do the same with 35mm film, cut milk jugs, or the Seal Mate but none of those are as easy to use. The raised surfaces on the Seal Doctor that give your fingers purchase to spin the cleaner around really makes a huge difference. Spend the extra cash and save on the cursing.

 

[NewTo700V]

Another 200 miles for the NT over the weekend. No oil. Other bike has like 350 miles now since cleaning, also dry.