Fork oil change

potter0o

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I finished this up today for the second time. Much easier this time around and I had purchased the Tusk fork oil tool which was helpful. Does anyone use any grease or anti seize where the forks get clamped? I get some small rust build up here that I buff away. Was just thinking about more protection for the future.
 
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kaz

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Sorry if it sounds silly, I may be missing something, but what happens if you remove only the fork caps, suck out oil with a big syringe and a long tube, and put in an equal amount of new oil?

I know this skips the spring measurement and goop cleanup, but if I assume no one ever did it on my bike, and I don't want to remove all the forkery just yet, is there any merit in the above method?
 

670cc

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Sorry if it sounds silly, I may be missing something, but what happens if you remove only the fork caps, suck out oil with a big syringe and a long tube, and put in an equal amount of new oil?

I know this skips the spring measurement and goop cleanup, but if I assume no one ever did it on my bike, and I don't want to remove all the forkery just yet, is there any merit in the above method?

I think there's merit to doing it this way as a "semi" fork oil change - better than nothing. It will save a LOT of work in not having to remove the forks from the bike, but you will not likely be able to replace all of the oil, just some of it. The key to success would be in accurately measuring and replacing the exact amount of oil removed. If you error, the fork oil level will be low or high, which changes the amount of compressible air in the tube, affecting the "stiffness" of the ride.
 

dduelin

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Sorry if it sounds silly, I may be missing something, but what happens if you remove only the fork caps, suck out oil with a big syringe and a long tube, and put in an equal amount of new oil?

I know this skips the spring measurement and goop cleanup, but if I assume no one ever did it on my bike, and I don't want to remove all the forkery just yet, is there any merit in the above method?
I'm too meticulous to do an oil change this way but it stands to reason one would get most of the benefit of changing it properly.

A caveat concerning replacing the fork cap. Some force is needed to press the cap down onto the fork tube combined with a twist to engage the threads without cross-threading them. If you don't have risers the handlebar and cables are kind of in the way of a straight shot at this. I just find this easier to do with the fork tube free and in one hand and the other hand pressing the cap down. It's easier for me to turn the tube onto the cap instead of the cap in to the tube.
 

kaz

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I think there's merit to doing it this way as a "semi" fork oil change - better than nothing. It will save a LOT of work in not having to remove the forks from the bike, but you will not likely be able to replace all of the oil, just some of it. The key to success would be in accurately measuring and replacing the exact amount of oil removed. If you error, the fork oil level will be low or high, which changes the amount of compressible air in the tube, affecting the "stiffness" of the ride.

Thanks, looks like I need to get a big pitcher with dials from some cookware store.


I use a manual vacuum extractor and do exactly what you describe. You should be able to get right about 475ml out with the forks extended (on center stand) of the 515ml that is supposedly in there.

Remember, only one cap at a time unless you have it on a front stand.

Sweet. Which extractor are you using? Which fluid? I thought I could put some weight on the rear while the bike is on the center stand to lift the front up.

Did you encounter the problem dduelin is describing, turning the cap into the fork when replacing?

I'm too meticulous to do an oil change this way but it stands to reason one would get most of the benefit of changing it properly.

A caveat concerning replacing the fork cap. Some force is needed to press the cap down onto the fork tube combined with a twist to engage the threads without cross-threading them. If you don't have risers the handlebar and cables are kind of in the way of a straight shot at this. I just find this easier to do with the fork tube free and in one hand and the other hand pressing the cap down. It's easier for me to turn the tube onto the cap instead of the cap in to the tube.

Good to know. I do have a set of 2cm risers with a little tilt off ebay that I didn't install yet.

Does your SS-47 fluid recommendation still stand?
 

Therapy

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If/when I take the forks off and drain I think drilling a drain plug would be plan.
Has anyone done this.
All my bikes from the past had these.
Are they not there now to force shop fees? (or new fork/bike sales)
 

670cc

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Sorry if it sounds silly, I may be missing something, but what happens if you remove only the fork caps, suck out oil with a big syringe and a long tube, and put in an equal amount of new oil?

I know this skips the spring measurement and goop cleanup, but if I assume no one ever did it on my bike, and I don't want to remove all the forkery just yet, is there any merit in the above method?

One other thought came to mind. If the fork has Racetech Gold Valve Emulators installed, the emulators sit on top of the damper tube and block access to the bottom of the fork. This would severely limit the amount of oil one could extract with a vacuum pump.

I've easily removed and installed the fork caps many times with the forks mounted on the bike, mainly to adjust the afore mentioned emulators. I also have 2" Rox risers installed. Take weight off the front of the bike so the forks wont compress when spring tension is removed when the cap comes off. Do only one side at a time unless the front end of the bike is fully supported.
 

dduelin

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As you can see in the original post there is very little required to make a fork oil level tool. An inexpensive syringe and a length of vinyl tubing that is cut to a length that corresponds with the distance down to the desired level. The last item on your selection looks like it would do it. Note that Honda's method of measuring the level requires removing the spring, spacer, and washer but you should be able to do that with a piece of wire bent into a hook.
 

dduelin

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KAZ, all correct but key here is fork oil level is measured with forks compressed. So you'll have to remove the wheel to independently compress each fork if you use the measurement method. Follow the shop manual description of how it's done: Pour the specified amount of recommended fork fluid into the fork pipe. Slowly pump the fork pipe several times to remove any trapped air from the lower portion of the fork pipe. Compress the fork pipe fully and measure the fluid level from the top of the fork pipe.

I have a 6 liter Pela extractor, but there are others out there.

I have heavier springs, so shorter pre-load spacers for me; hence caps go on with very little effort. You'll need to determine if a change in pre-load is needed by sag measurements.

This is true and I forgot about the need to compress the forks. I suppose if we had a fork out of the bike we could measure 104 mm depth compressed and then extend the fork and take another measurement of level so ascertain the extended level. Maybe next time I'll do that.
 

670cc

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Kaz could take a fork oil level measurement prior to removing oil from the extended fork, then fill back to that level. The problem is that the spring is in the way of getting a good measurement, but a crude measurement could be made. One would need to be aware that the fork is at an angle from vertical as mounted on the bike, and would also need to assume the level was correct when beginning the procedure. It’s not the ideal situation.
 
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dduelin

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Kaz could take a fork oil level measurement prior to removing oil from the extended fork, then fill back to that level. The problem is that the spring is in the way of getting a good measurement, but a crude measurement could be made. One would need to be aware that the fork is at an angle from vertical as mounted on the bike, and would also need to assume the level was correct when beginning the procedure. It’s not the ideal situation.
Trying to change it half-asked is not ideal, I think we agree on that. Having just replaced steering bearings on the Wing I'm thinking a proper fork oil job on the NC is a simple half day job but not everyone sees it that way.
 

kaz

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What about the first idea, of measuring exactly how much I extract with the syringe, and putting back the exact same amount? Would that not be sufficient for going from super dirty to not that dirty?
 

bobk100

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Hi All

This is a bit after the OP's but can anyone tell me what is the correct oil to put in the forks and what the service period is to do it?

Can't find the answer online or the book.

I think when it comes to my next front tyre change I might drop the legs out and do an oil change. Might be tempted to take them to my local 'go to' man and get him to drill and tap the bottom of the legs to extract the oil in future.

Cheers
 

dduelin

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Honda spec is Honda SS-47 which is nominally a 10w fork oil.

There is no recommended service interval for this job. I try to do it every 15 to 20,000 miles.
 

bobk100

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Cheers dduelin. 10w it will be.

Wonder if my go to man could put in some brake bleed nipples on the bottom of the fork legs, that'd make it even easier.

Had this bike less than a week and it's really growing on me. Particularly the fuel consumption. After 20yrs on a Funduro I thought it would take a lot of getting used too.

Regards
 

dduelin

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Cheers dduelin. 10w it will be.

Wonder if my go to man could put in some brake bleed nipples on the bottom of the fork legs, that'd make it even easier.

Had this bike less than a week and it's really growing on me. Particularly the fuel consumption. After 20yrs on a Funduro I thought it would take a lot of getting used too.

Regards
Well, it’s not something you’re doing all the time.
 

halfSpinDoctor

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Great write-up, thanks for sharing.

These are 6 mm allen head bolts and the clearance is tight. I could not use a rachet handle but a breaker bar just fit inside the fairing. I could have removed the fairing to gain more access but I did not.

Those 6 mm top clamp bolts are such a pain! I scratched up the inner plastic of the fairing pretty badly trying to put them back in and torqued to spec.

I ended up finding a stubby 6 mm Allen socket on eBay. It's not a super high quality tool, about $3 shipped, but highly recommended to minimise frustration or scratches.

I got a 3/8" drive, but there are quite options in 1/4" drive that might be even shorter.

 

GregC

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Is a fork seal tool necessary when replacing the fork seals? Saw Dave’s DIY version in this thread, but wondered if it’s necessary or if other common tools will do?
 
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