rcpaints: Fork Oil /Rebuild Q&A

[rcpaints]

A question for Harley riders. I ride a Goldwing trike and at 44000 mile just had my front forks rebuilt.

Question, Do Harley forks need to be rebuilt?
Thanks
Rcpaints

 

[Papa Zook]

Yes harley forks will need to be rebuilt but when will depend on several factors. What year and what model is it? Is it a trike conversion or factory trike and if so describe it? Does it have a rake kit? How many miles does it have? How is it ridden, ie, hard, easy, twisties, one up, two up? Without knowing all of these variables it could vary a lot in recommended service and re-build intervals.

The Harley factory service manual recommends a fork oil change at 50K miles, but the fork oil looks burnt way before that on most (trikes) I have seen. It costs very little more time and money to change the fork oil, bushings and seals all at the same time.

 

[nucseal]

The Harley factory service manual recommends a fork oil change at 50K miles, but the fork oil looks burnt way before that on most I have seen. It costs very little more time and money to change the fork oil, bushings and seals all at the same time.

So what is your recommendation, when to change fork fluid on a TriGlide?
Nuc

 

[Lee H. Mann]

It is a must at 20K..........ThumbUp

 

[Papa Zook]

It is a must at 20K..........ThumbUp

Not according to Harley, but I agree, 20K is a good time to change it. I know guys that ride theirs hard and change it every 10K.

 

[MB1953]

Yes harley forks will need to be rebuilt but when will depend on several factors. What year and what model is it? Is it a trike conversion or factory trike and if so describe it? Does it have a rake kit? How many miles does it have? How is it ridden, ie, hard, easy, twisties, one up, two up? Without knowing all of these variables it could vary a lot in recommended service and re-build intervals.

The Harley factory service manual recommends a fork oil change at 50K miles, but the fork oil looks burnt way before that on most I have seen. It costs very little more time and money to change the fork oil, bushings and seals all at the same time.

:Agree:
With the work he does on trikes, I think Zook should really know this front and back, and Lee as well. I let mine go to the recommended 50K, but I know that I could feel the difference as it got closer. 20 K sounds right on, Lee.



Of course, I was in at Space Coast HD to schedule my 50K service, cause I was determined to ride it till the wheels fell off, but they made me way too good an offer to trade up!

 

[roadking2]

I've changed the oil about every 25K or so. Other than that the only time I've ever done anything to the front was when I put lowering shocks in and when I triked my bike and put a raked tree on. Even way back when I first started riding Harleys I didn't have to do much to the front and that was back in 67 when I got myself an old 63 Duo Glide. I had to fix, replace, tighten, and repair a whole bunch of other stuff, but the front end didn't give me much to worry about. Never has.

 

[gerald martin]

fork oil

I don't understand the need to change fork oil unless the seals are leaking. The air shocks
in a Harley have oil in them and I have never heard of anyone changing the oil in them. The front forks are just a shock absorber so unless they are leaking why bother.
I am not wanting to start an argument but I would like advise on why fork oil needs to be changed

 

[Papa Zook]

Fork Oil

I don't understand the need to change fork oil unless the seals are leaking. The air shocks in a Harley have oil in them and I have never heard of anyone changing the oil in them. The front forks are just a shock absorber so unless they are leaking why bother.
I am not wanting to start an argument but I would like advise on why fork oil needs to be changed

Like most folks, your assumptions about shock oil longevity are wrong. Yes forks are shock absorbers, but the oil itself is the dampening agent. Without oil, it would be like riding on a pogo stick. Dampening occurs when the oil gets pushed through several small holes or orifices in the dampening tube upon compression and sucked back through these same holes when the springs recoil. The friction and pressure of the oil constantly being forced through these tiny holes gets the oil very hot.

If you dont believe it, take a 20 mile ride and drain the oil and it will almost burn you. That heat breaks down the oil and will change the viscosity and your forks will work less efficiently for suspension and braking. Fork seals also break down over time and allow moisture in thus further contaminating the oil.

Ive seen 50K mile fork oil come out black as soot.

What most dont consider is that pressure causes heat.

This is the principle that the diesel engine is built upon. The pressure is so great in a diesel engine that no spark plug is required, the pressure causes the ignition. Obviously shocks generate no where near that pressure but they do cause enough to generate substantial heat.



Another example of how pressure generates heat is the video below of a compression fire starter.

 

[Lee H. Mann]

My SuperGlide had 80,000 miles on it when I sold it.

Somewhere on this forum I expressed my own experiences with fork oil.

But I will be brief here with a personal story.:Angel:

I had a Harley SuperGlide in 1997-2002. I was a spirited rider (still am) and was putting 2,000 miles a month on my bike. I rode it EVERYWHERE and I mean everywhere. The Harley dealer near my home had demo rides at one of their Open House Events and I test rode a new Deuce. It rode so good compared to my SuperGlide and I was thinking of trading. While in that thought mode it was time to service my SuperGlide.

The 20,000 mile service guide said fork oil was to be changed. I changed it and the improvement was unbelievable. It rode like a NEW MOTORCYCLE again. I figured it had deteriorated over time and I really never even noticed the gradual change.

I never reconsidered the Deuce.



I change my fork fluid every 10,000 miles now and never look back. I don't suggest this to every rider except the spirited ones. I now run 20-50 Amsoil in my FXR forks and it handles like a sport bike even with a 21" tire and no more pogo stick. I was running 10-30 Amsoil in my Road King before I sold it.

I have probably changed the fork oil in over 150 different motorcycles in the last 10 years and have made some very compelling observations. The 41mm Harley forks are very hard on the fork oil even at 10,000 miles. I change them over to Amsoil ATF and they appear to be pretty clean at the next 10K interval. The Goldwings are not quite as severe but should still have their fluid change by at least 20,000 miles. At 40,000 miles the Goldwing should have fork bushings and seals replaced.

The most abused part of the motorcycle is the front forks and probably less than 10% of the riders ever consider changing the oil.

Most motorcycle shops don't seem to care either. More than likely your fork oil is shot and you don't even know it and your ride is getting worse.

Not very brief after all.:xzqxz:

 

[Gorilla]

It sure was nice when they had a drain plug on the HD forks. Made the frequent oil change easier. Now you got to pull the lowers to change the oil or the whole fork if you don't have a tool to get the seal in with the fork attached.. I guess it makes you go ahead and consider the seals after all its apart.

 

[gerald martin]

seems strange

I have been reading the posts on fork oil change as we are doing a spring change on the forks of a 2006 fatboy. At 86,000 kilometers we drained the fork oil into a glass container. We then put new fork oil in another glass container. The colors of both oils was identical. If you would have asked anyone to guess which oil had the 86,000 kilometres on it they would not be able to tell. This bike was driven normally, not aggressive and not babied

 

[Lee H. Mann]

Pseudo-science is always a good justification for saving a buck !:qpnmt:

 

[gerald martin]

fork oil

it is not pseudo it is a fact. No one changes oil in the hydraulics of a tractor or any other hydraulically operated equipment. Of course if the seals are leaking it will get contaminated and needs to be serviced other wise it will never get hot enough to start to breakdown. Of course this is only my opinion and also the opinion of many certified mechanics that aren't out to squeeze a dollar out of the misinformed

 

[Lee H. Mann]

Here is another opinion

Read the last line !
http://www.motorcyclistonline.com/how-to/oil-change-intervals-your-suspension-street-savvy

 

[rhino 2]

it is not pseudo it is a fact. No one changes oil in the hydraulics of a tractor or any other hydraulically operated equipment. Of course if the seals are leaking it will get contaminated and needs to be serviced other wise it will never get hot enough to start to breakdown. Of course this is only my opinion and also the opinion of many certified mechanics that aren't out to squeeze a dollar out of the misinformed

I have a Kubota 6800, And i can tell you that after working the bucket for a short time the Hydraulic fluid gets very hot... Just saying...:Shrug:

 

[gerald martin]

fork oil

Do whatever you want. I myself have owned and driven a Harley for 55 plus years. yes I have changed fork oil many times but only when replacing worn out seals and have never had a problem. Also I have never seen extremely dirty oil when I did change it On the other hand repacking the steering head bearings is a must in my books as they are subjected to a lot of dirt, high pressure washing ext.

 

[Sloufoot]

it is not pseudo it is a fact. No one changes oil in the hydraulics of a tractor or any other hydraulically operated equipment. Of course if the seals are leaking it will get contaminated and needs to be serviced other wise it will never get hot enough to start to breakdown. Of course this is only my opinion and also the opinion of many certified mechanics that aren't out to squeeze a dollar out of the misinformed

Not to hi-jack this thread, but I must set something straight here. Your certified mechanics have never worked around much hydraulics ! Hydraulics when worked hard will heat. I don't mean just a little, but hot enough to burn paint off tanks, cylinders, controls, pumps & motors. Also melt hoses. It isn't impossible for a hydraulic to normally operate in excess of 300*F. Part of my job for most of my career was to monitor the quality of oil.

We tested for contamination, & viscosity on the average 3 to 4 times a year on all machinery.

Or whenever we had the system down or open.



A lot of our machinery had to keep contamination around 4 micron, never above 8 micron. A lot of hyd oils is around 10 micron brand new. We used electronic filters to get it down to spec. Some months we would go through a thousand gallons of hyd oil just because of contamination. That was just in the area I worked. Many thousands of gallons railroad system wide per month. All because of failure of the oil, or contamination. Much of the failure from heat.

Any time oil is forced through an orifice expect it to heat.

The shocks operate forcing oil through orifices. IT will get hot damn hot !

When oil passes through a restriction it will actually wear the hole some also. Parts rubbing against other parts will wear leaving contamination in the oil.

Enough rant !

Just say'n !
Have a nice day

 

[Lee H. Mann]

Just sayin'
http://www.triketalk.com/forum/threads/19195-How-Many-Have-Had-Their-Triglide-Fork-Oil-Changed

 

[Sloufoot]

Just sayin'
http://www.triketalk.com/forum/threads/19195-How-Many-Have-Had-Their-Triglide-Fork-Oil-Changed

Did you ever figure out why there is two different sliders for the FLHTCUTG & the FLHTCU ? The rebuild kit is the same. The only difference is the drain screw & part #.

 

[Lee H. Mann]

Funny you should ask. I was looking tonight at part numbers to see where they made changes between 2009 and 2014. Different axles but the same bearings, different fork tubes and different lower legs but the same seals.... without one to examine against the other, I cannot make a determination. Without 2 assemblies next to each other, can't tell the difference in length. The obvious difference is the solid R/H lower and lack of drain screw.

 

[Sloufoot]

I think the reasoning behind the elimination of the drain was three fold.
1st- Less cost to manufacture. Sells for the same price.
2nd- More money in the service end for the dealer/Techs.
3rd- More money from worn parts from a 50,000 mile service interval. Where if you could drain at 10,000mi. you might keep it changed.

 

[Lee H. Mann]

I have been reading the posts on fork oil change as we are doing a spring change on the forks of a 2006 fatboy. At 86,000 kilometers we drained the fork oil into a glass container. We then put new fork oil in another glass container. The colors of both oils was identical. If you would have asked anyone to guess which oil had the 86,000 kilometres on it they would not be able to tell. This bike was driven normally, not aggressive and not babied

it is not pseudo it is a fact. No one changes oil in the hydraulics of a tractor or any other hydraulically operated equipment. Of course if the seals are leaking it will get contaminated and needs to be serviced other wise it will never get hot enough to start to breakdown. Of course this is only my opinion and also the opinion of many certified mechanics that aren't out to squeeze a dollar out of the misinformed

Do whatever you want. I myself have owned and driven a Harley for 55 plus years.

yes I have changed fork oil many times but only when replacing worn out seals and have never had a problem. Also I have never seen extremely dirty oil when I did change it On the other hand repacking the steering head bearings is a must in my books as they are subjected to a lot of dirt, high pressure washing ext.

This one below had to be completely overhauled with bushings and seals. It had also be Babied. The real interesting thing here is this motorcycle weighs half of what an FLH-FLT does and has the same size forks.