Fork oil fluid level

[faser41]

I recently bought a 1986 FJ with only 20k miles, stock. The manual says 14.3oz. of fresh fluid (per leg) but does anybody know in terms of height from the fluid to the top of the tubes should be in inches? I'm only removing the cap with spring and damper rod at this point, so it's a simple fluid change. Thanks in advance (tia) and i'll check back in a couple of hours.

[yamaha fj rider]

150 mm as per Yamaha. Race Tech and some others say, you can go as high as 130 mm. That is springs out and fully compressed.

Kurt

[faser41]

Oh cool thanks for the info Kurt I really appreciate that! So just over 5" I guess? Yeah springs are out and is fully compressed. As an aside I bought some forks from a '91 and want to do the conversion to 17" and get rid of the anti-dive unit, and I'd like to find a pair with real good rotors also to replace mine but the tire tread is at like 95%+ ...........new rotors stock would cost me over $240 each and I've already had to buy a new battery, left hand mirror, plugs, front brake pads and all fluids, it needs new chain and sprockets................yeah it's starting to grow on me alright lol!!!

[FJscott]

Oh cool thanks for the info Kurt I really appreciate that! So just over 5" I guess? Yeah springs are out and is fully compressed. As an aside I bought some forks from a '91 and want to do the conversion to 17" and get rid of the anti-dive unit, and I'd like to find a pair with real good rotors also to replace mine but the tire tread is at like 95%+ ...........new rotors stock would cost me over $240 each and I've already had to buy a new battery, left hand mirror, plugs, front brake pads and all fluids, it needs new chain and sprockets................yeah it's starting to grow on me alright lol!!!

Ive got rotors that came off my 92, stock and wave rotors. have good chain and sprockets too,
left over from my gixxer conversion. you can have them for a song. PM me if you need them.

Scott

[faser41]

Thankyou Scott, doing so right now.....!

[red]

150 mm as per Yamaha. Race Tech and some others say, you can go as high as 130 mm. That is springs out and fully compressed.
Kurt

Okay, I guess, but what I really want to know is the actual fork oil level, measured on the outside of the fork in some reliable way, when the bike is on the center stand.  I want to be able to drain the forks, and replace the fork oil, without any dis-assembly of the forks.  I would drill a hole in each fork at that correct oil level, weld a nut over the hole, and insert a tube to add the fresh oil.  Then remove the tube, install a screw into the nut, to seal the hole again, until the next fork-oil change.  The sealing screw would be short; it would not intrude into the fork interior.  Yeah, I know, this method probably makes 'way too much sense.     

Does anybody have the actual fork oil level measurement, forks fully extended, but otherwise ready to ride?

Thanks,
Red

[racerrad8]

I would drill a hole in each fork at that correct oil level, weld a nut over the hole, and insert a tube to add the fresh oil.  Then remove the tube, install a screw into the nut, to seal the hole again, until the next fork-oil change.
Red

Well, a couple of things coming into my mind right away.

#1 - The location of the oil level "nut" in relation to the lower triple tree. If the nut is between the triple tree there would be no way to slide the fork tubes in or out. If were below the triple tree could it interfere with the full compression travel of the forks.

#2 - The different of the damper rod within the fork altering the range of travel of the forks. The later model forks use a shorter damper rod and they will top-out sooner than the early model damper rod.

If you need to ensure the proper level, you should use a tool the measures the oil from the top of the fork tube. Since you have to remove the upped cap to break the vacuum seal and allow the oil to vent and drain all you have to do is remove the springs, compress the forks and set the oil level.

Here is the tool I use and sell; fork oil level tool

Randy - RPM

[FJ_Hooligan]

I was looking through my maintenance notes last night and saw a note where I measured the oil level with the forks extended and the springs installed of 12 inches.

It would be nice if someone else would make a similar confirming measurement.  Hint, hint...........

[racerrad8]

...I measured the oil level with the forks extended and the springs installed of 12 inches.

Well, 12" looks like it puts it right about centered in the lower triple tree.

Randy - RPM

[red]

I would drill a hole in each fork at that correct oil level, weld a nut over the hole, and insert a tube to add the fresh oil.  Then remove the tube, install a screw into the nut, to seal the hole again, until the next fork-oil change.
Red

#1 - The location of the oil level "nut" in relation to the lower triple tree. If the nut is between the triple tree there would be no way to slide the fork tubes in or out. If were below the triple tree could it interfere with the full compression travel of the forks.
#2 - The different of the damper rod within the fork altering the range of travel of the forks. The later model forks use a shorter damper rod and they will top-out sooner than the early model damper rod.
If you need to ensure the proper level, you should use a tool the measures the oil from the top of the fork tube. Since you have to remove the upped cap to break the vacuum seal and allow the oil to vent and drain all you have to do is remove the springs, compress the forks and set the oil level.
Randy - RPM

Randy,

I am trying to avoid removing and replacing the fork caps, here.  Compressing the springs to replace the caps, can be hazardous to your health.  Using pre-load spacers only makes the job more risky.  One member here claims he almost lost an eye when that job did not go exactly right.  Even with a face-shield, the risks seem needless, in very real terms.  Yeah, I know, "we have always done it that old way."

I can give a bit on the first item, if needed.  Forget the nut, then.  Either drill and tap the hole into the fork instead, and just use a short machine screw to seal the filling hole, or seal the filling hole with aluminum tape, and install a screw-type automotive hose clamp to secure the tape firmly in place.  Remove the sealing screw (or hose clamp and tape), if you need to remove the forks.  With the drain screw removed and the filling hole open, I believe there will be no vacuum seal, and the old oil in the forks will drain out.  If the filling hole is within the travel range of the forks in compression, that would be a serious problem here, but I'm betting that the fork oil level (the filling hole) would be above that range.

No matter what rods are used in the forks, there will be some certain oil level in the forks, once everything is set up correctly, and that is the oil level that I am interested in knowing.  I do not doubt that the various years of manufacture will have a fork oil level specific to that hardware, but it should be "knowable" for each configuration.

The location of the new filling hole in the fork tubes should be at the correct level of the fork oil, with everything together, and the forks fully extended.  Replace the drain screw, refill the forks with fork oil to that level, seal the filling hole, and the job is done.

Cheers,
Red

[racerrad8]

Randy,

Compressing the springs to replace the caps, can be hazardous to your health.  

I can give a bit on the first item, if needed.  Forget the nut, then.  Either drill and tap the hole into the fork instead, and just use a short machine screw to seal the filling hole, or seal the filling hole with aluminum tape, and install a screw-type automotive hose clamp to secure the tape firmly in place.  Remove the sealing screw (or hose clamp and tape), if you need to remove the forks.  With the drain screw removed and the filling hole open, I believe there will be no vacuum seal, and the old oil in the forks will drain out.  If the filling hole is within the travel range of the forks in compression, that would be a serious problem here, but I'm betting that the fork oil level (the filling hole) would be above that range.

I do not doubt that the various years of manufacture will have a fork oil level specific to that hardware, but it should be "knowable" for each configuration.

The location of the new filling hole in the fork tubes should be at the correct level of the fork oil, with everything together, and the forks fully extended.  Replace the drain screw, refill the forks with fork oil to that level, seal the filling hole, and the job is done.

Cheers,
Red

The spring preload concerns seem odd...

The only way there is enough spring preload to cause the spring to shoot out and be hazardous to your health is if the bike is not supported when you are removing the cap and the weight of the bike slams down as the cap is removed. BTDTO

Now your idea about a nut is going to be the best solution to try and seal the oil into the fork tube. At least you will have a flat surface to use the head of a screw to seal.

You do realize that the compression of the forks causes the oil to pressurize and if there is a weak spot it will leak.

Now, if you have the forks fully extended, without any weight on the front tire to refill the forks, then that would be the level of your vent/fill port. Once you put weight back onto the front tire the fill hole is going to under the top of the oil level once the bike is placed back down into riding position and the hole must be sealed because there is now a pressure build up with the weight on the oil & air gap at the top of the fork tube.

aluminum tape and a hose clamp; talk about hazardous to your health.

The fork tube about about 2.5mm or .100" thick, so there is not enough material there to tap for threads plus you are going to have to try and obtain a seal on the curved outer surface of the fork tube.

Then there is the internal parts moving up & down inside the forks, so you can't have anything protruding inside as they will cause the forks to stop travel and you will crash...which is probably a bigger hazard to your health.

Sure, you can sort out the different fork level oils for different damper rods, but what about differences in springs as far a length and diameter causing differing displacements, how do you adjust the oil level for that?

Red, don't get me wrong, there are things that can improved upon and I hope you can sort a way to make it work for your benefit, but if your concern is the spring preload and possibly losing an eye, then I think your concerns are misguided.

We build a lot of forks here at RPM and the are all done very easily on the bench with the palm of my had removing the fork caps. The same for reinstalling them, the palm of my hand.

I get your idea, but just by the number of 12" given by Hooli, your oil level port is going to be interfering with the lower triple tree, so unless you drill & seal the triple tree and use an o-ring seal between the two I am not sure how you can make it work.

and finally, if you are running any type of fork valve, the valve must be removed to drain the oil completely, so the tops of the forks have to come off.

Randy - RPM

[ribbert]

I am trying to avoid removing and replacing the fork caps, here.  Compressing the springs to replace the caps, can be hazardous to your health.  Using pre-load spacers only makes the job more risky.  One member here claims he almost lost an eye when that job did not go exactly right.  Even with a face-shield, the risks seem needless, in very real terms.  Cheers,
Red

Red, this a common reaction to something you're not expecting. You would be surprised how little force there actually is on the fork caps after you've done them once or twice.
As Randy says, if the front wheel is elevated, the force is not that great, palm of you hand is all that's required. It aways seems worse when you're not expecting it.

Whoever you quoted as nearly taking their eye out clearly got caught off guard not expecting anything, which makes it seem much worse. This also happens with cam chain tensioner bolts and m/c circlips. I'd like a dollar for every guy that's had the innards of his master cylinder fly across the garage when they remove the circlip, not realising it was under pressure.

Next time you undo them you will now know exactly what to expect and anticipate it, no surprises, no missing eye balls.

You are talking to an audience here that has collectively done thousands of forks, Randy and myself would have literally done hundreds, keep it simple and weigh up just how often you need to do this against the work involved in the mod you are proposing.

Randy has taken the time to diplomatically responded to your suggestion but you're making a mountain out of a mole hill.

Noel

[chiz]

HI
I just want to point out something about what Randy said on short and long damper rods, The shorter the rods the shorter the forks will be but with less travel. So if you are looking for a shorter fork for a project it may not be necessary to do anything further than to shorten the rods to the overall length you want to shorten your forks.
Chiz

[skik]

150 mm as per Yamaha. Race Tech and some others say, you can go as high as 130 mm. That is springs out and fully compressed.
Kurt

Okay, I guess, but what I really want to know is the actual fork oil level, measured on the outside of the fork in some reliable way, when the bike is on the center stand.  I want to be able to drain the forks, and replace the fork oil, without any dis-assembly of the forks.  I would drill a hole in each fork at that correct oil level, weld a nut over the hole, and insert a tube to add the fresh oil.  Then remove the tube, install a screw into the nut, to seal the hole again, until the next fork-oil change.  The sealing screw would be short; it would not intrude into the fork interior.  Yeah, I know, this method probably makes 'way too much sense.     

Does anybody have the actual fork oil level measurement, forks fully extended, but otherwise ready to ride?

Thanks,
Red

WHAT!like WHAT!! are you for real

[simi_ed]

150 mm as per Yamaha. Race Tech and some others say, you can go as high as 130 mm. That is springs out and fully compressed.
Kurt

Okay, I guess, but what I really want to know is the actual fork oil level, measured on the outside of the fork in some reliable way, when the bike is on the center stand.  I want to be able to drain the forks, and replace the fork oil, without any dis-assembly of the forks.  I would drill a hole in each fork at that correct oil level, weld a nut over the hole, and insert a tube to add the fresh oil.  Then remove the tube, install a screw into the nut, to seal the hole again, until the next fork-oil change.  The sealing screw would be short; it would not intrude into the fork interior.  Yeah, I know, this method probably makes 'way too much sense.     

Does anybody have the actual fork oil level measurement, forks fully extended, but otherwise ready to ride?

Thanks,
Red

Red,  ihave a question for you:  If you went ahead with this ill-advised idea and then had a fork seal fail, how would you go about replacing it?  The seal is slid down the OD of the tube after fork assembly.  Just a thought.