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Fork Oil - capacity's & type

WhiteWidow

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Having issues when braking, I feel a CHUG/VOID in compression of fork when braking.

Looking @ the factory specs. I noticed oil type is not shown.

I've heard that heavy viscosity automotive oils can be used.

I've also noticed on this chart that the amount of oil varies from assembly to changing.

5.2 oz. Changing.
5.8 - 6.0 oz. Assembly

I'm looking for a firm feel when braking and taking bumps.

Any experience or knowledge with FORK OIL would be greatly appreciated.
 

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Having issues when braking, I feel a CHUG/VOID in compression of fork when braking.

Looking @ the factory specs. I noticed oil type is not shown.

I've heard that heavy viscosity automotive oils can be used.

I've also noticed on this chart that the amount of oil varies from assembly to changing.

5.2 oz. Changing.
5.8 - 6.0 oz. Assembly

I'm looking for a firm feel when braking and taking bumps.

Any experience or knowledge with FORK OIL would be greatly appreciated.
Hi,

Oil amount varies as you state, because you cannot get oil the oil out when just changing the oil. So a full fork strip required more oil as you remove the full amount.

I was lucky enough to track down two old stock, but new, front fork legs for my 1979 CB750KZ last year. But when I fitted them they were very stiff. So much so that after a couple of hours riding, the front end was almost solid. The fork legs came primed with the original oil and quantity from the factory, so I assumed that it was my fork alignment that was wrong. After spending hours trying everything, I went back to the drawing board and thought about the oil that came with the forks.
I bit the bullet, removed the forks legs again and changed out the original red Honda oil for off the shelf ATF (auto transmission fluid) oil with the quantity specified in the Honda manual. Riding was much the same but possibly a little softer.

So I dropped a measured quantity from each leg via the fork leg drain bolts (careful here, support the weight of the bike front end or you will lose a lot of oil !) and tried again. This made all the difference and the front forks are now performing brilliantly. So, I assume that the spec. quantity can be a little too much and that it may just pay you to trial and error oil/quantity.

Don't know where you heard that heavier oils are ok, because Honda actually state in the manual that ATF should be used. ATF oil is generally around 0w/5 or 5w/10. I think I ended up with 0w/7.5.

Hope this helps,
 
Thanks for the great info.
I'm pulling the front wheel off this weekend so I can turn forks backwards to expose drain plugs.
Going to floor jack the frame then rest forks on a plastic tub.
I will use the proper oil and fill as indicated in manual.
Test drive and make adjustments as needed.
You gave some great tips.
Enjoy the ongoing riding season.
 
The drain screws normally face outwards away from the wheel ? You should be able to access them when the bike is ready to ride ? If you can be bothered, I would simply removed the fork tubes and empty them completely. That way you know exactly what is inside them both and have a clean start. If you have gone that far it might be as well to remove the top cap hex plugs ( loosen before you loosen the fork yoke top and bottom clamps) then you can remove the hex plugs and invert the fork to pour out all of the old oil. Do you have a manual for the correct yoke tightening procedure ? Also, put a bit of tape on the fork stantions (not the alloy fork sliders) and mark the fork fronts, just in case they are not perfectly straight, then you can get them as they are now. BTW, are the stantion tubes straight ? If not this can affect fork performance greatly. Do not mix up the parts on each leg. They must go back as they are now. Best of luck.
 
First image attached is your original image with the drain screw marked in the red circle. There are also three pages from a Haynes manual that might help. If the fork seals are not leaking I would not try to remove them. They can be a real pain and give you even more problems than you started with. Protect your fuel tank before loosening the handlebar clamps (so that you can loosen the hex head top caps) if you decide to unscrew to empty the fork legs.

I have included below three procedures below that I found online that may help with fork alignment. Not my words but one of them may help.

Be very careful if you jack the front end of bike at any time. Think before action !



Forks could be suffering from Stiction... try this.

Method 1

Loosen the front fork hex caps, and then pump the forks with the brake on. That will center the wheel in the forks, if it is out of alignment. Then tighten the fork caps. Then, your triple trees (yokes) can be done, loosen the upper right pinch bolt and lower left, pump the forks again, (re-tighten the bolts) then do the lower right and upper left to take out any misalignment in the trees. Remember to tighten the first two bolts before loosening then other two, or your forks will slip up into your trees... There may be a method to do this in the SOHC manual, also.

Method 2

Start by jacking the bike up so the front wheel is off the ground; a half-inch or so will do it.

If the forks have been removed from the bike:

**1 **Set the stantion tube fork height level with the top of the the upper clamp, and then tighten the pinch bolts in stages to the proper torque. If you're not convinced that the heights are equal, slip the axle into place. If it doesn't glide smoothly through the forks, one leg is higher than the other, so readjust them until the axle slides through them with little or no effort.

2 Install the front fender-but don't tighten the bolts.

3 Install the front wheel and axle. If the axle threads into the fork, thread it in loosely; if it uses a nut, just snug the nut down by hand. Do not tighten the axle pinch bolts.

4 Spin the wheel as vigorously as you can and abruptly clamp on the brake. Holding the brake lever on, tighten the front axle

**5 **Lower the bike onto the ground, and, while holding the front brake, gently pump the forks a few times. You did remember to tighten those upper pinch bolts didn't you?

6 Tighten the lower clamp's pinch bolts, followed by the axle pinch bolts.

7 Tighten the fender bolts.

That's it bub, the forks are now aligned, but wait: there's more.

If you suspect the forks are tweaked but don't want to go through the whole shebang, there's a short cut.

Support the weight of the bike on the jack or center stand, and loosen the front axle. Remove the lock nut, and then try to slide the axle out of the fork. If it comes away with little effort, the forks are in alignment. If the axle has to be pounded out, it's a safe bet the forks are slightly tweaked. Of course that presumes the axle hasn't been rusted into place.

To correct a slight misalignment, loosen everything but the top clamp pinch bolts (you don't have to remove anything), and start at Step #3. Anytime the wheel is removed, perform steps #4 and #5: that'll center the wheel in the fork and provide better suspension and braking action.


Method 3

Here’s how to remedy. Keep in mind that the sequence and order of this procedure is very critical:

1. Start with the bike on a level concrete floor on the centerstand. Put a small floor jack under the front of the engine (with a very thin board to protect the engine). Jack up the bike just enough so that the weight is off the front tire. Warning: jacking beyond the point that the rear tire contacts the ground will lever the bike off the centerstand and cause a nasty spill.

2. For extra safety, run 2 tie-down straps down from the ceiling to the handlebars.

3. Loosen all of the following in this order but do not remove:

• Left side, front axle cap pinch nuts (left as viewed by the rider). There are 4 of these. Make sure you’ve loosened these 4 nuts enough so that pressure is off the retainer and the left fork lower (“slider”) is free to “float” relative to the axle. Test to make sure the slider can move side-to-side relative to the axle.

• All 6 of the bolts that secure the fender

• Top fork stanchion Allen bolts (secure the fork tubes to the upper triple clamp).

• Fork caps (just loosen slightly)

• Lower fork stanchion attach bolts (secure the fork tubes to the lower triple clamp).

4. Next, remove the fork caps to relieve the pressure from the fork springs.

5. Carefully lower the front of the bike with the jack until the fork is fully compressed. Be sure you have enough slack in the safety tie-downs to allow full compression. As the front end is lowered, carefully observe the action of the brake hoses and speedo cable to make sure they are not put into jeopardy by this extreme compression.

6. Tap the lower and upper triple clamps (stanchions) in several spots with a soft mallet.

7. Carefully tighten all of the fasteners in the following order. Very important: be sure the fork tubes are at the same relative height inside the triple clamps. Normally, they should be flush with the top of the upper triple clamp.

• Lower triple clamp pinch bolts

• Top triple clamp pinch bolts

• Left side axle pinch nuts

• Fender attach bolts.

8. This is a good time to make sure your fork oil is at the correct level. With the fork fully compressed and the fork springs removed, I run 160mm of free air space above the oil. This is a more accurate level of filling the forks than the factory suggests in the manual. Their method is approximately 6 oz when you drain the forks… 6.8 oz when you do a complete overhaul.

9. Raise the bike and replace the front springs. Loosen the top triple clamp pinch bolts again to reinsert and tighten the fork caps. Re-tighten the top pinch bolts.
 

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Again, this is amazing detail regarding my problem.

I have a complete understanding of the teaching I've received.

There are factors here that haven't been considered.

This is all master mechanic technics and resolutions to my specific issue.

So very useful, greatly appreciated.
 
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