Author Topic: Questions about fork seals on a '78 CB750F (Read 7409 times)

michrobi · « **on:** June 10, 2009, 08:24:05 PM »

I drained and took my forks off today to change out the seals...

The Clymer manual seems pretty clear with the instructions (for an early k at least, same as the popular "how to" page linked all over our forums here, which is awesome - but not my bike).

What I'm worried about are the springs in the forks, and how best to remove those top cap bolts without hurting myself, the fork or anything in the shop. I also don't have any spare broomsticks around to jam in there. Is that something I'm going to have to do, or is it optional?

Anything else I should know about these 78 F's before I get going on it?

Johnie · « **Reply #1 on:** June 10, 2009, 08:31:25 PM »

Before you remove the caps try to loosen that allen bolt on the bottom. You may not even need a broomstick. As far as the caps go, I use a T handle with the socket. That way I can put even pressure on the cap as I unscrew it. Never had a problem. As long as you are aware of the spring you will be OK. It will not come flying out like those trick peanut cans...

michrobi · « **Reply #2 on:** June 10, 2009, 09:28:43 PM »

After some coaxing, those allens came loose. Thanks for the tip Johnie.

In order to loosen up those top cap bolts, I guess I'll need either a vise or a rubber clamp pipe wrench. That sound about right?

mick750F · « **Reply #3 on:** June 10, 2009, 09:36:33 PM »

Quote from: michrobi on June 10, 2009, 09:28:43 PM

In order to loosen up those top cap bolts, I guess I'll need either a vise or a rubber clamp pipe wrench. That sound about right?

It's easiest to remove the caps when the forks are still mounted. You could always pop them back into the "clamps" they came out of.

Mike

michrobi · « **Reply #4 on:** June 10, 2009, 09:58:19 PM »

oh yeah, duh!

michrobi · « **Reply #5 on:** June 11, 2009, 03:57:19 PM »

These fork seals haven't been changed for 20 years. I'm doing the best I can to get a grip on it with some needle nose pliers, but I'll be damned if I can get the seal to budge. I soaked it in hot water for several minutes till it was varying degrees of warm, but the seal isn't budging no matter how warm the shock is. Is there a tool that gets under the seal without damaging the sidewalls? What am I doing wrong?

noahspop · « **Reply #6 on:** June 11, 2009, 04:24:53 PM »

i have a leaky left one.
i'll be changing my soon.

does anbody know if there is anything wrong with the seals they sell on ebay for around $12.00?

i look forward on the outcome of your endevor.
i was told you didn't have to take the forks off of the bike.
anyways good luck

Johnie · « **Reply #7 on:** June 11, 2009, 04:50:42 PM »

Quote from: michrobi on June 11, 2009, 03:57:19 PM

These fork seals haven't been changed for 20 years. I'm doing the best I can to get a grip on it with some needle nose pliers, but I'll be damned if I can get the seal to budge. I soaked it in hot water for several minutes till it was varying degrees of warm, but the seal isn't budging no matter how warm the shock is. Is there a tool that gets under the seal without damaging the sidewalls? What am I doing wrong?

I used a screwwdriver with protection on the top edge. Do not let the driver hit the side wall. Pry it out using the top of the fork tube for leverage. I have seen a tool you could buy at places like AutoZone. Keep at it...let us know how it goes.

Johnie · « **Reply #8 on:** June 11, 2009, 04:52:28 PM »

Quote from: noahspop on June 11, 2009, 04:24:53 PM

i have a leaky left one.
i'll be changing my soon.

does anbody know if there is anything wrong with the seals they sell on ebay for around $12.00?

i look forward on the outcome of your endevor.
i was told you didn't have to take the forks off of the bike.
anyways good luck

I have seen it time and time again on this board. Aftermarket seals just do not compare to the OEM. Go with the OEM if you can at all swing it.

Toxic · « **Reply #9 on:** June 11, 2009, 05:25:42 PM »

leave in boiling water for 4 min.

Mine were the most stuck that I have ever encountered. They came out with some serious effort after the water treatment.

Before soaking in the hot water there is no way they were coming out.

michrobi · « **Reply #10 on:** June 11, 2009, 06:05:42 PM »

I got em out with a Harbor Freight bearing puller http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=4876

I had to trim the bottom half of the inner rubber wall off the bearing so the teeth on that thing could get under the metal, but with a little adjusting here and there I won.

Now it's time to douche all the parts and reassemble, I'll get shots.

michrobi · « **Reply #11 on:** June 11, 2009, 09:20:29 PM »

After getting the seals out, the rest was a breeze...

Here is a closer shot of the old seals, and the lower half of the inner rubber that I had to trim off in order to get the teeth of the puller under it.

Here are the shocks with the seals just having come out, and ready for cleaning.

Cleaned all the parts, piston, springs and pressure cap for each fork, then used the old seal to mallet in the new ones. Once done I assembled the forks without the top cap bolts, leaving the springs in the forks visible.

Now with two perfectly cleaned and sealed forks, I reinstalled them on the bike and poured 6.4 oz. of 15w Fork Oil in the open top and bolted the caps on. This pic is a little dark, don't know if you can see my funnel or not.

Back from a short test ride, felt good but it's raining so I couldn't really get on the brakes.

Saved myself 200 bones and my weekend by doing it myself. And I know exactly what condition every part of my forks are in (better than I thought). Win!

Bido · « **Reply #12 on:** June 12, 2009, 05:38:14 AM »

Way to go nothing like doing it yourself and knowing it was done right!!!

Bido

Johnie · « **Reply #13 on:** June 12, 2009, 07:09:13 AM »

Good for you. Now you will be able to answer questions for others on the fork rebuild. The only other thing I did when I had mine off was to remove the old clearcoat and polish them up.

michrobi · « **Reply #14 on:** June 12, 2009, 09:17:31 AM »

I found a little fork oil under my left fork this morning. The oil plug is dry as a bone, the oil looks like its coming from the allen bolt under the fork. When I took those allens out, they both had some gluey substance around the threads that I had to peal off. Like someone put a little thin rubber sheath on the bolts. It was probably a silicone of some kind. Should I take those back out and put some Teflon on the threads?

MCRider · « **Reply #15 on:** June 12, 2009, 09:25:26 AM »

Quote from: michrobi on June 12, 2009, 09:17:31 AM

I found a little fork oil under my left fork this morning. The oil plug is dry as a bone, the oil looks like its coming from the allen bolt under the fork. When I took those allens out, they both had some gluey substance around the threads that I had to peal off. Like someone put a little thin rubber sheath on the bolts. It was probably a silicone of some kind. Should I take those back out and put some Teflon on the threads?

I'm fairly certain they take a copper O Ring sealing washer. They need to be tight, so rubber and/or silicone won't do it. I'll go check a fiche.

Yup 90544-283-000 @ $1.60 ea from hondaparts-direct (usually lowest price) they must be something special.

Teflon or the like may get it done, but you'll know what you really need. Probably a good sealing washer from the hardware would work.

michrobi · « **Reply #16 on:** June 12, 2009, 09:51:49 AM »

Heya Ron,

The copper washers survived, and I reused them. maybe I just didn't give it the torque it needed. I'll report back after I get the wheel back off tonight.

Johnie · « **Reply #17 on:** June 12, 2009, 09:53:50 AM »

Agreed...there should be a copper washer on each allen bolt. There was on my KO & K1. I also put a little blue Locktite on the threads as one of my later bikes suggests that too.

MCRider · « **Reply #18 on:** June 12, 2009, 09:55:00 AM »

Quote from: michrobi on June 12, 2009, 09:51:49 AM

Heya Ron,

The copper washers survived, and I reused them. maybe I just didn't give it the torque it needed. I'll report back after I get the wheel back off tonight.

Hello:
The washers may be shot. If they are doing their job, no need for chemicals. Give it a skosh more torque. They screw into steel (bottom of dampener) but I'd hate to strip one.

754 · « **Reply #19 on:** June 12, 2009, 10:05:19 AM »

You should ANNEAL the copper washers.

get a bit of oil in small cup, hang the washers on a wire, so they cant fall off, but not touching each other. Then heat with a propane torch till red, then quench in oil, moving them around as you do so.

Now, they are ready to use..

MCRider · « **Reply #20 on:** June 12, 2009, 10:14:48 AM »

Quote from: 754 on June 12, 2009, 10:05:19 AM

You should ANNEAL the copper washers.

get a bit of oil in small cup, hang the washers on a wire, so they cant fall off, but not touching each other. Then heat with a propane torch till red, then quench in oil, moving them around as you do so.

Now, they are ready to use..

Oh you're so old fashioned.

No one anneals anything anymore.

I remember doing that to the copper washers on my Triumph Bonneville. We thought we were so hot.

Kidding aside. you are correct.

michrobi · « **Reply #21 on:** June 12, 2009, 10:54:04 AM »

Well, I decided not to wait till tonight since today is the only dry day we're going to have for the next 10. Looks like that left allen wasn't as snug as I thought. I gave it a skosh plus one R.C.H. Got a quarter turn with my 4 inch allen, so I'm pretty confident it just needed tightening. I'm not the biggest fan putting #$%* on oil sealing threads ever had, so I hope that'll do er.

Thanks for the tips fellas.

MCRider · « **Reply #22 on:** June 12, 2009, 10:58:51 AM »

Good.

OK I'll bite, what R.C.H.?

michrobi · « **Reply #23 on:** June 12, 2009, 11:10:08 AM »

hahaha gotcha!

R = Red
C = Starts with C and rhymes with Hunt
H = Hair

michrobi · « **Reply #24 on:** June 12, 2009, 11:21:58 AM »

It's rude and crass, I know. But you don't say the words, just "are cee atche" and that means the littlest bit possible. It was a common technical term in the Ironwork business, I swear!

MCRider · « **Reply #25 on:** June 12, 2009, 11:40:14 AM »

Oh I have one of those in my micrometer drawer.

nobrake · « **Reply #26 on:** June 12, 2009, 01:20:21 PM »

Quote from: 754 on June 12, 2009, 10:05:19 AM

You should ANNEAL the copper washers.

Huh? This technique before MJ got surgeries or after?
Enlighten us please.

MCRider · « **Reply #27 on:** June 12, 2009, 03:49:25 PM »

Quote from: nobrake on June 12, 2009, 01:20:21 PM

Quote from: 754 on June 12, 2009, 10:05:19 AM
You should ANNEAL the copper washers.

Huh? This technique before MJ got surgeries or after?
Enlighten us please.

It is as he says. You can refresh a used up copperwasher with the annealing process. Was done quite regularly back when mechanics actually did something rather than just R&R.

754 · « **Reply #28 on:** June 14, 2009, 10:03:20 AM »

Basically takes the crushed somewhat workhardened copper washer, back to its original, dead soft state.

gives it a new chance to do its job..

there is a few things about bike wrenching that are sorta cool.

watching the washers turn red, then the puff of smoke when you quench is one.

another is when you are pressing apart a crank, and the press loads up and then BANG

, the pin moves.. I know a bike tech that used to use my press to assemble/disassemble cranks, showed me the scribing tricks and more. I swear that guy probably got more enjoyment out of hearing the pin pop& jump, than almost anything else in life...

another is straightening a fork, leaving it in the blocks with dial indicator on it, then telling the customer to find 3 thou runout in it..

HavocTurbo · « **Reply #29 on:** June 14, 2009, 10:38:47 AM »

My favorite is watching customers jump when the bead seats on a mag rim.

754 · « **Reply #30 on:** June 14, 2009, 10:52:25 AM »

Cleaning off the rim with schotchbrite or steel wool helps, and R-Glyde...

but yeah they sure do snap sometimes.. I wouldnt want to go much over 60lbs on one either.

do you remove the valve stem, to get max air in quickly, it helps.

HavocTurbo · « **Reply #31 on:** June 14, 2009, 11:39:24 AM »

Quote from: 754 on June 14, 2009, 10:52:25 AM

Cleaning off the rim with schotchbrite or steel wool helps, and R-Glyde...

but yeah they sure do snap sometimes.. I wouldnt want to go much over 60lbs on one either.

do you remove the valve stem, to get max air in quickly, it helps.

I use the green biscuits on an angle drill or angle die grinder. Seems to work ok if you aren't too forceful.

Standard dishsoap and water acts as double duty for lube and leak detect.

Oh you should always pull the valve stem out. Makes a louder pop that way.

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Author Topic: Questions about fork seals on a '78 CB750F (Read 7409 times)