Author Topic: 72 vs 76 CB500/550 forks??? (Read 8187 times)

puppytrax · « **on:** July 01, 2006, 05:31:10 AM »

My CB500 has a set of forks with very rusty top bolts; the alum lowers are fair...I also have a set of 76 550 forks with good top bolts but poor looking lowers...

The top bolts don't interchange; the forks are quite different internally, but the entire legs will interchange (as far as I can see...just unclamp the tubes and change legs as a unit - not changing the triple trees)...

The 72 top bolts are no longer available...

and to put the 76 fork legs on, I'd want to clean [buff] the lowers...a lengthy job...

So...my question is, is there any other advantage to swapping over to the later fork legs??? They look the same, the wheel/brakes/fender will fit, but am I gaining anything besides a little bit of chrome at the top of the forks???

jsaab2748 · « **Reply #1 on:** July 01, 2006, 07:01:07 AM »

If the later forks are from a K model, look on the inside of the lower cases and see if they say "341" on them. If so, they're the same lower cases that came on the 750 K2 (?)-6.
You then have the advantage of using the front brakes from a 750 should you desire, which are bigger rotor and caliper. I think dimensionally the fork assys. from the 500 are the same externally as the later 550, and will interchange?

puppytrax · « **Reply #2 on:** July 01, 2006, 10:47:32 AM »

Quote from: jsaab2748 on July 01, 2006, 07:01:07 AM

If the later forks are from a K model, look on the inside of the lower cases and see if they say "341" on them. If so, they're the same lower cases that came on the 750 K2 (?)-6.
You then have the advantage of using the front brakes from a 750 should you desire, which are bigger rotor and caliper. I think dimensionally the fork assys. from the 500 are the same externally as the later 550, and will interchange?

Hmmmm...Why yes, they are "341" forks...and they're mirror images of each other...so they're adaptable to twin disks/calipers (there are caliper mounts on both lowers)...although the 550 only had a single disk on it...

Interesting...but not anything particularly desirable (to me, at least)...

Thanks for the info! Maybe I can pawn them off...

TwoTired · « **Reply #3 on:** July 01, 2006, 10:52:32 AM »

I don't have much experience with the Cb500 forks. I assume Honda made some improvemens to them when the design changed in 1974.

They do swap as assemblies between the bikes. Important to note that the volume of fluid changed WRT design.

Cheers,

puppytrax · « **Reply #4 on:** July 01, 2006, 11:04:38 AM »

Quote from: TwoTired on July 01, 2006, 10:52:32 AM

They do swap as assemblies between the bikes. Important to note that the volume of fluid changed WRT design.

I'm a simple lad...backwoods born and raised...limited vocabulary...can't read much...

WTF's WRT???

TwoTired · « **Reply #5 on:** July 01, 2006, 11:12:23 AM »

With Regard To

puppytrax · « **Reply #6 on:** July 01, 2006, 11:21:27 AM »

Quote from: TwoTired on July 01, 2006, 11:12:23 AM

With Regard To

Thank You!

bryanj · « **Reply #7 on:** July 02, 2006, 04:52:33 AM »

Only difference 500 to 550 is that "mirror image" slider and the internals. You could swop the two alloy 500 sliders onto the 550 legs by undoing the allen bolts up under the bottom, Do change the fork seals while you have them appart. The only difference on the top nuts is that the 500 has a threaded hole for the damper rod to screw into which you could easily drill and tap yourself if you want to go that way. Somewhere i have some NOS old 500 top nuts-----the important word is somewhere!!!!

puppytrax · « **Reply #8 on:** July 02, 2006, 05:16:31 AM »

Quote from: bryanj on July 02, 2006, 04:52:33 AM

The only difference on the top nuts is that the 500 has a threaded hole for the damper rod to screw into which you could easily drill and tap yourself if you want to go that way. Somewhere i have some NOS old 500 top nuts-----the important word is somewhere!!!!

As far as I can see, I could just change the entire leg, lowers & all. But I'd have to do something about the lowers - they look bad.

Those NOS top nuts are listed at ~$17+ ea in the Fiche...I'd gladly pay that for a new set...

The 550 top nuts can't be easily drilled & tapped because they are hollow...I had thought of threading them for a 3/8NPT steel plug, and threading that for the rods, but wouldn't you know, all I can find locally is cast iron pipe plugs...

Edit: The top nuts [short stubby bolts, really] actually are different...slightly longer (about 1/4"), more of an unthreaded portion above the o-ring; and different size spanner required for the top "nut"...

Having said all that, I tried one in my 500...fits OK; the o-ring seals; and the bolt threads all the way down. Looks good enough for a gov't job to me...

...if I can just find some steel pipe plugs around here...

puppytrax · « **Reply #9 on:** July 09, 2006, 03:51:30 PM »

Quote from: bryanj on July 02, 2006, 04:52:33 AM

Only difference 500 to 550 is that "mirror image" slider and the internals. You could swop the two alloy 500 sliders onto the 550 legs by undoing the allen bolts up under the bottom, Do change the fork seals while you have them appart. The only difference on the top nuts is that the 500 has a threaded hole for the damper rod to screw into which you could easily drill and tap yourself if you want to go that way. Somewhere i have some NOS old 500 top nuts-----the important word is somewhere!!!!

Bryan -

You have gotten me thinking...(

)...Can the 72 CB500 aluminum lowers be swapped with the 76 CB550 lowers?? I don't need the dual-disk fittings, and just tried to buff the 550 lowers with white rouge...didn't work...

I'm thinking if i swap all the internals it should work...the seals are the same...and I could run the nice little short 550 dust boots instead of the long accordian dust covers...I think...

bryanj · « **Reply #10 on:** July 10, 2006, 06:52:55 AM »

Dont need to swap the internals----just the alloy lowers and those small"dust" caps are a cb500 twin part

puppytrax · « **Reply #11 on:** July 10, 2006, 06:59:45 AM »

I know; I wasn't clear...I'd like to change over to the 76 forks internals, with my 72 lowers...less parts, and no long rod threaded into the top nut...It looks like if I undid that Allen bolt in the bottom, everything will come out...of course, the steel circlips in the top of the lower are pretty well rusted in place...

The 78 CB550 also lists those small dust covers as well...but of course I'd want chromed tubes...mine are rusty under the accordian boots...Ka-Ching!!!

puppytrax · « **Reply #12 on:** July 10, 2006, 08:58:48 AM »

I checked the Hoda Fiche; the 76 lowers have a different part # than the 72...either leg...

I took one of the 76 legs apart...not too difficult...needs new seals of course...and the tube is rusty...looks like it *might* fit in a 72 lower... $:-\$

I'll have to check around here; see if I can find anyone who polishes aluminum...or someone who knows what rouge to use on aluminum and do it myself...

I sent an email to Forking By Frank on new tubes...no reply yet...

puppytrax · « **Reply #13 on:** July 22, 2006, 03:39:34 AM »

Quote from: TwoTired on July 01, 2006, 10:52:32 AM

I don't have much experience with the Cb500 forks. I assume Honda made some improvemens to them when the design changed in 1974.

They do swap as assemblies between the bikes. Important to note that the volume of fluid changed WRT design.

Cheers,

TwoTired, if you're still following this...My CB500 forks hold 5.5oz of 10w30 motor oil (as specified in the CB500 Honda shop manual); the CB550 calls for 5.5oz of ATF (Honda CB550 shop manual)...

So, as far as I can tell, the spec for the oil changed, but not the volume...

But I'd be curious to know what led you to say the fluid volume changed...

TwoTired · « **Reply #14 on:** July 22, 2006, 09:46:46 AM »

1972 CB500 owners manual pg 73 ; 5.4 oz. (160 cc) ATF. Oil change not dry assembly.
1974 CB550 owners manual pg 76 ; 5.4~5.6 oz. (160~166 cc) ATF. Oil change not dry assembly.
1977 CB550F owners manual pg 74 ; 4.8~4.9 oz. (145~150 cc) ATF. Oil change not dry assembly.

Honda Shop Manual Pg 81 : 5.3~5.6 oz (155~165 cc) Honda ATF (at dissassembly) /CB500/
Honda Shop Manual Pg 135 : 5.4 oz (160 cc) /CB500/
Honda Shop Manual Pg 137 : 6.3~6.5 oz (185~191 cc) Presumably the Cb550 Supplement to the shop manual, added for 1974.
Honda Shop Manual Pg 157 : 5.6~5.8 oz (165~170 cc) Honda ATF, The Cb550F Supplement to the shop manual, added for 1975.
Shop manual doesn't list a fork oil capacity change for the K3 and F2 models. But, my owners manual does.

From my observations, there are three fork designs.
1) Cb500 71-73
2) Cb550 74-76 including F and K models
3) 77-78K and 77F models

I think the shop manual data on pg 137 is likely a misprint.

Cheers,

puppytrax · « **Reply #15 on:** July 22, 2006, 03:57:54 PM »

Well, my scanner bulb is failing [or so it says] but this is what my 72 Owners Manual says -

pg 73; #2 G "Move the fork springs to one side and pour 4.6 - 4.9ozs (135-145 cc) of premium quality ATF (automatic transmission fluid) into each fork leg."

And from my CB500 Service Manual -

pg 87 C 7 - "Fill the fork bottom case with 160 cc (5.4 ozs) SAE 10 W-30 grade oil through the fork top bolt hole."

I personally don't think American Honda cares what you put in it as long as it's oil...

TwoTired · « **Reply #16 on:** July 22, 2006, 07:09:35 PM »

Jeez, you suppose we have to have to note revision history, too?

Cb500 K1 owners manual 313232 or C4000703 Printed 1971

Shop manual date of isue July 20, 1977. 6137407

FWIW

Cheers,

puppytrax · « **Reply #17 on:** July 22, 2006, 07:17:18 PM »

Quote from: TwoTired on July 22, 2006, 07:09:35 PM

Jeez, you suppose we have to have to note revision history, too?

Cb500 K1 owners manual 313232 or C4000703 Printed 1971

My Owners Manual [from under seat] is -

CB500 K2 Owners Manual 3132301 or B5000712 Printed 1972

My Service Manual is -

623231 or A2000612 printed 1971

puppytrax · « **Reply #18 on:** July 23, 2006, 06:47:11 AM »

TwoTired - Got a new scanner, up & working...I'm not impressed with it [HP 7210 USB MFP], but it seems to work...here's what I mentioned up above...

TwoTired · « **Reply #19 on:** July 23, 2006, 11:04:59 AM »

Not that it matters for the oil quantity topic. But, you are aware that the K2 Cb500 is a 73 model, right?
American CB500 Model years were 71, 72, and 73, with K0, K1, K2 designations. Do you have the 3 1/2 or 3 inch gauge dials?
Info source:
Honda Motorcycle Identification Guide 1988 American Honda Motor Co., In.

I don't have a scanner. Guess you'll have to trust I'm not pulling numbers out of my butt. $:-\$ Though I could use my camera, I suppose.

Here's some more data from Non-Honda sources:

Haynes manual printed 1976 for CB400-Cb550 1973 on:
Front Fork Capacity 155-165cc (5.3-5.8 oz)
Refill after draining 140-145cc (4.7-4.8 oz)

Chilton ; Honda Fours printed 1974
SAE 10-30W oil or ATF:
500, 550 - 5.4 oz (160 cc)

Clymer ; Honda Service - Repair Handbook printed 1975
SAE 10-30W oil :
500, 550 - 5.4 oz (160 cc)

I don't like the idea of using motor oil, as it can foam up when agitated in forks. I've used ATF (it has anti foaming qualities). But, I generally like a higher viscosity oil. So, I use either 10 or 15 W Fork oil. I remember the quantity also had an effect on firmness.

Cheers,

P.S. I picked up the carb gaskets sets Friday. But, I'm going wait for the garage temps to go down below 100 before I rebuild those carbs.

puppytrax · « **Reply #20 on:** July 23, 2006, 01:24:31 PM »

Quote from: TwoTired on July 23, 2006, 11:04:59 AM

Not that it matters for the oil quantity topic. But, you are aware that the K2 Cb500 is a 73 model, right?

Well, my CB500 is titled as a 73, but the VIN plate says 1972...so I go by that...

I've been meaning to ask what everyone goes by when they order parts...if the VIN plate isn't the correct year, then I'll go with the title year...

Quote

Do you have the 3 1/2 or 3 inch gauge dials?

I gots the 3 1/2" dials.

Quote

I don't like the idea of using motor oil, as it can foam up when agitated in forks. I've used ATF (it has anti foaming qualities). But, I generally like a higher viscosity oil. So, I use either 10 or 15 W Fork oil. I remember the quantity also had an effect on firmness.

I'll see what my local Honda dealer has for fork oil. 10W fork oil seems like a good starting point.

Quote

P.S. I picked up the carb gaskets sets Friday. But, I'm going wait for the garage temps to go down below 100 before I rebuild those carbs.

That's cool! Thanks! How'd the 087A's turn out?? (Or was it the 022A's?? I can't remember...I've looked at so many, I don't even know what I have any more...)

TwoTired · « **Reply #21 on:** July 23, 2006, 03:14:42 PM »

Back then, the model years started about september of the previous year. Plus they came over on slow boat from Japan. It is quite common to have a japan manufacture date earlier than the model year.

When you go to order parts for it, rest assured you have a 73 K2. Big dials were introduced that year.

087A and 627B carbs
I decided to measure all the internal parts of both sets of carbs while rebuilding them both. So, I've been waiting for the kits to come in before the effort... When it gets a bit cooler.

Cheers,

bryanj · « **Reply #22 on:** July 24, 2006, 08:30:34 AM »

Parts that change will change from a specific Frame (vin) number and be irrelevant of year, same with engine parts. Fork oil has improved phenomenally over the years and it is now best to use a "specific" fork oil as against the engine or ATF. ATF was speced to stop the foaming of engine but both are not as good as the proper fork oils.On the 500/550 all the sliders will fit all the steel legs, and, once you get away from the very early long rod up the middle, the internals will swop The big thing is to make sure you are using "pairs" of items from one bike to keep the damping similar though having said that i bought a pair of NOS complete legs for a 550 from Dave Silver for £70 each (complete with top nuts and concertina boots) and will put a NOS RH 500 slider on the one to get a "pair" of 500 ones!

canttuckmyshirt · « **Reply #23 on:** February 13, 2008, 02:00:03 PM »

I'm SO SO So So so sorry to bump this OLLLD thread up. Just want to clarify something.

Can I swap the lowers from a Cb550 onto Cb500 fork legs? No other changes? I'm having a hard time wrapping my head around this.

bryanj · « **Reply #24 on:** February 14, 2008, 12:00:20 AM »

Simple answer YES---Just undo the allen bolts that go upwards and slide em off---Ideal time to change seals though

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Author Topic: 72 vs 76 CB500/550 forks??? (Read 8187 times)

jsaab2748