Topic: CB750 Clutch Spring Discrepancy....what gives?

[fatcaaat]

People on the forum and the manual have found different information relative to clutch spring.

Some say the size from factory is 31.94mm and Servicable Limit is 30.5mm

Some have pulled them from the basket and they are 35.5mm long.  that is 3.5mm different from what the manual says.  There is no way they could get longer, so what gives? 

What is the correct length?  Why are there differences. 

My 1976 CB750K when pulled were 35.5mm long.  Doing a search I find people to have them similiar.  Some also have them at 31mm.  What gives?

[scondon]

  The clutch pack changed after the K4 model as did the spring. There are at least three different springs available for 69-78 CB750's. It may be wise to consult a manual for your specific model before determining stock wear length.

[Tower]

I thought that,
- K0 through K7, and F1 all used the same clutch return springs, 31.9 -30.5 mm
- F2 used the 39.6 - 36.8mm springs with stiffer rating (242 lbs from 220 lbs)
- Model A has a single large return spring, 39 - 36 mm

In what model did the 35.5 mm springs appear?  Anyone have a fiche with contradictory specs?

[fatcaaat]

Well, the manual says for all 69-78 they are supposed to be about 31.9.  That is certainly not the case, unless there is a supplement somewhere I don't see. 

Isn't that going to throw things off when people upgrade their clutches?  If you look at the VESRAH, they tag 75-78 with the same part number.  Bikebandit.com shows different spring part numbers between 75 and 73.  The manual doesn't catch this that I found?

I'm concerned because I just purchased a set of Barnett clutches, discs, and springs that say it is for 69-78k models.  Now I am not so sure...

The supplement to the 1976 CB750 manual only says that the clutch now has a retaining ring instead of the 6-point little star to hold the basket in.  Nothing about spring length.

[scondon]

I thought that,
- K0 through K7, and F1 all used the same clutch return springs, 31.9 -30.5 mm
- F2 used the 39.6 - 36.8mm springs with stiffer rating (242 lbs from 220 lbs)
- Model A has a single large return spring, 39 - 36 mm

In what model did the 35.5 mm springs appear?  Anyone have a fiche with contradictory specs?

   When I was researching how to upgrade the clutch on my F2 I found that the spring length was longer on my model than the ones on the K8, even though they had the same clutch pack. When I dug further I found that the part #'s for the spring were distributed as follows-

K0-K4/   #95014-751-40

K6-K8-F0-F1/   #22401-323-003

F2-F3/    #22401-410-000


    The only model that I am positive about being longer is the F2. Not sure what the different part #'s refer to in the K models. Usually, in the Honda Shop Manual, the difference in specs will show only in the supplement for the year in which they changed (K5?).

  fatcaat, I used the Barnett pack in my F2. I think you just want the new disks/plates to have the same stack height as the stock ones you're replacing. The springs are heavy duty and might not match stock spec's, but I believe you will be fine with them.

[Tower]

As far as OEM part numbers go, I have:
Clutch springs
k0-k2?,
K3-K5 #95014-75140
F1, K6 - K8 #22401-275-000
F2, and all Ks and Fs sold after '79 #22401-425-000

Edit: the sizing on the K3-K5 springs is "14"  ( 1.4" x 25.4 mm/inch = 35.56mm)?

[scondon]

 I like to learn something new, even if it is learning that I don't know much

  I looked in the 69-78 CB750 Shop Manual(with supplements) and could not find any info of any spring change at any time, even on my F2 which I know to be different. So I looked in my '78 750K/F Shop Manual and it shows the '78 K bike as having the same length and service limits what Tower states(31.9 -30.5 mm) which is same as shown in 69-78 Shop Manual for early K bikes. Why the different part #'s? I haven't a clue. I can find no reference, anywhere, to a 35.5 spring.

Edit: the sizing on the K3-K5 springs is "14"  ( 1.4" x 25.4 mm/inch = 35.56mm)?

   Where'd ya cull that info from

[eurban]

Somewhere around 76 Honda changed the clutch assembly, adding a double thickness riveted steel plate in the center of the clutch sandwhich.  The entire depth of the clutch package was increased.  The outer most friction disc also had a wider tang that mated with a wider slot in the outermost portion of the basket.  If your clutch is this later type then your "69-78 kit" will probably not work correctly as it is probably designed for the earlier clutch.  I ran into this problem with APE's extra plate performance clutch when I tried to use it on my 78ks clutch.  Make sure that you examine you clutch parts carefully and compare the stock pieces to the Barnett setup. . . . .From what I have read, Honda used stronger springs (don't know about length) in the F2/F3 clutches to keep things from slipping with the higher powered engine.  Clutch springs aren't particularly expensive and I have had good luck with heavier springs that came with the APE kit (the only part of the kit that I could use).  Perhaps you should just buy a set of heavy duty springs and not worry about the wear limits of the stock ones?

[Tower]

@scondon, in the original Honda Parts Manual for CB750K3 - K5, see block E-9 Clutch.  Look very closely at the description for part Ref No. 12.  Description reads..."SPRING 14, CLUTCH"
In most cases, whenever a sizing is applicable to the part description, its accompanied by some kind of a measurement, hence, I'm guessing that the 14 refers to 1.4".

Edit: Further clarification on clutch spring OEM part numbers...

K0, K1 w/Serial numbers below 1042806: #22401-300-000 (set of 4: #22041-300-000)
K1 w/Serial numbers over 1042805: #22401-268-000
K2 - K5: #95014-75140
F1, K6 - K8: #22401-275-000
F2, and all Ks and Fs sold after '79: #22401-425-000

K2 - K5 clutch springs are referred to in the Honda Parts Manuals as "SPRING 14, CLUTCH"
all others are referred to as "SPRING, CLUTCH"

[fatcaaat]

Well.  I got my Barnett Clutch Kit today.  this kit is interesting.  It comes with the materials to work with either the early model clutches or the later up to 1978k models.

So, my 1976K worked fine...I fit in the 6A fibers and 1B fiber and all new plates.  The HD clutch springs were an exact match to the ones that were in there.  Everything went together really easy. 

No miles yet...but I think I have the adjustment down now.  No more grinding and clunking either...like butter...

Now, if only my battery would finally arrive.

[HondaMan]

@scondon, in the original Honda Parts Manual for CB750K3 - K5, see block E-9 Clutch.  Look very closely at the description for part Ref No. 12.  Description reads..."SPRING 14, CLUTCH"
In most cases, whenever a sizing is applicable to the part description, its accompanied by some kind of a measurement, hence, I'm guessing that the 14 refers to 1.4".

Edit: Further clarification on clutch spring OEM part numbers...

K0, K1 w/Serial numbers below 1042806: #22401-300-000 (set of 4: #22041-300-000)
K1 w/Serial numbers over 1042805: #22401-268-000
K2 - K5: #95014-75140
F1, K6 - K8: #22401-275-000
F2, and all Ks and Fs sold after '79: #22401-425-000

K2 - K5 clutch springs are referred to in the Honda Parts Manuals as "SPRING 14, CLUTCH"
all others are referred to as "SPRING, CLUTCH"

Tower: most of the info I have points to the 22401-300-000 until K3.
There was also a 22401-300-010 for the K2 (still had one in a Honda bag a few years ago).
It looked the same, though. Both of these were found in the clutches with "square" corks on the clutch plates, IIRC.
The --75140  parts showed up in the 1980s, long after the bikes were out of production (and always confused me...). I never figured out what they were about, but they fit OK. 
Those you have as  "F1, K6 - K8: #22401-275-000" that I've seen are used with the slanted-cork clutch plates.

By the way, I have a set of brand-new, in-the-bag, slanted-cork clutch plates for those later F/K7-K8 models. I wouldn't mind selling them to someone here, as I don't want them in my K2. An online Honda shop sold them to me as "K2" plates, wouldn't take them back. 

[Tower]

@HondaMan, the OEM part numbers I show are from the parts lists I believe were prepared by Honda, USA (as their disclaimer is attached to each list) and were produced in five groups:
 1) K, K1, K2 published December 20, 1971
 2) K3, K4, K5 published September 10, 1976
 3) F1, K6 published December? 1976
 4) K7, K8 published December 1977
 5) F2, K models after '79 (unknown publication date). 

It appears that some of the part number changes were to do with changes in the manufacturing process and not to the performance specification, ie. they are essentially the same part.  For example, 22041-300-000 and its derivatives were all 1 1/4" springs with 210 lb tension.  The original series were produced using steel without annealing, whereas the subsequent series were produced using an anneal process.
The 22041-268-000 were again essentially the same, but were part of a new clutch design introduced part way through the production year in 1971.

The 95014-75140 springs are 1 3/8" 220 lb. tension.  These springs were introduced in 1971 for the USA K2 model and applied to models K3 - K5 as those models were rolled out into the various countries around the world.

In 1976 a new clutch was introduced along with the 1 1/2" springs with 240 lb tension.  This spring design was sold in different parts of the world using various part numbers. In the USA it was 22401-425-000.  Not all Ks worldwide after 1978 received the same clutch upgrade.  The upgrade can be identified by the addition of a rivetted centre steel plate that lengthened the clutch housing an additional 1/4".  Those Ks that did not upgrade still used the 22401-275-000 part and its derivatives.  Indeed, this is the OEM spring that is, so far, the most difficult about which to get accurate information.

[mycb750k6]

Couldn't resist resurrecting this topic since I just opened up a clutch with "long" springs in it. If you look at the partsnmore page ( =engine]http://www.partsnmore.com/parts/honda/cb750/?filters[category]=engine ), they list three sets of springs, two long ones and one shorty for the early Ks.