Author Topic: 750F Clutch issue  (Read 2178 times)

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Offline 13enning21

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750F Clutch issue
« on: October 23, 2015, 11:46:20 am »
Hey gents,

This is my first post and my first bike actually.

A 1978 CB750F. I picked it up last week. It's kinda beat up but runs pretty well the only thing that makes it unridable is the clutch.

When you pull the clutch handle its stiff as a rock. Some of the forum topics I read on here said it could be the cable. Mine was gunky and stuff so I bought a new one. That still didn't help.


Does anyone have any ideas? Clutch disc maybe? I have a lot of experience on working with cars so I'm mechanically savy just not bikes. I'm eager to learn

Thanks for reading

Here's the bike. The po made a super cool seat out of a skateboard and foam...

Offline 13enning21

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Re: 750F Clutch issue
« Reply #1 on: October 25, 2015, 06:54:22 pm »
Any help here?

Online scottly

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Re: 750F Clutch issue
« Reply #2 on: October 25, 2015, 07:39:54 pm »
The clutch lever on the right side of the motor and/or the cable may be out of adjustment.
As far as help, my advice is to ditch the "cool" skateboard seat; the stock F looks better, IMHO. ;) 
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Offline HondaMan

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Re: 750F Clutch issue
« Reply #3 on: October 25, 2015, 07:58:09 pm »
There aren't many things that can make these clutches operate that stiffly. One is the cable (if it drags inside, like old and worn), another is a poor job of reassembly by someone else, or incorrect springs.

Do you know the history of the bike?
See SOHC4shop@gmail.com for info about the gadgets I make for these bikes.

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Blood is thicker than water, but motor oil is thicker yet...so, don't mess with my SOHC4, or I might have to hurt you.
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Link to Hondaman Ignition: http://forums.sohc4.net/index.php?topic=67543.0

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Offline Airborne 82nd

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Re: 750F Clutch issue
« Reply #4 on: October 25, 2015, 08:00:31 pm »
Have you gone through the complete adj. As per the Honda service manual?
Keep the seat it goes well with the tail light. With the motor off bike in gear lever pulled in. Will the bike roll?

Offline 13enning21

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Re: 750F Clutch issue
« Reply #5 on: October 25, 2015, 10:59:32 pm »
Yea I definitely need a new seat haha. It's ridiculous.

I do not know any history on the bike. I bought from a guy who owned it for 5 months. Got it running and got it impounded and sold it to pay off his tickets for unlicensed riding.

I followed a clutch adjustment guide on here I'm not sure if that was the Honda one.
The bike will not roll in gear with the lever pulled in.


How should the tension on the clutch lever feel? The part the cable connects to.

Offline madmtnmotors

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Re: 750F Clutch issue
« Reply #6 on: October 26, 2015, 05:36:32 am »
How should the tension on the clutch lever feel?


What is your level of riding experience? If it is slim to none, then I would suggest you find a friend that is familiar with riding motorcycles come over and give you their opinion on the amount of force required at the clutch lever. If you do have a good deal of riding experience, the I would suggest lubing the clutch cable and checking for freedom of movement of the cable itself. You could go ahead and order stock clutch springs, since these are about the only two items that could likely affect clutch pull to the extent you describe. If the clutch were not assembled properly then it likely would not function properly...

but I guess anything's possible.
TAMTF...


Wilbur



Projects:
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"P.O. Debacle": http://forums.sohc4.net/index.php/topic,126692.msg1441661.html#msg1441661
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Clean up that nasty harness: http://forums.sohc4.net/index.php?topic=137351.msg1549191#msg1549191
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Charging system diagnosis: http://forums.sohc4.net/index.php?topic=1012.msg8345#msg8345
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Engine Lifting Made Easy: http://forums.sohc4.net/index.php/topic,58210.msg1684742.html#msg1684742
                                      http://forums.sohc4.net/index.php/topic,100352.msg1675840.html#msg1675840
Static and Dynamic Timing: http://www.hondachopper.com/garage/carb_info/timing/timing1.html
Airbox Gasket Replacement: http://forums.sohc4.net/index.php/topic,114485.msg1290000.html#msg1290000
"Café" : http://forums.sohc4.net/index.php/topic,84697.msg953814.html#msg953814
PD Carb Choke Linkage: http://forums.sohc4.net/index.php/topic,100352.msg1669248.html#msg1669248
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Tank Latch: http://forums.sohc4.net/index.php/topic,165975.msg1919495.html#msg1919495
Shorten your forks: http://vintage-and-classic-honda-s.456789.n3.nabble.com/How-to-shorten-forks-td4042465.html DO NOT CUT THE SPRINGS!
Clutch How To: http://vintage-and-classic-honda-s.456789.n3.nabble.com/How-to-change-and-adjust-a-clutch-SOHC-td4040391.html
Late model K7/K8/F2/F3 front sprocket cover removal: http://forums.sohc4.net/index.php/topic,178428.msg2072279.html#msg2072279
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Offline 70CB750

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Re: 750F Clutch issue
« Reply #7 on: October 26, 2015, 07:35:05 am »
After you adjust the clutch, you should be able to move the clutch lever, the one under the cover, with your hand, not all the way but move it a bit feeling the springs pushing back.

Offline 13enning21

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Re: 750F Clutch issue
« Reply #8 on: October 26, 2015, 07:36:58 am »
I have ridden dirt bikes growing up. I'm 20 years old so I'm not super experienced but I know a clutch should no be this stiff. When you squeeze it didn't even move. My cousin who has owned a few bikes was thinking it's the springs but he's starting to think it's a worn clutch.

Offline 13enning21

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Re: 750F Clutch issue
« Reply #9 on: October 26, 2015, 07:38:17 am »

After you adjust the clutch, you should be able to move the clutch lever, the one under the cover, with your hand, not all the way but move it a bit feeling the springs pushing back.

Thanks. I'll check that. I'm going to lube the cable, readjust the cable and see if that helps at all.

Offline madmtnmotors

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Re: 750F Clutch issue
« Reply #10 on: October 26, 2015, 09:51:38 am »
The bike will not roll in gear with the lever pulled in.


I know a clutch should no be this stiff. When you squeeze it didn't even move. My cousin who has owned a few bikes was thinking it's the springs but he's starting to think it's a worn clutch.


At this point I would suggest going "all in" and confirm that the clutch is properly assembled:

>Get a new gasket for the clutch cover. Might as well get a new seal for the kick shaft too. The seal for the clutch lifter shaft doesn't see a lot of oil and even a worn one should not leak much, but you can replace this seal too, just for the sake of being thorough.
>Disassemble the clutch and inspect all components for wear.
>Replace any components that are worn beyond service limits.
>Properly reassemble the clutch.
>Adjust clutch lifter and cable.
>Ride the crap out of it.

EZPZ

I can change out a clutch in about 45 minutes taking my time. Faster if I had to. New friction disks+gasket+seals can be had for about $50. I just bought three clutches for a little more than $100 from CB750 Supply:

3 x Clutch Friction Plate SOHC #2 (CB-70129)  = $15.00
 18 x Clutch Friction Plate SOHC #1 (CB-70128)  = $90.00
 ------------------------------------------------------
 Sub-Total: $105.00


At $5 per disk times seven disks equals $35 for new friction disks.


The later models (77/78) will use ONE CB-70129 and SIX CB-70128 for a total of seven disks. The early models will use seven of the CB-70128 so disregard the product description that seems to imply ALL models use seven of the CB-70128, because the later models only use six plus one CB-70129. I may be doing some drag racing soon, so I am stocking up on "consumables".

If you do replace the friction disks, be sure to soak them overnight in motor oil to help prevent initial "sticktion".
« Last Edit: October 26, 2015, 12:24:46 pm by madmtnmotors »
TAMTF...


Wilbur



Projects:
"Evolution": http://forums.sohc4.net/index.php?topic=100352.0
"P.O. Debacle": http://forums.sohc4.net/index.php/topic,126692.msg1441661.html#msg1441661
F2/F3 O-rings: http://forums.sohc4.net/index.php?topic=113672.msg1300721#msg1300721
Cam Tower Studs: https://www.mcmaster.com/#93210a017/=t19sgp
Clean up that nasty harness: http://forums.sohc4.net/index.php?topic=137351.msg1549191#msg1549191
http://forums.sohc4.net/index.php/topic,148188.msg1688494.html#msg1688494
http://forums.sohc4.net/index.php/topic,139544.msg1579364.html#msg1579364
                                          
Charging system diagnosis: http://forums.sohc4.net/index.php?topic=1012.msg8345#msg8345
Get the manuals: http://manuals.sohc4.net/cb750k/
The Dragon: http://forums.sohc4.net/index.php?topic=45183.msg1571675#msg1571675
Headlight Switch: http://forums.sohc4.net/index.php?topic=113986.msg1283236#msg1283236
Branden's leak free top end thread: http://forums.sohc4.net/index.php?topic=107040.0
Engine Lifting Made Easy: http://forums.sohc4.net/index.php/topic,58210.msg1684742.html#msg1684742
                                      http://forums.sohc4.net/index.php/topic,100352.msg1675840.html#msg1675840
Static and Dynamic Timing: http://www.hondachopper.com/garage/carb_info/timing/timing1.html
Airbox Gasket Replacement: http://forums.sohc4.net/index.php/topic,114485.msg1290000.html#msg1290000
"Café" : http://forums.sohc4.net/index.php/topic,84697.msg953814.html#msg953814
PD Carb Choke Linkage: http://forums.sohc4.net/index.php/topic,100352.msg1669248.html#msg1669248
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Follow up on your damn posts: http://forums.sohc4.net/index.php/topic,144305.msg1791605.html#msg1791605
Taiwanese Cam Chain Tensioners:  http://forums.sohc4.net/index.php/topic,155043.msg1774841.html#msg1774841
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Tank Latch: http://forums.sohc4.net/index.php/topic,165975.msg1919495.html#msg1919495
Shorten your forks: http://vintage-and-classic-honda-s.456789.n3.nabble.com/How-to-shorten-forks-td4042465.html DO NOT CUT THE SPRINGS!
Clutch How To: http://vintage-and-classic-honda-s.456789.n3.nabble.com/How-to-change-and-adjust-a-clutch-SOHC-td4040391.html
Late model K7/K8/F2/F3 front sprocket cover removal: http://forums.sohc4.net/index.php/topic,178428.msg2072279.html#msg2072279
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Offline rotortiller

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Re: 750F Clutch issue
« Reply #11 on: October 26, 2015, 10:32:06 am »
Sitting bikes will sometimes have a sticking clutch and they won't roll with the clutch pulled in while in gear. Suggest you ride the thing in first and pull the clutch in while extracting some power on and off  from the engine. Otherwise take it apart.

Offline 13enning21

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Re: 750F Clutch issue
« Reply #12 on: December 06, 2015, 01:24:00 pm »


Bump from the dead. I'm currently pulling it apart though. This a look at the clutch disk(s). It looks like someone has been in here recently and there were a lot of loose bolts that should probably should have been tight. Is this disk past its wear limits?

Offline 01Thomas

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Re: 750F Clutch issue
« Reply #13 on: December 06, 2015, 01:46:17 pm »
Or seeing as you don't have a working clutch at the moment, try this procedure with the bike on the mainstand (possibly raised by having a plank under the mainstand) and your weight well forward, with a solid wall about a foot or two in front of the front wheel. That way if something goes wrong (back wheel touches the ground) the speed will be low and bike will stall pretty harmlessly.



Sitting bikes will sometimes have a sticking clutch and they won't roll with the clutch pulled in while in gear. Suggest you ride the thing in first and pull the clutch in while extracting some power on and off  from the engine. Otherwise take it apart.
1971 Honda CB750 Four K1 [Engine: CB750E-1113521 / Frame: CB750-1113838]
1977 Seeley Honda CB750F (F1) [Engine: CB750E-2551214 / Frame No: SH7-655F]

'96 Yamaha YZF750SP & '81 Moto Guzzi SP1000 & '80 Moto Guzzi 850 LeMans II & '82 Bimota KB-3 [Frame No 49] & '66 Ducati 50 SL/1 & '53 Miele K-50 & '38 Miele 98

Offline madmtnmotors

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Re: 750F Clutch issue
« Reply #14 on: December 06, 2015, 03:02:12 pm »
Is this disk past its wear limits?

Wear limits are given as a minimum disk thickness in the manual. How thick are your disks?
TAMTF...


Wilbur



Projects:
"Evolution": http://forums.sohc4.net/index.php?topic=100352.0
"P.O. Debacle": http://forums.sohc4.net/index.php/topic,126692.msg1441661.html#msg1441661
F2/F3 O-rings: http://forums.sohc4.net/index.php?topic=113672.msg1300721#msg1300721
Cam Tower Studs: https://www.mcmaster.com/#93210a017/=t19sgp
Clean up that nasty harness: http://forums.sohc4.net/index.php?topic=137351.msg1549191#msg1549191
http://forums.sohc4.net/index.php/topic,148188.msg1688494.html#msg1688494
http://forums.sohc4.net/index.php/topic,139544.msg1579364.html#msg1579364
                                          
Charging system diagnosis: http://forums.sohc4.net/index.php?topic=1012.msg8345#msg8345
Get the manuals: http://manuals.sohc4.net/cb750k/
The Dragon: http://forums.sohc4.net/index.php?topic=45183.msg1571675#msg1571675
Headlight Switch: http://forums.sohc4.net/index.php?topic=113986.msg1283236#msg1283236
Branden's leak free top end thread: http://forums.sohc4.net/index.php?topic=107040.0
Engine Lifting Made Easy: http://forums.sohc4.net/index.php/topic,58210.msg1684742.html#msg1684742
                                      http://forums.sohc4.net/index.php/topic,100352.msg1675840.html#msg1675840
Static and Dynamic Timing: http://www.hondachopper.com/garage/carb_info/timing/timing1.html
Airbox Gasket Replacement: http://forums.sohc4.net/index.php/topic,114485.msg1290000.html#msg1290000
"Café" : http://forums.sohc4.net/index.php/topic,84697.msg953814.html#msg953814
PD Carb Choke Linkage: http://forums.sohc4.net/index.php/topic,100352.msg1669248.html#msg1669248
                                    http://forums.sohc4.net/index.php/topic,110931.msg1248354.html#msg1248354
                                    http://forums.sohc4.net/index.php/topic,48858.msg515204.html#msg515204
Follow up on your damn posts: http://forums.sohc4.net/index.php/topic,144305.msg1791605.html#msg1791605
Taiwanese Cam Chain Tensioners:  http://forums.sohc4.net/index.php/topic,155043.msg1774841.html#msg1774841
Gumtwo Seat Cover: http://forums.sohc4.net/index.php/topic,164440.msg1897366.html#msg1897366
Primary Drive: http://forums.sohc4.net/index.php/topic,166063.msg1919278.html#msg1919278
Tank Latch: http://forums.sohc4.net/index.php/topic,165975.msg1919495.html#msg1919495
Shorten your forks: http://vintage-and-classic-honda-s.456789.n3.nabble.com/How-to-shorten-forks-td4042465.html DO NOT CUT THE SPRINGS!
Clutch How To: http://vintage-and-classic-honda-s.456789.n3.nabble.com/How-to-change-and-adjust-a-clutch-SOHC-td4040391.html
Late model K7/K8/F2/F3 front sprocket cover removal: http://forums.sohc4.net/index.php/topic,178428.msg2072279.html#msg2072279
630 to 530 conversion: http://forums.sohc4.net/index.php/topic,180710.msg2094423.html#msg2094423

Sent from my Tandy TRS-80!

Offline 13enning21

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Re: 750F Clutch issue
« Reply #15 on: December 10, 2015, 01:45:23 pm »
New disk and springs should be here Monday. I measured my springs and they we're blow the limit. When i pull the clutch there was just no spring tension. New springs should fix it

Offline HondaMan

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Re: 750F Clutch issue
« Reply #16 on: January 10, 2016, 01:22:14 pm »
New disk and springs should be here Monday. I measured my springs and they we're blow the limit. When i pull the clutch there was just no spring tension. New springs should fix it

Well....here's a few tips, to help you wade through the myths and incorrect parts we are getting today, and how they will affect your "F" clutch:

1. Get some calipers or a 1" micrometer to measure the plate thickness, you will need it. Harbor Freight sells a passable set of calipers for $10 that will work well enough for this project.
2. The plates shown in the pic above are NOT Honda plates. They are someone's aftermarket plates. This is where the problems begin. The (proper) springs in your clutch are slightly longer than the early CB750 springs, and measuring them is important, but ONLY if you are sure of both the ones you SHOULD have, and the ones you NOW have. For example, if someone put springs in from a K0-K6 bike, they are shorter than the ones you need. In that case, measure the new ones you are getting, to make sure they are the right length for the "F" bike like yours, or the first problem (soft lever) will reappear. And, if you are measuring 'early' springs, their full length is shorter than the worn-out length of "F" springs.
3. The OEM clutch plates for the bike are supposed to be 0.141" thick when new. Chances are, you are about to receive plates just like the ones you just removed, which will be about 0.135" thick. Since the worn-out spec in these bikes is 0.131" thickness, you're starting out with seriously worn plates: we have seen this happen a LOT since 2010 when these plates started getting mixed into our 'generic parts supply' houses. The thinner ones belong to modern superbikes, and the only dimensions they share with our engines are the OD and tab sizes: the plates are thinner because the superbikes have more clutch plates. The moral here is: measure your new plates before attempting to use them. Also: the top plate on the "F" clutch is different from the other plates in the stack: it has slant-cut cork blocks on it, and wider tabs around the outside edge. There is also 1 'double plate' in the stack, sometimes found just under this top plate, sometimes found as #4 plate in the stack. This 'double plate' consists of 2 steel plates riveted together with leaf springs between, to make a cushion plate. If the clutch was "modded' per Honda's service bulletin about "rattling clutch issue", then this plate has been replaced with a very thick solid steel plate instead, from a GL1000 clutch.
4. Measure your metal plates. If someone installed "modern" metal plates, they are ALSO thinner than the OEM plates. The combination of thinner steel and thinner cork plates leaves you with an unusable clutch, as it will not engage, regardless of spring pressure.

There are some things that can be done, if you don't opt to buy Honda's OEM parts (I get the correct ones from South Sound Honda, myself...). This involves modifying some things in the plate stack, adding plates, changing plates, etc., but first and foremost, you have to start by measuring the thickness of the new plates you're getting AND the metal plates you have. So, report back when the new plates arrive and you measured them? Then we can possibly help out intelligently. ;)
See SOHC4shop@gmail.com for info about the gadgets I make for these bikes.

The demons are repulsed when a man does good. Use that.
Blood is thicker than water, but motor oil is thicker yet...so, don't mess with my SOHC4, or I might have to hurt you.
Hondaman's creed: "Bikers are family. Treat them accordingly."

Link to Hondaman Ignition: http://forums.sohc4.net/index.php?topic=67543.0

Link to My CB750 Book: https://www.lulu.com/search?adult_audience_rating=00&page=1&pageSize=10&q=my+cb750+book

Link to website: www.SOHC4shop.com