Author Topic: 1975 CB750F strange clutch issue after a pull apart to check slipping issues.  (Read 1925 times)

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Offline kaptainkid1

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This is the most common way lifters are broken. To correct it remove and turn the four posts one hole either way. Next time, mark the parts before removing.
Thank you for helping out. You are correct on my solution for my non shifting Honda.

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1975 Honda CB750F Daily Rider      
1974 BMW R90S Barn Find
1995 BMW R1100GS Dual Sport Daily
1996 Triumph 900 Adventurer Bobber

Offline kaptainkid1

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Here are some clutch pressure plates aligned correctly before putting into the clutch outer basket. Don r tried to explain the misalignment in his photos and my brain couldn't understand it. So for other CB owners having this problem. Here are some photos which your clutch plates pack should look like from the side view before packing them in Clutch outer basket.
Thanks for everyone's help now going to fix the next problem second gear slippage on hard throttle. Only happens in second and maybe 3rd if practically never.

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1975 Honda CB750F Daily Rider      
1974 BMW R90S Barn Find
1995 BMW R1100GS Dual Sport Daily
1996 Triumph 900 Adventurer Bobber

Offline HondaMan

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Your clutch pack is missing a plate.
In the 1975 clutch, there is a double-steel plate that has little springs in between them, and rivets holding it together. The rivets get loose and make the engine 'rattle' at low speeds, so they often get removed. However, this leaves the total stack height short by 1 steel plate. So, add another steel plate, right on top of another steel plate, to restore the height. Then the spring pressure will return and the slip will likely stop altogether.
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

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Offline kaptainkid1

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Your clutch pack is missing a plate.
In the 1975 clutch, there is a double-steel plate that has little springs in between them, and rivets holding it together. The rivets get loose and make the engine 'rattle' at low speeds, so they often get removed. However, this leaves the total stack height short by 1 steel plate. So, add another steel plate, right on top of another steel plate, to restore the height. Then the spring pressure will return and the slip will likely stop altogether.
So I can stack another metal plate or not?
The reason why I say this is because i have been running set up for 10k and only recently this issue is popping up.

My issue isnt a complete slip in 2nd gear. My issue isnt a 2nd gear total slippage. It very quick and last about 1 second and happens very randomly. In other words it feels like 1 second slip and it can happen back to back in 4 second pull. It also can run in 2nd gear and not slip. It feels like it popping out of gear and harash slip back into gear.
Also with a slipping clutch wouldn't slipping in 3rd when it pulls hard? 
Its a very weird sensation and I have had slipping clutches before and this doesnt feel like that.
Another possible problem?
I will put another metal plate but if that doesnt fix the problem what else can it be?

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« Last Edit: July 02, 2022, 11:15:18 PM by kaptainkid1 »
1975 Honda CB750F Daily Rider      
1974 BMW R90S Barn Find
1995 BMW R1100GS Dual Sport Daily
1996 Triumph 900 Adventurer Bobber

Offline Jerry Rxman Griffin aka MuthaF'er

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No, there is NOT a double steel in the 75 CB750F stock clutch. I have to disagree on this as an original owner of a 75 CB750F. Plus my 1975 American Honda parts manual disagrees also.   

The 75 clutch has 6 steel plates (22321-283-000 Plate B, clutch), 6 fiber plates (22201-300-000 Disk, clutch friction) and 1 fiber plate (disk, B clutch friction). As I have stated before the double steel did not appear until the 77/78 clutch upgrade. 

PM your phone number and I will text the pages of the parts manual with the parts list and the diagram if you would like
« Last Edit: July 02, 2022, 11:49:36 PM by Jerry Rxman Griffin aka MuthaF'er »
As of today 3/13/2012 my original owner 75 CB750F has made it through 3 wives, er EX-wives. Free at last.  ;-)

Offline ekpent

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The second gear issue is hopefully not  worn gear dawgs when the two gears engage in the transmission. Second gear is the most popular for failure. When really bad it will pop out of second into a false neutral. Usually bad clutches like to slip and are more noticeable in the higher gears.

Offline PeWe

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I bought a used primary chain hub written to be from a 750F 1975 a few years ago
It was the earlier style without circlip groove before K6 1976.

My K6 1976 has same clutch fibers as the later engines 77/78,  outer fiber has wider tabs which need the K6 steel basket.
But still not double metal plate that need the later clutch hub a few mm deeper AND the deeper outer steel basket, F2-3, K7-8.

I bought an extra K6 clutch from USA ebay. Same model.

That bike has got the later style 77/78 with double metal disc. The later steel basket + the later deeper alu hub. (Had been in an F2-78.
Reused the clutch fibers.
« Last Edit: July 03, 2022, 12:28:14 PM by PeWe »
CB750 K6-76  970cc (Earlier 1005cc JMR Billet block on the shelf waiting for a comeback)
CB750 K2-75 Parts assembled to a stock K2

Updates of the CB750 K6 -1976
http://forums.sohc4.net/index.php/topic,180468.msg2092136.html#msg2092136
The billet block build thread
http://forums.sohc4.net/index.php/topic,49438.msg1863571.html#msg1863571
CB750 K2 -1975  build thread
http://forums.sohc4.net/index.php/topic,168243.msg1948381.html#msg1948381
K2 engine build thread. For a complete CB750 -75
http://forums.sohc4.net/index.php/topic,180088.msg2088008.html#msg2088008
Carb jetting, a long story Mikuni TMR32
http://forums.sohc4.net/index.php/topic,179479.msg2104967.html#msg2104967

Offline kaptainkid1

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The second gear issue is hopefully not  worn gear dawgs when the two gears engage in the transmission. Second gear is the most popular for failure. When really bad it will pop out of second into a false neutral. Usually bad clutches like to slip and are more noticeable in the higher gears.
Do you think it can be shifting springs going bad.
At 10:50 minute mark is the issues I'm going to check next.
Anyone else have an opinion to my werid 2nd gear popping out for a quick second and back into gear problem?

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1975 Honda CB750F Daily Rider      
1974 BMW R90S Barn Find
1995 BMW R1100GS Dual Sport Daily
1996 Triumph 900 Adventurer Bobber

Offline HondaMan

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Your clutch pack is missing a plate.
In the 1975 clutch, there is a double-steel plate that has little springs in between them, and rivets holding it together. The rivets get loose and make the engine 'rattle' at low speeds, so they often get removed. However, this leaves the total stack height short by 1 steel plate. So, add another steel plate, right on top of another steel plate, to restore the height. Then the spring pressure will return and the slip will likely stop altogether.
So I can stack another metal plate or not?
The reason why I say this is because i have been running set up for 10k and only recently this issue is popping up.

My issue isnt a complete slip in 2nd gear. My issue isnt a 2nd gear total slippage. It very quick and last about 1 second and happens very randomly. In other words it feels like 1 second slip and it can happen back to back in 4 second pull. It also can run in 2nd gear and not slip. It feels like it popping out of gear and harash slip back into gear.
Also with a slipping clutch wouldn't slipping in 3rd when it pulls hard? 
Its a very weird sensation and I have had slipping clutches before and this doesnt feel like that.
Another possible problem?
I will put another metal plate but if that doesnt fix the problem what else can it be?

Sent from my SM-A526U using Tapatalk

The second gear issue is hopefully not  worn gear dawgs when the two gears engage in the transmission. Second gear is the most popular for failure. When really bad it will pop out of second into a false neutral. Usually bad clutches like to slip and are more noticeable in the higher gears.
Do you think it can be shifting springs going bad.
At 10:50 minute mark is the issues I'm going to check next.
Anyone else have an opinion to my werid 2nd gear popping out for a quick second and back into gear problem?


Yep. Bent "L" shift fork inside, and now with worn gear dogs on the C5 gear, with ovalled-out slots in the C2 gear.

This was a chronic issue in the K0/1/2 bikes, and the shift drum (and later, the fork pins) was changed to help provide a more positive shift into 2nd, with an easier-to-find Neutral.

What happens is this, chronologically:
1. The bike is either frequently half-shifted into 2nd (because of a too-soft lift on the shifter from the rider's toe), or the bike fell over to the left side when not running, and came to rest on the shifter with the gearbox not shifted into 2nd, but resting dog-against-gear (C2-C5 pair) instead. This bends the shifter fork.
2. With continued usage and teh C2-C5 gears not being fully meshed, the slots in the C5 wear in a taper and the edges of the dogs on the C2 gear wear likewise in the opposite direction.
3. The pressures of the engine accelerating cause the middle section rib of the engine to twist slightly (under heavy loaads or throttle) and the barely-engaged C2-C5 dogs-slots pop out for one or two revolutions. This is really jerky, and sometimes noisy as well.

The solution usually entails a new shifter drum, which by now is probably also damaged in the Neutral bump site, and a new "L" shift fork (or a straight used one) and the C2-C5 gears either replaced with good ones, or pull them out and send them to be refitted. This 'fixup' costs about $150 (last ones I did), so sometimes finding another gearbox or the C2-C5 gears is cheaper. The shift fork is harder to find. The drums are pretty available.

If you pull yours apart, put up the pictures of these parts. If I have some to match, I might be able to help. When you are splitting the cases, the first gear out of the countershaft bearing housing is the C2, the next one is the C5 gears. The "L" shift fork is the one closest to the Left side of the engine.

This all said: I once rebuilt a 750K1 engine with over 55k miles on it. These 2 gears were VERY worn, and one of the dogs was missing on the C2 gear. When I asked the owner about it, he said he had
"...tapped the bike with my car's fender when pulling into the garage one night and it fell over, and I left it there all night. The next day I picked it up off of (I think he said it was a concrete block it hit on...) that the shifter was resting on, and it had this problem. When I ran it, the tranny locked up and killed the engine when I tried to pull away from a stop. I pulled the pan and found the broken-off dog, took it out, and rode on by skipping 2nd gear and going from 1st to 3rd."
- for more than 40k miles he rode like this! I replaced the above 4 parts in that one and it still runs today.
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

Offline bryanj

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Having read this post for the first time the big problem is using the wrong words, it was not "slipping" in 2nd gear it was "jumping" out of gear and back in.
Semi Geriatric ex-Honda mechanic and MOT tester (UK version of annual inspection). Garage full of "projects" mostly 500/4 from pre 73 (no road tax in UK).

Remember "Its always in the last place you look" COURSE IT IS YOU STOP LOOKIN THEN!