Author Topic: Clutch Hub modification posts  (Read 13315 times)

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Offline 70CB750

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Re: Clutch Hub modification posts
« Reply #25 on: August 05, 2015, 03:12:51 AM »
Yes, it should.

Also consider heavier oil 20w50 with some zink additive.
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Offline PeWe

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Re: Clutch Hub modification posts
« Reply #26 on: August 05, 2015, 04:52:52 AM »
Search for:
difficult to find neutral when warm
dragging clutch when cold
These can also be Oil related. Motorcycle oil for wet clutch 20W-50 with zinc additive as mentioned earlier if oil has not much of it from the beginning. Some have a lot.

Additional holes in clutch hub for smoother starts + ensure oil pressure: http://forums.sohc4.net/index.php?topic=78643.0
I did the additional holes only, no grinding.

Dragging clutch if you use Cycle X clutch plates. (Some with Barnett HD clutch has reported that too in the forum) I had CycleX plates and the clutch was sticked together after a night. Replaced them with cheap std clutch plates from cruzinimage_co. Smooth starts and NO slippage yet despite +80 WHP. EDIT: I use harder clutch springs with washer under.
http://www.ebay.com/itm/76-78-HONDA-CB750K6-CB750K7-CB750F2-CLUTCH-FRICTION-PLATE-1145-/161408453864?vxp=mtr&hash=item2594b18ce8

Problem to find neutral when warm solved with other oil.  You will find if you search, no meaning to ask here when information is discussed many times. :) :)
« Last Edit: August 05, 2015, 11:17:05 AM 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

Online scottly

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Re: Clutch Hub modification posts
« Reply #27 on: August 08, 2015, 07:32:32 PM »
I compared a K7 hub to a K1 hub; both had the same 12 hole pattern, and neither had the holes beveled. The holes closest to the bottom of the web were drilled deeper on the K7, which formed a sort of trough. I drilled those holes deeper on the K1 hub, and added 2 holes between the original holes. I did the bevel with a round burr in a Dremel.
Don't fix it if it ain't broke!
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Offline DWS

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Re: Clutch Hub modification posts
« Reply #28 on: August 09, 2015, 08:41:18 AM »
Thank you guys for the info.
I used 20w 50w already but i think i'll try Lucas bran?
« Last Edit: August 09, 2015, 08:46:31 AM by DWS »
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Offline HondaMan

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Re: Clutch Hub modification posts
« Reply #29 on: August 09, 2015, 12:57:28 PM »
I compared a K7 hub to a K1 hub; both had the same 12 hole pattern, and neither had the holes beveled. The holes closest to the bottom of the web were drilled deeper on the K7, which formed a sort of trough. I drilled those holes deeper on the K1 hub, and added 2 holes between the original holes. I did the bevel with a round burr in a Dremel.


You're certainly on the right track!
Over the years, the fixes have been to either add an extra hole in each 1/4 section of the hub, or else bevel or modify the existing ones. Today I mostly add some tiny vee-shaped grooves toward the upstream rotation direction to widen the capture zone of the oil film that is slipping around the inside of the hub. This has worked better than the 'extra-hole' approach on the 750, and it doesn't weaken the hub (important for the racers) at all. These grooves are barely .006" deep, cut with either a Dremel saw bit or grinder (flat) bit. I also rout away the tiny "dam" that always exists in the most-inner hole in the web of the casting (all the way at the back of the hub): this then creates a natural high-capture point of the oil. In the end, when I first did this last mod it REALLY improved the hot-release of the plates in the clutch, indicating that this is probably the very site where most of these clutches hang up when hot.
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 chewbacca5000

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Re: Clutch Hub modification posts
« Reply #30 on: August 09, 2015, 04:42:17 PM »
Hondaman,

Here is one thing I don't understand why does the steel plates have a smooth beveled side and a sharp side?  I have taken may hubs apart and notice they are all marred on the spleens when the steels dig in?

Would it make sens to debur the steel plates so they don't have that sharp edge?

Offline MCRider

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Re: Clutch Hub modification posts
« Reply #31 on: August 09, 2015, 05:16:53 PM »
sub
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Re: Clutch Hub modification posts
« Reply #32 on: August 09, 2015, 07:36:09 PM »
While cleaning the pressure plate, I noticed areas at the bases on two of the posts where the springs had left significant wear marks. It occurred to me that the springs hadn't been properly seated in the pockets in the hub. I'd never thought about it before; I'd always assumed the springs would naturally fall into place. When I assembled my clutch today, I initially only tightened the lifter plate screws enough to lightly hold the springs in place. I could then get a finger in on either side of each spring and wiggle them around to make sure they were seated.
Don't fix it if it ain't broke!
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Offline HondaMan

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Re: Clutch Hub modification posts
« Reply #33 on: August 14, 2015, 05:18:47 PM »
While cleaning the pressure plate, I noticed areas at the bases on two of the posts where the springs had left significant wear marks. It occurred to me that the springs hadn't been properly seated in the pockets in the hub. I'd never thought about it before; I'd always assumed the springs would naturally fall into place. When I assembled my clutch today, I initially only tightened the lifter plate screws enough to lightly hold the springs in place. I could then get a finger in on either side of each spring and wiggle them around to make sure they were seated.

You're right on track, there, Scottly, but also watch out for the occasional distorted foot on the springs. Once in a great while I have seen their ends warp away from their once-flat-ground surface, probably on springs that had marginal heat-treat when they were made. I replace them when this happens. Honda has a test for them that includes making sure they have all the same spring tension: I didn't include this in my book because no one has a spring gage(!) today. For a bench-test, I use a flat pair of aluminum plates and a brick: I measure the compression of the spring in between 2 plates with a brick's weight and if they vary more than a few thousandths of an inch, I replace the [weak] one(s). Their open length must also be within 0.1mm of each other. easy to check side-by-side.
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 HondaMan

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Re: Clutch Hub modification posts
« Reply #34 on: August 14, 2015, 05:21:14 PM »
Hondaman,

Here is one thing I don't understand why does the steel plates have a smooth beveled side and a sharp side?  I have taken may hubs apart and notice they are all marred on the spleens when the steels dig in?

Would it make sens to debur the steel plates so they don't have that sharp edge?

The splines dig into the hub with use, which is why I like to try to keep them "in pack stack" when I pull one apart, if I am not changing plates. Since they are just stamped plates, it is hard for Honda (or anyone) to make them burr-free. If you are the patient (and OCD) type like me, I like to smooth off the sharper edges, especially with new plate sets.
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

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Re: Clutch Hub modification posts
« Reply #35 on: August 14, 2015, 06:35:46 PM »
Mark, the wear on the posts may have indeed been caused by distorted springs. The K1 spring on the right in the pic of my "spring tester" does appear to lean to the right. Something else I noticed was that the K1 fiction discs were worn unevenly: at the thickest point, they all measured about .140" thick, but 180 degrees from the thickest point some were only .130" thick. I don't know if that's normal or not?
 
Don't fix it if it ain't broke!
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Offline chewbacca5000

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Re: Clutch Hub modification posts
« Reply #36 on: August 14, 2015, 07:08:33 PM »
Guess I am OCD too as I de burred the steel plates in my low mileage k5.  Had to take the clutch pack apart to unstuck the steel plates.  With extra holes drilled and filing off the sharp edges I notices much better movement.

Offline HondaMan

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Re: Clutch Hub modification posts
« Reply #37 on: August 15, 2015, 10:08:54 PM »
Mark, the wear on the posts may have indeed been caused by distorted springs. The K1 spring on the right in the pic of my "spring tester" does appear to lean to the right. Something else I noticed was that the K1 fiction discs were worn unevenly: at the thickest point, they all measured about .140" thick, but 180 degrees from the thickest point some were only .130" thick. I don't know if that's normal or not?
 

That usually only happens if the [top] pressure plate is a little bit warped, or the springs are uneven on one side (like, 2 of them). Interestingly, the clutches still work for a long time like this, unless someone takes them apart and they lose their "friend" next door (then they slip upon reassembly). The clutches that are the most 'forgiving' about this wear are those that have the little spring clip around the upper plate, or the sheet metal retainer (that often got thrown away), or the early K0 style with the steel plate that goes into the bottom of the stack, with just 6 friction plates total, and a steel top plate. These early clutch hubs have steel collars, too, over their mainshaft splines (up through the early K2), for extra strength.
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

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Re: Clutch Hub modification posts
« Reply #38 on: August 15, 2015, 10:20:57 PM »
I checked the springs against a square today, and three of the four were out of square by about 2-3mm.
Don't fix it if it ain't broke!
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Offline PeWe

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Re: Clutch Hub modification posts
« Reply #39 on: August 16, 2015, 01:10:50 AM »
I have washers under my springs (CB750 K6). The washers seated in the pockets, springs can then wiggle around and cause wear on the 4 posts when springs are not held by the pockets. There are deep marks.
I have to do something about it coming winter.
I have an extra complete F2 clutch with double metal plate. Clutch cover too.
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 HondaMan

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Re: Clutch Hub modification posts
« Reply #40 on: August 16, 2015, 10:42:12 AM »
I checked the springs against a square today, and three of the four were out of square by about 2-3mm.

What genre is that bike, Scottly? K2, K6...??
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

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Re: Clutch Hub modification posts
« Reply #41 on: August 16, 2015, 05:10:52 PM »
The motor is a K1 Mark. I was initially going to swap the entire K7 clutch from the same parts bike that had the transmission snap rings installed backwards at the factory (the one that fell over on top of me when it went into gear by itself while on the kick-stand  :o) as it only had 5300 miles, but I couldn't get the K1 clutch basket off the shaft. I ended up using 6 of the K7 friction disks and plates, and 1 each of the best K1 disks and plates, as well as the K7 springs with .075" shims. I put the shims on the outside ends of the springs, but extreme caution was required to make sure they were aligned over the posts when tightening the lifter plate. So far I've only ridden a couple of miles so I can't say if the extra holes have had any effect.
Don't fix it if it ain't broke!
Helmets save brains. Always wear one and ride like everyone is trying to kill you....

Offline HondaMan

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Re: Clutch Hub modification posts
« Reply #42 on: August 16, 2015, 10:39:37 PM »
The motor is a K1 Mark. I was initially going to swap the entire K7 clutch from the same parts bike that had the transmission snap rings installed backwards at the factory (the one that fell over on top of me when it went into gear by itself while on the kick-stand  :o) as it only had 5300 miles, but I couldn't get the K1 clutch basket off the shaft. I ended up using 6 of the K7 friction disks and plates, and 1 each of the best K1 disks and plates, as well as the K7 springs with .075" shims. I put the shims on the outside ends of the springs, but extreme caution was required to make sure they were aligned over the posts when tightening the lifter plate. So far I've only ridden a couple of miles so I can't say if the extra holes have had any effect.

Ow! That's one 'mean' K7!
:(
I had a K5 on top of me in January, took until May before my shoulder worked right again...

Now, the plot thickens: yes, I have seen the post-1976 clutch springs crooked, too. It was mighty rare in the earlier bikes before 1975, though. Around 1972-3 (depending on where the bike was made) they started getting slightly longer springs, although the parts fiche numbers don't always show it. The "new" springs were about 1mm longer, and corresponded to the 7-plate clutch that 'lost' the steel 1st plate on the bottom of the stack.

The steel-banded splines on the K0-K2 early Old Factory bikes are responsible for their death-grip on the mainshaft, even with the C-clip removed. Some of them, up through the K1, also had steel-centered hubs. These tend to rust onto the mainshaft, but were (are?) coveted by racers because the splines never split, even in dragsters. My K2 is one of those, has an early K1 engine (came that way!) that appears to have been made in early 1971, then was probably recycled thru 'refurb' operations for some defect, then ended up in my bike. The clutch hub is absolutely frozen to the mainshaft.
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

Online scottly

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Re: Clutch Hub modification posts
« Reply #43 on: August 16, 2015, 11:13:45 PM »
The K7 basket was retained with a snap ring and with the snap removed it slid right off, but the K1 basket had nothing holding it in place; it was just plain stuck.
Don't fix it if it ain't broke!
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Offline HondaMan

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Re: Clutch Hub modification posts
« Reply #44 on: August 19, 2015, 10:29:21 PM »
The K7 basket was retained with a snap ring and with the snap removed it slid right off, but the K1 basket had nothing holding it in place; it was just plain stuck.

Yep.Tthe early version has the cup washer and the lock-down nut holding it down, and it never moved unless the bike was ridden pretty hard. On those, the clutch can come off more easily! Otherwise, a moderately-ridden pre-K3 mainshaft and clutch basket get to be intimate friends.
;)
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 RandyBMC

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Re: Clutch Hub modification posts
« Reply #45 on: June 21, 2016, 07:41:34 PM »
I compared a K7 hub to a K1 hub; both had the same 12 hole pattern, and neither had the holes beveled. The holes closest to the bottom of the web were drilled deeper on the K7, which formed a sort of trough. I drilled those holes deeper on the K1 hub, and added 2 holes between the original holes. I did the bevel with a round burr in a Dremel.


You're certainly on the right track!
Over the years, the fixes have been to either add an extra hole in each 1/4 section of the hub, or else bevel or modify the existing ones. Today I mostly add some tiny vee-shaped grooves toward the upstream rotation direction to widen the capture zone of the oil film that is slipping around the inside of the hub. This has worked better than the 'extra-hole' approach on the 750, and it doesn't weaken the hub (important for the racers) at all. These grooves are barely .006" deep, cut with either a Dremel saw bit or grinder (flat) bit. I also rout away the tiny "dam" that always exists in the most-inner hole in the web of the casting (all the way at the back of the hub): this then creates a natural high-capture point of the oil. In the end, when I first did this last mod it REALLY improved the hot-release of the plates in the clutch, indicating that this is probably the very site where most of these clutches hang up when hot.

Hi Mark,

Do you happen to have a photo of this?  I have a K8 and haven't pulled the clutch apart yet, but I'm assuming the last of the SOHC production would have the "latest" holes Honda thought would work.  I am waiting for an o-ring at the moment, but I changed the oil pump o-rings and I'm swapping the 5 x 2.5mm on the shifter side for a new one, so the clutch is last bit to boost oil pressure.  In 95F heat in traffic I'm getting a low oil pressure light at idle, so I'm trying to fix that.

Thanks,
Randy

Offline 70CB750

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Re: Clutch Hub modification posts
« Reply #46 on: June 22, 2016, 03:40:57 AM »
I compared a K7 hub to a K1 hub; both had the same 12 hole pattern, and neither had the holes beveled. The holes closest to the bottom of the web were drilled deeper on the K7, which formed a sort of trough. I drilled those holes deeper on the K1 hub, and added 2 holes between the original holes. I did the bevel with a round burr in a Dremel.


You're certainly on the right track!
Over the years, the fixes have been to either add an extra hole in each 1/4 section of the hub, or else bevel or modify the existing ones. Today I mostly add some tiny vee-shaped grooves toward the upstream rotation direction to widen the capture zone of the oil film that is slipping around the inside of the hub. This has worked better than the 'extra-hole' approach on the 750, and it doesn't weaken the hub (important for the racers) at all. These grooves are barely .006" deep, cut with either a Dremel saw bit or grinder (flat) bit. I also rout away the tiny "dam" that always exists in the most-inner hole in the web of the casting (all the way at the back of the hub): this then creates a natural high-capture point of the oil. In the end, when I first did this last mod it REALLY improved the hot-release of the plates in the clutch, indicating that this is probably the very site where most of these clutches hang up when hot.

Hi Mark,

Do you happen to have a photo of this?  I have a K8 and haven't pulled the clutch apart yet, but I'm assuming the last of the SOHC production would have the "latest" holes Honda thought would work.  I am waiting for an o-ring at the moment, but I changed the oil pump o-rings and I'm swapping the 5 x 2.5mm on the shifter side for a new one, so the clutch is last bit to boost oil pressure.  In 95F heat in traffic I'm getting a low oil pressure light at idle, so I'm trying to fix that.

Thanks,
Randy

Here is another thread with pictures.  What oil weight are you running?

http://forums.sohc4.net/index.php?topic=78643.0
« Last Edit: June 22, 2016, 03:49:37 AM by 70CB750 »
Prokop
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Offline RandyBMC

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Re: Clutch Hub modification posts
« Reply #47 on: June 23, 2016, 04:09:40 PM »
10W40 initially, then 20W50 - still have the light. 

I have seen that thread too.  I was talking specifically about the grooves Mark mentions rather than the holes.

Thanks though!

Online scottly

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Re: Clutch Hub modification posts
« Reply #48 on: June 23, 2016, 05:50:58 PM »
I changed the oil pump o-rings and I'm swapping the 5 x 2.5mm on the shifter side for a new one, so the clutch is last bit to boost oil pressure.  In 95F heat in traffic I'm getting a low oil pressure light at idle, so I'm trying to fix that.

Thanks,
Randy
The clutch mods are to reduce clutch drag, and won't help with oil pressure. Sorry..
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Offline RandyBMC

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Re: Clutch Hub modification posts
« Reply #49 on: June 23, 2016, 10:11:09 PM »
From what I've read, the additional holes increase oil pressure at idle - in combination with the o-rings (which may be where the entire increase actually comes from).  Is this wrong?  I have no problem at all with neutral, clutch drag or shifting.

The 5mm x 2.5mm o-ring gets here tomorrow, so I can update if just the o-rings help.