Topic: Clutch questions with pictures

[britman]

Ok, here I go again where I need someone with a lot more knowledge than me to give an opinion.  On my 74 project bike I pulled the clutch today for symptoms of a hard to find neutral, extremely noisy basket at idle, and grabbing.  The discs are not that bad, about 3.4mm per unit and metal plates show no burning and just need a good clean. The first surprise came when I pulled the springs and found four thin washers under the base of all four.  I checked the old springs with the new OEM set I purchased and they appear to be too short, my theory, the washers were an attempt to compensate for wrong size springs? Next, upon inspection I find two stress cracks around the base of two of the spring posts, they still appear solid, but I would like an opinion as whether or not you would replace the pressure plate. I am becoming more and more convinced this project bike was formally owned by Satan, or at the least, one of his real close relatives.  Thanks in advance for any input guys.....

[BenelliSEI]

I’d agree with your guess on the springs being incorrect. Assuming the new ones are correct (see the free length chart I’ve attached), those are way too short. Did the clutch slip? Your friction disc measurement looks “like new”.

Regarding those stress cracks: they will only get worse….. I’d replace it.

[Kelly E]

I think the thin washers are to keep the hard steel of the springs from digging into the soft aluminium but they do look like an odd assortment of washers. How thin are they? I'm with Benelli, replace the pressure plate before it fails while riding.

[newday777]

Here's a thread on the cracking pressure plate

http://forums.sohc4.net/index.php/topic,192661.msg2245999/topicseen.html#new

[HondaMan]

That pressure plate is doomed.
There is a [malicious] vendor out there who is selling extra-strong springs with shim washers for these clutches as his "upgrade". I have seen both slant-cut cork plates and square-cut cork plates from him. Are yours square-cut corks or are they the slant-cut ones?

An unsolicited comment:
Since the OEM clutch will handle over 90 HP, there is no good reason to "upgrade" these clutches until you reach the HP levels like PeWe has in his bikes. Heck, even Dick Mann rode a stock clutch at Daytona 1970 with just some shimmed OEM springs (85 HP engine). At most, some of the later ones with the dual-steel 'slipper' plates can be improved (to stop rattling noises at idle, and extended slip during hard takeoffs) by removing the dual-steel plate and installing a thicker bottom steel plate (from the 1979 GL1000/1100 bike).

[britman]

The thin washers are an assortment and miss-matched.  I believe one is spark plug washer.  In the parts schematic I did not see them displayed.  I have done a quick search for another pressure plate, apparently they are not that many around, probably due to the same problem I have. 

[HondaMan]

At the least, have someone run beads of weld along those cracks.

[MauiK3]

Many “upgrades” just aren’t.

[britman]

I bit the bullet and bought the only used one on eBay at the moment.  Looks like pork and beans and vienna sausage on the menu for awhile, apparently they are few and far between and the seller knew it. It has been a real quest to bring this one back around, I am really at the point I just want to see it go out the door, move along, no profit to see here.  I swear the next one for the winter months is going to be anything but another 750K. 

[scottly]

The short springs are from a late clutch, with a deeper basket and the double-steel disk. I used the shorter K7 springs in my K1 clutch with 1/8" thick washers as shims, IIRC. I documented it here somewhere on one of the long running clutch threads??

[PeWe]

I got washers with an aftermarket heavy duty clutch in the 80's.
It had +1 fiber and 1 metal disc. Thinner fibers.

I saw that the early CB750 had washers under the springs.
CMS -69 chart.

I have had thoughts about that part with those weak looking towers for springs. Does not look strong enough.

I did not break any in my K6 with 836cc 80Whp.
Now 970cc, last dyno soon 1 year ago 107.5Whp DIN.
Carbs got correct needles after that so it runs better. Maybe not at top power 8000-9500rpm.

F2 clutch with double metal disc and extra hard Barnett springs. For CB550 and the smaller.
It slips with std Barnett for CB750 despite glass beaded metal discs.

The outer part with bearing is a stronger billet type.
But those towers still stock weak looking type.

Can a PO had assembled clutch wrong so the bottom part does not fit into the splines?
50% chance to get it wrong if not verified at assembly. Tighten clutch when wrong can crack it?

Good to test first and use marker pen on one tower and beside the hole it fits.

Barnett springs are longer. Almost 37mm.
Measured 36.9mm golden spring. Has been used during one ride where I got sudden slip after 3000rpm, before 4000 on 3rd gear. 17:48 gearing. Felt like sudden wheel spin. Earlier this year when I thought std Barnett should due.

Black, the stronger 66 lb model, gold CB750 56 lb

I lubed clutch cable that helped my office working  hand to handle those hard springs during a longer ride with frequent use of clutch.

[flybackwards]

I just replaced the clutch assy on my K1 - it would not disengage enough to shift properly and the lever effort was hugh. What I took out looked like a collection of junk and I swear it looked like valve springs and shims on the posts. Nothing damaged or cracked though. I replaced it with a four plate unit from CycleX and it now works very well with a manageable lever input.