74 CZ Dry Clutch! How much oil?

[Kenneth S (222)]

Hi Tech Buffs,
The 74 CZ my mate Jon bought was leaking oil so we pulled the clutch cover and left case off to check the gasket of which there wasn't one! After searching around and deciding finding one was too big an ask, we made our own and began the reassembly last night. I had heard the term 'dry clutch' before but only having owned Japanese dirt bikes in my time, I hadn't actually seen one. Looking at this, I assume this is one. The clutch basket is sealed from the inner gears.

My questions are:

Is this what is commonly known as a dry clutch? If so I thought there would be no oil.

When we dis-assembled it, there was a layer of oil through the plates, how much oil is the right amount to put in when re-assembling?

And for my own knowledge bank, why bother, what are the benefits of a clutch like this over whats in my CR250?

[Lozza]

Think the term dry clutch might give a small hint  . A dry clutch looses less HP but has a very on/off style of take up, more used on road racers. The CZ would be the only dirt bike with a dry clutch.

[firko]

It may have been converted to wet clutch operation. The CZ chaps will know the guff.

[Canam370]

Most likely the seal behind the clutch is leaking so it'll be tranny oil your seeing. Not hard to replace the seal if you want to. The oil wont worry the plates. Contrary to popular belief the CZ dry clutch isn't like a light switch in action and they are very robust.

[VMX60]

Looks to be a dry clutch so large inner case  seal leaking or the small oring behind the outer plate as shown in your photo has been left out when assy

Can supply sizes if required or take them to your local bearing service with samples

Std CZ gearbox oil qty 650cc

Cheers

[firko]

Contrary to popular belief the CZ dry clutch isn't like a light switch in action and they are very robust.

I agree C-A, I reckon the CZ has one of the better clutches from the era. Maico however...that's another story.

[tony27]

Change the seal & o-ring & all will be good, if you get carried away you can also replace the o-ring on the clutch gear while you're in there
CZ's only need the clutch used twice during a race anyway, once to get off the line & the other to stop you running into the back of the ute back in the pits

[Kenneth S (222)]

Thanks guys

[Kenneth S (222)]

Hi Guys, Well we have this thing running nicely now. The only question I have that one of you CZ enthusiasts might know is this. On the left front case of the engine is what I believe to be the oil level screw. Poor the gear oil in and when it runs out this hole, the oil level is right. The only thing is it only takes about 2-300cc of oil to get to this level. Yes I've checked for air locks, shaken it about etc but that's all it needs to get to that level, the screw is quite low on the cases. I figure it is because of the dry clutch, the cases only need enough oil sloshing around in the bottom of the gear box to lubricate the gears. Seems reasonable, yes?! It would be good though if there was someone with experience on these models out there who could confirm I am on the right track.

[tony27]

The reason you can only get 200-300mls out is that the rest is in the primary drive cover & doesn't drain unless you either lean the bike over with the screw in the sidecover out or lie it the other way so it drains back into the gearbox
The hole that connects the gearbox & primary drive is quite high up behind the riveted plate between the crank & gearbox input shaft

[Noel]

Hi Ken,
Yeh what he said, (tony 27)
from dry you should get at least 600 mm in.

ps. if you have trouble with more oil leaking into clutch "Serco" have fibre plates that can run wet or dry

pps wil this bike be on the Heaven grids this year?

Noel

[Kenneth S (222)]

Thanks again guys, No Noel, I am trying to convince Jon my business partner who rides it and is a beginner that at Heaven we are even tempered, measured and careful riders so he doesn't have a thing to fear mixing it up with us. He doesn't believe me though!!

[Canam370]

ps. if you have trouble with more oil leaking into clutch "Serco" have fibre plates that can run wet or dry



The fibre plates are made by Barnett. I've used a set for a couple of seasons with great performance. The bit of oil which inevitably reaches the plates doesn't effect them. I purchased a spare set which at this point has been a waste of money!