Ceriani 35mm - Fork Service

Franc

New member
Location
UK - Midlands
Morning
Could someone please advise on the steps to servicing / oil change the 35mm SF forks, lots of conflicting info about..I have some 30wt oil which is apparently the go for the 35mm ceriani forks? (There again as the operating manual says use Shell Tellus 33 that’s more like 20-25.)

I have the front wheel off,
the top caps removed - new o rings ready
forks are fully extended
Drain screws removed - new copper washers Ready
oil out - have flushed / pumped through with some fresh oil all clean in the pan

do I just put the drain plugs in, pour 170mm in each fork and reassemble? Having seen people with syringes, plastic tubes and measuring devices I don’t want to miss out..

your help appreciated as always

franc
 

Vince

Hero member
mm are a distance dimension. There are 2 ways to set fork oil, quantity that being volume, cc or millilitres and that's listed in the manual or air gap. That's the high of oil measured from the top of the fork with the fork fully jacked-up, compressed with the springs out and that's in mm usually between 120 to 160mm. It must be the same in each fork. The way I do it is with a trolly jack under the front wheel with the bike on the centre stand and a cable tie on the front brake lever. Don't jack it too much or it will fall off the stand. You need to pump the forks up and down a few times to remove any trapped air before measuring the oil lever. I set the level using a turkey baster to suck the oil out. Do I need to describe what a turkey baster is? Do some googling to see pics of this on the web, it's hard to describe all the processes in detail.
BTW it's either 10wt or 15wt fork oil, in my experience any thicker won't help. And use proper fork oil, its approx $20 and cheap enough not to bother using anything else.
 

martymoose

Hero member
Fork oil has anti frothing agents, when you think about it, on a bumpy road, that oil is working a lot. Used to use 15 weight, gone to 10 weight now, I think Red uses 7.5. Carlo is world expert on ceriani rebuilds, he should be along shortly....
 

Vince

Hero member
Might I point out my 10,000 post thread about this subject.
 

Vince

Hero member
NO NO NO I was just the idiot who tried some adjustments and documented what effect they had. And what started it was me asking what effect would happen if I drilled another hole in the emulator high-speed compression plate and was told to do it and see. So I did.
 

natm

Full member
Location
Bushmills
30w sounds too heavy. My SF3 came to me with 35mm Ceriani forks which were very hard and gave a harsh ride. I fitted progressive springs and 10w oil. Still a firm ride but a big improvement.
 

Vince

Hero member
I eventually found some hard plastic clear tube that I stick up the turkey baster end that gets a better way to get consistent oil suckage to the level I wanted, is that a word Motion Pro sells professional gear to do this.
 

MarnixSFC

Hero member
Please note that the drum brake 35mm forks and the 38mm disc brake ones have nothing in common construction wise, other than that they were made by Ceriani. The 35 needs a much thicker oil to work well (in 20-30W range approximately ) than the 38 forks (in 5 to 15W range approximately).

Marnix
 
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Franc

New member
Location
UK - Midlands
Thanks for the info so far - decided to get a proper look inside the forks do the fork seals etc. I’ve got the wheel off so might as well go the extra hour - As per the photos everything looks intact the bores are smooth- but I’m no expert Will I clean and polish everything up and reassemble? Or is someone going to tell me the bits shouldn’t look like that and it’s open wallet surgery time again withDoctor Laverda! The springs are exactly 18 1/2 “ / 172mm anyone know what they should be?

thank you all.


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piranha-bro2

Hero member
Location
Melbourne
I wouldn't go any further than new seals and make sure it's nice and clean before reassembly. On my SF1 I used to use 15 or 20wt fork oil from memory, and 170cc. They work so well it's not really worth going down the mm (air gap) method - in my opinion. I did used top add about 10mm alu spacers above the springs before fitting the caps - but that just gives you a bit less sag.

Definitely don't recall ever using 30wt - you don't want to kill the nice responsive ride these forks give.
 

Franc

New member
Location
UK - Midlands
Thanks for that - i think the spacers are a good call These springs are going to have lost a bit of bounce in 40 years I had a quick look for some new ones but most stuff out there is for 38s. I’m for sedate riding not ‘chin on the speedo’, as long as it’s maintained and safe I don’t need to get setup with progressive springs.

time for a beer
 

piranha-bro2

Hero member
Location
Melbourne
Enjoy that beer! In the 30 years I rode on my 35s I never sensed the springs softening out, but did notice a deterioration in very high speed damping, understandable if you consider general wear in the internals. Never dangerous though. I even converted them to disc by fitting legs from a 35mm disc brake model. Brilliant forks for their age.
 

martymoose

Hero member
Thanks for that info Marnix, so the 35's I've got are disc brake ones, assume same internals as the drums?

I'm working on a club member who has a GT that has sat for 40 years with a smashed front end. Hopefully he weakens before I'm too old to fix and ride it......
 

Franc

New member
Location
UK - Midlands
All clean and back together just waiting for the oil - ordered 20 and 30wt same brand, thought i'd experiment and make up some 25wt with equal quantities first, I can go harder or softer from there ... great opportunity to mess about for a few hours, and embrace all the opinions on what weight fork oil works in 35s

Thanks
 
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