Ceriani 35mm - Fork Service

martymoose said:
Thanks for that info Marnix, so the 35's I've got are disc brake ones, assume same internals as the drums?
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That’s correct, contrary to my expectations. I have 2 of these 35mm disc brake forks and both have the drum brake type damper mechanism.

Marnix
 
With my 35mm Ceriani's on a 70 750SF0 BREV Drummer, I started with Belray 20wt (Literally rattled my teeth and skidded the front wheel out) - Went 15 wt then 10 wt not too shabby; however, I do recommend progressive springs for both the forks and rear Ceriani shocks ;o)

To save you headaches in the future, every year or 2 you should drain, flush and replace the fork oil and use a good fork boot like a Bates with a descent clamp.
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After all that work button her up properly - Service her every 2 years and you will never have issues with 35mm Ceriani forks for the rest of your life ;o)

All Italian Classic Motorcycles used 35mm Ceriani forks, Laverda, MV Augusta, Ducati, Bennelli, Moto Morini, Guzzi... etc.

F*^K a Moto Morini Heel/Toe shifter on Breganzie - Heaven forbid ;o)
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By the way you really can't put bigger pipes on a SF or an SFC then that.

You can do whatever you want to do with a 750SF as that's the way they were designed - Probably the 1st Cafe Racer offered to the Public. Plus they are easy to work with ! If you want to go over 120 mph down any straight - Breganzie you it with the 750SF back in 1970 with your Freedom Mods !

Really a light mono coupe frame back in 69 with a 7500 rpm S Model 750 SOHC Twin - Well ahead of her time - And still desrves respect to this day as she is still capable of winning the race. Absolutely a WOW History !

Say 10:1 Compression with a long duration cam - Note she never goes much above 7000 rpm but keep the momentum up on the track - Great Breganzie rider ;o)
I would not want that long duration cam for daily riding or for Cambrian Shield Racing. Notice that SF rider tends to go over 7000 rpm occasionally with that shorter duration cam but tends to hold back - What not !

That SFC has a terrible fairing in my opinion.

Cambrian Shield Racing is at least 300 to 400 miles where 1/2 of it is at night with a torrential down pour before you get home when the sun comes comes up.

Build your Breganzie 750SF to suit your style of riding. I did and I loved her for 45 years.

Of course I blew pistons and tore her apart numerous times but she was a die heart racer.

The 750SF may not be for everyone but she was My Ride and she never hurt me - A Hum ! Except for one incident were I dumped her in front of a Police Cruiser but that was under extenuating circumstances. I did limp awhile but never admitted it ;o)

Word of advise - If you run your Breganzie 750SF hard you should change out your valve springs every 2 or 3 years. Do not even think about shimming them. The harder you ride her the better she appreciates you to keep her in tune. That 7400 rpm Red Line isn't there for nothing and often she will go over that for hours on end if you love her enough.

To go further - Her Cast valves are rather heavy - You should consider replacing them with Manley Ultra Lights and replace the Valve Guides with Bronze and do a Grumpy Jenkings seat specs with slight porting below the seats into the bowl. Now you are at 8000 rpm ;o)
 
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Just to finish this off - I used 170ml of 30wt in each first and gave it a run, and it felt a bit solid, so drained it out (got 150ish ml out). Replaced with the 20wt and that seems fine, I only bought it earlier this year and is my first Laverda so no expert, but whatever was in there was a sludgy brown mess, and it all feels so much better, - once i'm used to it ill have a look at the springs I went with 10mm of spacers for now.

It's feeling like a different bike to when I bought it, to be fair I wanted a Laverda and it looked alright not enough science there, so ended up with lots of bodges by someone who clearly was partially restoring classic ornaments, and didn't care too much about safety or reliability...but with the help of many on the forum I've undone the bodges and fixed the major issues.

Engine / Timing / Mixture Sorted
Starter Clutch rebuilt
Front and rear drums rebuilt
Forks serviced
Rewired (inc. removal of household flex..) Everything now on relays.
Indicators I know some won’t like my CEVs but the work nicely.
And my favourite refurbing and fitting the Flamm horns I found in the US - can't beleive I bought an SF with a japanese made :ninja: horn the original is brilliant

Dare I ask what to do about the Koni rear shocks - do the originals ever come up for sale, the Konis are really solid!
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thanks all
franc
 
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Hi Franc
I usually find it better to start with light oil, and go heavier, up to the point where fork control becomes acceptable. Ensuring maximum compliance, whilst having damping control. Quite difficult with the 35mm Ceris though as, in my opinion, the balance between compression and rebound damping is not great in stock form.
 
Good work sorting the beast, Franc. Sounds like you had your priorities right. I thought 30wt sounded a bit on the hypoid gear oil spectrum!

I did some major engine work on an SF1 and was then asked to fit it to the frame and get it registered. First ride the front end felt like it was rigid - pulled off a fork cap and found oil to the top - there were many many more 'issues' uncovered in the time I worked it into rideable shape - DPOs are capable of absolutely anything!
 
Franc said:
Dare I ask what to do about the Koni rear shocks - do the originals ever come up for sale, the Konis are really solid!
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They shouldn't be, if correctly sprung for your bike. Genuine Konis could be rebuilt back in the day, and Ikon are very similar so service parts / alternative springs may be available.
 
The Koni shocks are Koni not ikon when I bounce on the bike (I’m 112kg ) I get max 5mm drop with the spring preload at lowest setting, they are in immaculate condition and are the correct one As stated at the time for an SF. They are just way too hard maybe faulty..?
 
Take one shock off at a time and try your bounce test again. Maybe one is faulty or bent?
If they both are the same then somebody previous has thought harder springs meant better suspension.

Actually, before you do that… is your chain too tight?
 
I’ll try that maybe one is faulty have never taken them off or experimented individually I’ve got 30mm of play in the chain and I checked the swing arm was free this morning I thought that could be the issue.
How’s Auckland going we lived at Northcote Point till 2009 - miss the fishing!
Franc
 
Auckland’s still growing, too much traffic, too expensive, etc etc. Like any other city I guess!
I haven’t been fishing since my mate rolled the Land Rover coming back down Muriwai… we were fine but he broke my good surf caster 🤨
 
I've ridden on Konis and they are pliant and work well. I fitted them to that SF1 I mentioned above (that had the forks filled to the brim with oil) so I could get it registered - the Marzocchi Stradas that were on it were seeping but were like riding on solid steel rods by comparison with the Konis.

Don't mix up ride height adjustment with spring rate either - the adjusters will lift the bike but have zero effect on spring compression rate. If the dampers are functioning OK you need softer springs.
 
Do your Konis have the 4-way damping adjusters below the rubber cover at the top of each shock. Check to see what number they are set too. Icon has available 2 springs std and heavy-duty for shocks they supply. Identifying your springs from those two, or even if you have something really odd takes some trouble, I have had springs identified at spring makers where they have gadgets that compress and log the load that takes but finding someone to do that isn't easy. BTW Icon in OZ are exact Koni replicas, they bought the Koni Manufacturing gear when Koni stopped building bike shocks so all pats are available from them. I don't like the multi-rate springs Koni and Icon use, I don't pillion so I had Icon make straight rate springs to suit my weight, that worked out well. BTW that one shock test is a great idea, and will as you say check for a load of issues.
 
MarnixSFC said:
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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Just annotated this hidden forum gem in my Green Book where this isn't mentioned -my seals are leaky and and it needed fresh oil anyway. Thanks :)
 
Does anyone have the size of the 35mm fork seals handy?
Once I remove the wheel and sliders the 750 stands mightily in my way cluttering up the shed so I'd like to get it rolling again as soon as I can and having oil and the seals at the ready would help :)

Green Book doesn't mention sizes and my search-fu here comes up empty.

Thanks in advance!
 
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