SFC 750 swingarm on a triple, whos' done it?

P

paulincayman

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Cayman Islands
So once again I've leapt in feet first , randomly bought a SFC etc 750 swingarm for my 77 3CL project , I'm fitting GSXR1100 wheels with a 140 already purchased, thought it might give me a bit more space over the stock swinger for the tire. I took some measurements and it is pretty much the same as the stock unit except for being about an inch shorter between front pivot and rear axle and therefore the shock mounts are an inch closer forward also. I would welcome input from anyone who has done this mod with regards to shock length and maintaining the stock geometry, I have not bought new shocks as yet
, so maybe also an an opportunity to tweak the geometry? ( no offence intended). I hate guesswork especially with the shipping costs..all comments welcome
Second point ,
It looks like the swinger has bonded rubber bushes in the pivot tube with metal bushes into those, the OD of the tube is the same as the stock 3cl item, so I'm optimistically assuming the guts are interchangeable having recently purchased the needle roller bearing kit for the stock item
, is that correct or am I in for more grief as usual?
Paul
 
If your 750 swingarm is shorter than that of the triple, quite likely you've picked one from a very early GT. This lacks the front brace, about 3cm length, RH wheel spindle slot wider than LH and is weaker at the wheel mounts (8(?)mm vs. 10mm thickness). Also quite certain the SFCs had either bronze bushes or needle bearings in the pivot. At least the later SFC swingers had rearwards shifted shock mounts, aft of the wheel spindle.

So you're aiming for a stiffly-suspended, short-wheelbase bike that will snap off the swingarm ends due to greater forces induced by modern wide rubber?

Stock SF1-3 swingarms are the same length as the triple type. The drum brake type are not plug-n-play for a 3CL because of the differing wheel spindle slots, disc braked SF3 used the stock triple swinger.

One consolation, your recently purchased needle bearing kit will fit... after a lot of effort and swearing while removing the rubber bushes.

Imho, if my assumption is correct, you dived in head first, into an empty pool. ;)

piet
 
Have to agree with Piet, Paul - you were led astray believing this was an SFC swinger. I see Eflay listings that often quote a Lav part as fitting EVEERY laverda ever made.

I sold my SF1/2 swingarm to Tom (Ozjotati), who will chime in once he's up and about here in Oz. Straight swap as Piet points out, with a simple sleeve required for the larger RH axle slot that accommodated the quick-detach cush assembly on those models. I used it with a Kwaka Z disc rear hub and 20mm axle and had a frame mount torque arm, but they are easy to fit in any guise you like.
 
Hi Paul, I’ve done this on my Jota and all went reasonably well.one issue was the pivot bearing recess was too deep and I had to use three or four spindle shims to pack it out to the correct dimension. The caliper bracket attaches to the original fixing point on the swingarm. You will as Quentin said need to make a spacer for he ‘rhs` axle slot to accommodate the different diameters there. Apart from that it should be an easy fit😀. But when you change one thing it generally leads to other problems occu 🙁. In my case I run a Zane rear caliper and bracket and also run the Zane axle which required filing the ‘lhs axle hole in the swingarm to 20mm.
Apart from all that it was a good modification as allows me to run a 150 rear Tyre😀. Look forward to hearing how you get on.
Caio Tom
 
piranha-bro2 said:
Have to agree with Piet, Paul - you were led astray believing this was an SFC swinger. I see Eflay listings that often quote a Lav part as fitting EVEERY laverda ever made.

I sold my SF1/2 swingarm to Tom (Ozjotati), who will chime in once he's up and about here in Oz. Straight swap as Piet points out, with a simple sleeve required for the larger RH axle slot that accommodated the quick-detach cush assembly on those models. I used it with a Kwaka Z disc rear hub and 20mm axle and had a frame mount torque arm, but they are easy to fit in any guise you like.
Click to expand...
Yeah, just like all 750s are SFCs, all triples are Jotas... caveat emptor. :rolleyes:

piet
 
sfcpiet said:
If your 750 swingarm is shorter than that of the triple, quite likely you've picked one from a very early GT. This lacks the front brace, about 3cm length, RH wheel spindle slot wider than LH and is weaker at the wheel mounts (8(?)mm vs. 10mm thickness). Also quite certain the SFCs had either bronze bushes or needle bearings in the pivot. At least the later SFC swingers had rearwards shifted shock mounts, aft of the wheel spindle.
Click to expand...
Just to add to the confusion,, the ( Early GT )swing arm that I bought is shorter than the 3CL.... but it has all the same bracing at the front and the rear axle plates are the same thickness as the stock item ... mysteries from Breganze,,,
 
Well that's the question that started the thread..full circle.. Being shorter it would need shorter shocks to maintain the original geometry..and off we went..
once I discovered there was a longer alternative , which I have now purchased , the question became moot..
So now I have two spares to play with..perhaps build a monoshock swinger too.
 
paulincayman said:
Well that's the question that started the thread..full circle.. Being shorter it would need shorter shocks to maintain the original geometry..and off we went..
once I discovered there was a longer alternative , which I have now purchased , the question became moot..
So now I have two spares to play with..perhaps build a monoshock swinger too.
Click to expand...
I thought the prob was lack of a cross brace and thinner steel flats at the axle section? Still interested to know how much shorter - and how much the shock mount to pivot point varies.
 
paulincayman said:
Approx 3 cm / 1 1/2 ".

And I don't have a chain yet. :)

But I will be using the SF swinger. Same length as 3CL.
Click to expand...

I’d recommend a DID 50 ZVM X ring. My last one did over 20,000 miles. Compared to the mileages chains gave, back in the ‘70s, this one took less adjustments, in its life, than original ones needed in a weekend.
 
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