The fall and rise of a works SFC engine
- Thread starter sfcpiet
- Start date
Laverdian
Senior member
- Location
- Brigadoon, Scotland
I could see slow progress being made when I delivered and collected other stuff to be repaired
FFS Piet, you mean my Drummer crankcases were ?test pieces??
Well, I?m sure when you?ve machined and dressed off the well repair areas the result will be every bit as impressive as the job you did on the Drummer cases.
Ian
FFS Piet, you mean my Drummer crankcases were ?test pieces??
Well, I?m sure when you?ve machined and dressed off the well repair areas the result will be every bit as impressive as the job you did on the Drummer cases.
Ian
piranha-bro2
Hero member
- Location
- Melbourne
That's quite an undertaking. Shame you lost your regular specialist, but it seems the new mob are pretty good at what they do too!
Are you gonna try and source some more of the same rods that were in it when this all happened?
Are you gonna try and source some more of the same rods that were in it when this all happened?
Piranha Brother 2 said:That's quite an undertaking. Shame you lost your regular specialist, but it seems the new mob are pretty good at what they do too!
Are you gonna try and source some more of the same rods that were in it when this all happened?
Ffs, no. Last pair of SFC Carillos is waiting. And the last pair of NOS Elettronica pistons. Rest is a walk in the park...
piet
breganzane
Hero member
- Location
- NSW Australia
(thumbup) (congrats)
piranha-bro2
Hero member
- Location
- Melbourne
I've got a new pair here - 80.0mm. For sale too.
Yogi
Hero member
- Location
- Bellingen NSW Australia
Really happy for you, Piet!
CLEMTOG said:
Clem,
The engine would originally have had the special narrow valve angle head with the special cams and rockers. And the special pistons to go with it.
When aquired, the engine was fitted with a elletronica head, barrel and pistons. All valves were bent because they had kissed the side of the valve cutouts in the piston crowns. Turned out the crowns were not correctly machined with the cutouts at about 80? to the cam axis. To me, this points to manually machined pistons, maybe prototypes for the elletronica? These pistons were re-worked with a Dremel and re-fitted. New NOS elletronica valves were also fitted.
I do know where a complete set, comprising of head, innards, barrel and pistons is, but the owner is somewhat reluctant to part with the stuff. Not even in a swap for the elletronica bits. So, I'll just have to put up with what I've got for the time being.
piet
Attachments
chrisk
Hero member
- Location
- Brisbane, Australia
Too cool 8)
piranha-bro2
Hero member
- Location
- Melbourne
Paul Marx said:
Not sure about that - but i do know they aren't really a good match. Lee used them in his SF and from memory it pinged pretty badly (even on leaded fuel back in the 70s) and on inspection had cracked between oil holes in ring lands and gudgeon - which would indicate a lot more than 5:1!!
Tippie
Hero member
- Location
- Dr?bak, Norway
High dome and a totally different squish system to all the other twins which have a flat squish band on the head and piston - very easy to set up to the desired 1mm. The angle on an elettronica head must relate to the outer edge of the piston as seen in the Piet?s pic. Many earlier engines (Duc single, many older cars) had this system, much harder to set squish.
I have seen numerous hard ridden SF pistons where the valve cutouts do not match the valve angle, with contact lower down in the cutout, maybe happened on valve bounce, they also needed a dremel job to avoid contact.
I fitted those electronica pistons with a 5C cam before I had learnt about correct setup. I really didn't like how they cracked between the oil relief holes in the oil ring groove and the gudgeon holes both sides of both pistons. Modified standard pistons for compression and squish work great in an SF.
Motor is coming along great Piet, excellent resurrection work.
If the owner of those bits is following - just let Piet have them, they will be going where they were intended in the first place.
I have seen numerous hard ridden SF pistons where the valve cutouts do not match the valve angle, with contact lower down in the cutout, maybe happened on valve bounce, they also needed a dremel job to avoid contact.
I fitted those electronica pistons with a 5C cam before I had learnt about correct setup. I really didn't like how they cracked between the oil relief holes in the oil ring groove and the gudgeon holes both sides of both pistons. Modified standard pistons for compression and squish work great in an SF.
Motor is coming along great Piet, excellent resurrection work.
If the owner of those bits is following - just let Piet have them, they will be going where they were intended in the first place.
CLEMTOG
Hero member
Piet, I see, I see of course I can see, eletronnica head because you don't have the EXTREMELY rare 73 head. what cam chain is installed? single or double?
who ever is hogging those bits, I hope he can also build a complete 73 motor, including alternator? otherwise, what the f**k!
CLEM
who ever is hogging those bits, I hope he can also build a complete 73 motor, including alternator? otherwise, what the f**k!
CLEM
mauricejota7604
Hero member
- Location
- Victoria Australia
Those rods aint gona snap Piet!!!
Been quite some time, but things have been happening!
After the welding, the case distortion was unfortunately not acceptable, almost 4mm warpage diagonally across the case mating surfaces when placed on the marking table. I had not expected this amount. This turned out to be quite frustrating, completely deflating my incentive to zero for a while. After a deal of researching, another flat-ground steel plate was sourced late 2023, lots of holes drilled and one after the other a case half was bolted to it and shoved into the oven for around 10 hours and 250° (all my oven can muster). After slow cooling, warping was already considerably less, but still out the ball park. A length of 90mm steel bar was transformed into a crankshaft dummy and the cases, bolted together with the dummy installed, went back into the oven again. After cooling, I simply let the assembly rest, over a year! I finally seperated the cases last September to find they had taken back their proper shape to within 0.5mm when measured diagonally across the mating surfaces, about on par with a set of old, used stock cases. The actual hardness of the alloy does not seem to have suffered. Pretty chuffed...
In the meantime, I had the chance to aquire a nice set of used Electronica pistons and barrel to suit, one less worry.
The upper case half is now with an engineering company to skim over the barrel base surface and re-drill/thread the stud bore. Hoping to recieve it back by the end of February. Ultimate goal is to have the bike runnning for the Nürburgring event in August.
Pics to follow when the case reurns.
piet
After the welding, the case distortion was unfortunately not acceptable, almost 4mm warpage diagonally across the case mating surfaces when placed on the marking table. I had not expected this amount. This turned out to be quite frustrating, completely deflating my incentive to zero for a while. After a deal of researching, another flat-ground steel plate was sourced late 2023, lots of holes drilled and one after the other a case half was bolted to it and shoved into the oven for around 10 hours and 250° (all my oven can muster). After slow cooling, warping was already considerably less, but still out the ball park. A length of 90mm steel bar was transformed into a crankshaft dummy and the cases, bolted together with the dummy installed, went back into the oven again. After cooling, I simply let the assembly rest, over a year! I finally seperated the cases last September to find they had taken back their proper shape to within 0.5mm when measured diagonally across the mating surfaces, about on par with a set of old, used stock cases. The actual hardness of the alloy does not seem to have suffered. Pretty chuffed...
In the meantime, I had the chance to aquire a nice set of used Electronica pistons and barrel to suit, one less worry.
The upper case half is now with an engineering company to skim over the barrel base surface and re-drill/thread the stud bore. Hoping to recieve it back by the end of February. Ultimate goal is to have the bike runnning for the Nürburgring event in August.
Pics to follow when the case reurns.
piet
Jo
Hero member
- Location
- Cologne, NRW Germany
Wow – this severe warping sounds like a really serious obstacle. Guess others had most probably throw in the towel and it’s quite understandable that you gave it a rest for a while. Seems your latest ideas, to a certain effort as it sounds, brought the progess req'd however. Great to hear that you've now got some grip on it again anyways. I'm curious to see how it continues!
