chrisk
Hero member
- Location
- Brisbane, Australia
Bugger, too nice to be covered up, where do we place the window in the crankcase?
Rome wasn't built in a day ..........................
750 crank balance factors
- Thread starter redax5
- Start date
Bugger, too nice to be covered up, where do we place the window in the crankcase?
Rome wasn't built in a day ..........................
Rockitdoc
Hero member
- Location
- Fort Collins, Colorado
redax5 said:here you go Chris, one of these is indeed your crank, be the one with the corroded ends
2 x 0/270's and 1 x 0/284 cranks, +/- 10 mins
be heading in to get balanced Monday, then back to get conrods installed, be glad to see the end of them, burnt some serious time doing these cranks
not a 5 minute job by any means
Red,
I tried sending a PM but the forum says I need to register to do this, which I have. I dunno. Anyway, I would like to obtain some Mikuni 36's for my RGS1000SFC and I hear you can fix me up. If true, send me an email or give me a call. Thanks, Scott scott.shuler@colostate.edu 1-720-289-2153
Yogi
Hero member
- Location
- Bellingen NSW Australia
drikko said:
Thanks for that mate....
chrisk
Hero member
- Location
- Brisbane, Australia
Hey Yogi
Are you the Andrew that bought the siver Mirrage in Melbourne in about 1989, via Greg Parish??
Are you the Andrew that bought the siver Mirrage in Melbourne in about 1989, via Greg Parish??
Dellortoman
Hero member
- Location
- Tasmania, Australia
G'day Chris. Are you thinking of Andy Carberry? He's got a silver mirage and lives in Melbourne.
Yogi
Hero member
- Location
- Bellingen NSW Australia
chrisk said:
Hi Chris,
No, that's not me.
chrisk
Hero member
- Location
- Brisbane, Australia
Dellortoman said:
Yep, that's the one, Thanks.
Cosi
Hero member
- Location
- Kingscliff
Just for the record his name is Antony, and he hates being called Andy.... Ants hes cool with 
chrisk
Hero member
- Location
- Brisbane, Australia
Cosi said:Just for the record his name is Antony, and he hates being called Andy.... Ants hes cool with
Bugger, I should have remembered that ........... bet he still listens to "A - - A - - A - - A - - Ant Music".
piranha-bro2
Hero member
- Location
- Melbourne
Howdy strangers. I'm the Quentin mentioned somewhere in this long thread (and mentioned in rabid tones SEVERAL times by Signor Motodrobb in various other threads on this site for my theft of his (spare!) crank centre . I'll be pulling that out and sending it back to you very soon, Rob ... only had it since '76!).
Have been following the conversation on SF/SFC crank twisting and balance factors with intense interest, having sweated and toiled to mod my SFC crank to 270 deg some time in the mid 90's ? I think it was the first Lav twin twist job in Oz. I certainly had very little to fall back on when I did it; internet was something to do with fishing, forum was a place in Rome.
I went down that path after reading of a guy on the NSW sth coast who did it to a BSA 650 twin that he crammed into an RGV frame! Vibration has been the ONLY thing I never really came to terms with on my beloved, so the idea of inbuilt counterbalance coupled with increased torque from the max piston speed offsetting top-/bottom-dead of the converted crank was the sealer.
Determining a balance factor may as well have been throwing a dart at some numbers and going with it - I managed to contact the Beezer man and he'd balance the old Brit to 50% ... and that's what I did. As for knowing what my SF1 or the SFC crank I inherited from brother, Lee (Tippie), I had absolutely no idea. I do know that virtually every SF I've ridden has distinctly different vibe characteristics, some pretty bloody awful, some tolerable, some very smooth - naturally, other factors such as engine condition and mods affect this, but some just seem to have been bad from the day they left the fabbrica in Breganze. My SF1 was truly buonissimo, especially after I did its first top end reco at about 110,000km (ran it without air filters for a year in the top end ... the geographical variety ? nooo, no dust up there! ... that was clever :-\). At some stage several years later a German moto mechanic who I worked with at Hartley Motorcycles in Perth, and who should have known better, convinced me the mains were sloppy and unbeknowns to me, damaged the crank centre while trying to press it apart; long story, but after throwing a cam chain in the middle of the Nullarbor in 1976-77, Motodrobber's crank centre entered the pic.
Back to twisties ... Red (beautiful work you do, by the way), I see you've sussed the preferred config, with the RH side advanced. I came to that conclusion figuring that the side farthest from drive needed the shorter interval in order to reduce the stress through the centre; this is demonstrated clearly at idle where the firing pulse from the RH cylinder is noticeably weaker than the big bang from the LH drive side that's waited 450 deg to do its thing. Also recall Tippie?s comment on the Norwegian he knows running at 90-630 firing intervals ? and broken crank centres.
I won't horrify anyone by describing my modus operandi as a 'home crank balancer' ? other than to say steel rulers make pretty good knife-edges. Suffice to say it was acceptable when it ran, but not what I could compare to any good V-twin or a TRX (which has counterbalancers). Up to 6k I'd say it was pretty bloody good, but a ride day at the Island showed up its shortcomings at higher rpm; this is complicated because I also believe sloppy main bearing journals in my very high-mileage cases and possibly less than ideal big end clearances may have exacerbated the hi-rpm vibes.
I went for 50% as I wanted to reduce the weight contributing to the rocking couple. I haven't run the bike for over ten years (a family came along and changed my priorities!), but that rocking couple has been the focus of endless hours of thought. Trying to compare the twisted Lav twin to a Brit twin is meaningless because the latter has a very narrow overall crank width, with a single flywheel squeezed between two mains - I'd guess the overall width of the outer webs on an SF/SFC would be close to double that of the Brit, the latter consolidating all its balance mechanism in a central flywheel. If/When I ever find time, I have a wild idea of neutralising the outer webs on the SF/C (balance factor 100%) and experimenting with using the centre webs for all balance duties - I'd also be going lower rather than higher in factor. Would certainly benefit from some of Red's fabulous jig pressing kit and outsourcing to balancing experts if I do ever find the time.
As far as performance, with nothing further done to the motor from when it ran at 360 (SFC crank, SFC valves & springs, 5C cam advanced 10 deg, ported and shaved head and thin base gasket to give 10.5:1 with swish-modified std SF Mondials), low-mid range power was the huge plus and the noise when I first fired it up literally made the hair on the back of my neck stand on end; it's not like any V-twin I've ever heard. I certainly lost something from the tuned pipe that worked so well with the 360 deg motor and 5C cam, especially if I could ever run it straight into the SFC reverse cone (noise? Sorry, can?t hear you ? did you say noise?). I?ll be looking into a different exhaust system, probably twin pipes, to try and regain the top end I feel was lost (maybe that?s an illusion??). Brother Tippie says his Scandinavian Post Classic 270 deg racer has ample top-end (runs a 6C cam and custom 2/1 that is quite different from the factory SFC 2/1). He also says hi motor smooths out at revs ? and from memory he followed my lead and balanced to 50%. Obviously anyone going down the twistie path would taylor their mods to the type of bike they want ? a full-blown race bike, a lively road sprinter/fast sports tourer (me), or an all-rounder.
I had some email contact with Steve Elliott (half of Palmelli) a decade or more ago and he?d twisted a stock SF without doing anything whatsoever to the crank balance ? he said it handles like a true gem, but you?re hard pressed to cover more than a few laps due to the awful vibes. They run their motor in that super-light frame and I suspect light frames and SF twins may not necessarily be a good combo (is that why Breganze built the SF frames from recycled water pipe? ;-). Perhaps Steve B can contradict me there, if his superlight SLC is any indication?
I?d better get off this keyboard! Before I do, as an afterword I later twisted a stock SF2 with splined centre to 88 deg, balanced to 60 or 65% from memory (I tapped threads into the balancing holes so I could add/remove weight via M10 grub screws by only removing the barrels). To my mind it shook pretty badly, but I am yet to get around to removing some of the weight to bring it down to 50% (and the owner also embraced family life and the Lav sits on blocks gathering dust!). From that point of view, an SF crank is a much easier proposition than and SFC due to the hardness of the latter. Man those webs are hard (especially the centres with incorporated crank pins!).
Christmas has come and gone and the last post I see on this topic is from last October, so surely there is some action to write about, real-world reviews, track tests? Would love to hear more about this and especially how the experimental balance factors turn out.
Thanks for reading.
Piranha Minore
. I'll be pulling that out and sending it back to you very soon, Rob ... only had it since '76!). Have been following the conversation on SF/SFC crank twisting and balance factors with intense interest, having sweated and toiled to mod my SFC crank to 270 deg some time in the mid 90's ? I think it was the first Lav twin twist job in Oz. I certainly had very little to fall back on when I did it; internet was something to do with fishing, forum was a place in Rome.
I went down that path after reading of a guy on the NSW sth coast who did it to a BSA 650 twin that he crammed into an RGV frame! Vibration has been the ONLY thing I never really came to terms with on my beloved, so the idea of inbuilt counterbalance coupled with increased torque from the max piston speed offsetting top-/bottom-dead of the converted crank was the sealer.
Determining a balance factor may as well have been throwing a dart at some numbers and going with it - I managed to contact the Beezer man and he'd balance the old Brit to 50% ... and that's what I did. As for knowing what my SF1 or the SFC crank I inherited from brother, Lee (Tippie), I had absolutely no idea. I do know that virtually every SF I've ridden has distinctly different vibe characteristics, some pretty bloody awful, some tolerable, some very smooth - naturally, other factors such as engine condition and mods affect this, but some just seem to have been bad from the day they left the fabbrica in Breganze. My SF1 was truly buonissimo, especially after I did its first top end reco at about 110,000km (ran it without air filters for a year in the top end ... the geographical variety ? nooo, no dust up there! ... that was clever :-\). At some stage several years later a German moto mechanic who I worked with at Hartley Motorcycles in Perth, and who should have known better, convinced me the mains were sloppy and unbeknowns to me, damaged the crank centre while trying to press it apart; long story, but after throwing a cam chain in the middle of the Nullarbor in 1976-77, Motodrobber's crank centre entered the pic.
Back to twisties ... Red (beautiful work you do, by the way), I see you've sussed the preferred config, with the RH side advanced. I came to that conclusion figuring that the side farthest from drive needed the shorter interval in order to reduce the stress through the centre; this is demonstrated clearly at idle where the firing pulse from the RH cylinder is noticeably weaker than the big bang from the LH drive side that's waited 450 deg to do its thing. Also recall Tippie?s comment on the Norwegian he knows running at 90-630 firing intervals ? and broken crank centres.
I won't horrify anyone by describing my modus operandi as a 'home crank balancer' ? other than to say steel rulers make pretty good knife-edges. Suffice to say it was acceptable when it ran, but not what I could compare to any good V-twin or a TRX (which has counterbalancers). Up to 6k I'd say it was pretty bloody good, but a ride day at the Island showed up its shortcomings at higher rpm; this is complicated because I also believe sloppy main bearing journals in my very high-mileage cases and possibly less than ideal big end clearances may have exacerbated the hi-rpm vibes.
I went for 50% as I wanted to reduce the weight contributing to the rocking couple. I haven't run the bike for over ten years (a family came along and changed my priorities!), but that rocking couple has been the focus of endless hours of thought. Trying to compare the twisted Lav twin to a Brit twin is meaningless because the latter has a very narrow overall crank width, with a single flywheel squeezed between two mains - I'd guess the overall width of the outer webs on an SF/SFC would be close to double that of the Brit, the latter consolidating all its balance mechanism in a central flywheel. If/When I ever find time, I have a wild idea of neutralising the outer webs on the SF/C (balance factor 100%) and experimenting with using the centre webs for all balance duties - I'd also be going lower rather than higher in factor. Would certainly benefit from some of Red's fabulous jig pressing kit and outsourcing to balancing experts if I do ever find the time.
As far as performance, with nothing further done to the motor from when it ran at 360 (SFC crank, SFC valves & springs, 5C cam advanced 10 deg, ported and shaved head and thin base gasket to give 10.5:1 with swish-modified std SF Mondials), low-mid range power was the huge plus and the noise when I first fired it up literally made the hair on the back of my neck stand on end; it's not like any V-twin I've ever heard. I certainly lost something from the tuned pipe that worked so well with the 360 deg motor and 5C cam, especially if I could ever run it straight into the SFC reverse cone (noise? Sorry, can?t hear you ? did you say noise?). I?ll be looking into a different exhaust system, probably twin pipes, to try and regain the top end I feel was lost (maybe that?s an illusion??). Brother Tippie says his Scandinavian Post Classic 270 deg racer has ample top-end (runs a 6C cam and custom 2/1 that is quite different from the factory SFC 2/1). He also says hi motor smooths out at revs ? and from memory he followed my lead and balanced to 50%. Obviously anyone going down the twistie path would taylor their mods to the type of bike they want ? a full-blown race bike, a lively road sprinter/fast sports tourer (me), or an all-rounder.
I had some email contact with Steve Elliott (half of Palmelli) a decade or more ago and he?d twisted a stock SF without doing anything whatsoever to the crank balance ? he said it handles like a true gem, but you?re hard pressed to cover more than a few laps due to the awful vibes. They run their motor in that super-light frame and I suspect light frames and SF twins may not necessarily be a good combo (is that why Breganze built the SF frames from recycled water pipe? ;-). Perhaps Steve B can contradict me there, if his superlight SLC is any indication?
I?d better get off this keyboard! Before I do, as an afterword I later twisted a stock SF2 with splined centre to 88 deg, balanced to 60 or 65% from memory (I tapped threads into the balancing holes so I could add/remove weight via M10 grub screws by only removing the barrels). To my mind it shook pretty badly, but I am yet to get around to removing some of the weight to bring it down to 50% (and the owner also embraced family life and the Lav sits on blocks gathering dust!). From that point of view, an SF crank is a much easier proposition than and SFC due to the hardness of the latter. Man those webs are hard (especially the centres with incorporated crank pins!).
Christmas has come and gone and the last post I see on this topic is from last October, so surely there is some action to write about, real-world reviews, track tests? Would love to hear more about this and especially how the experimental balance factors turn out.
Thanks for reading.
Piranha Minore
Interesting read.About 20 years back I was at a mates place and he had a visitor.The visitor rode a Triumph Trident fitted to a Honda beam type frame.This blokes name was Mark Parker,brother of Fess Parker,musician from the OZ band The Radiators.Clever bloke this Mark.A couple of years later I read a test in a bike mag on a BSA twin also in a beam frame I think with a twisted crank made by a bloke called Mark Parker.A few years later I arrive at Tartha Pub on my 3C at the end of the first day of a Snowy Run and what pulls up at the pub for a minute or so but this same BSA with Mark on it.Sadly he leaves immediately so I missed a chat.Its a funny old world the OZ bike scene.
phil37
Hero member
- Location
- Lincolnshire
Steve's big bore SFC was converted to 180? - it went really well but did vibe a lot - we never re-balanced the crank - would have been interesting to see what it would have been like if we had of done. Steve rode my 90?SF and thought it was a bit too much work to try to sell to a customer - and Stuart Clark did a 90? conversion on a std SF motor for him - this ran Ok -but seemed really down on performance. He and Chris Palmer (the other half of Palmelli)did build a big bore 90?motor into a special monoshock frame - Steve was moving on from Laverdas at that point and had a few other problems -so i can't recall ever getting a lot of feedback on that one - it ended up with Chris and he later sold it on. - Regards - Phil
piranha-bro2
Hero member
- Location
- Melbourne
Hi Vince, that would be the fella I mentioned, no doubt whatsoever. Now I recall the name - and the town. Not sure how he managed to set up the suspenders on that Beezer - somewhat alters the weight characteristics of a superlight stroker twin RGV! Would have been good to ride that thing and see how well the balance part of his equation worked.Vince said:
Piranha
piranha-bro2
Hero member
- Location
- Melbourne
Hi Phil. Seems odd that converting to 270 would be much more work than to 180. I gather they put a hell of a lot of work into those frames/bikes, so getting a really sweet motor in there should have been priority 1.phil37 said:
Is you SF crank any lighter than a stocker? And are you still cradling it under a stock SF frame? I'm tempted to simply put my 270 SFC crank back together (pulled it apart after knocking noises scared me - turned out to be the Gates driven wheel loose on my Denso aternator conversion). I have some cases in excellent condition to mount it in, but should really pull the centres apart and machine up some balancing blanks to fit over the pin (as per Red's) for more accurate dynamic balancing - though I do have faith in static knife-edge blanacing if doen really well.
Cheers, Quentin
Cosi
Hero member
- Location
- Kingscliff
The article you read was in the fabled Streetbike mag, long since dissasembled after Seddo was neutered by ACP and then humbly went on to become the porn king
Mid 90's and well i was gonna get rid of my Lav and head to bega to get me one of these RGV Besas, it was called the "Spiteful 810" and used a 650 besa base bored and stroked out to 810, apparently it should blow its brains out, according to monsiuer Zane
A little search revealed the following, looks like old Micky is still at it and his latest incarnation looks a little bit tricker, looks not to disimiliar to one of those exploding thingies
http://www.britbike.com/forums/ubbthreads.php?ubb=showflat&Number=212693&page=all
Mid 90's and well i was gonna get rid of my Lav and head to bega to get me one of these RGV Besas, it was called the "Spiteful 810" and used a 650 besa base bored and stroked out to 810, apparently it should blow its brains out, according to monsiuer Zane
A little search revealed the following, looks like old Micky is still at it and his latest incarnation looks a little bit tricker, looks not to disimiliar to one of those exploding thingies
http://www.britbike.com/forums/ubbthreads.php?ubb=showflat&Number=212693&page=all
phil37
Hero member
- Location
- Lincolnshire
Hi Quentin - I meant that the amount of extra tuning work to get the higher performance would have been too costly as Steve was retailing these bikes at the time.
I made my crank from the two inner webs from a triple and had a 35mm centre pin made up - we had had a spate of the splined SF centres doing various conversions whilst we were riding them - not good! I used the triple webs as they have the crankpin integral with the web - and that erradicated any chance of the web splitting between the centre pin and the original crankpin boring. I then used std SF outer webs - turned down to same diameter as the inners (135mm I think). I thinned and lightened the outers and removed some of the metal near crankpins on the triple inners. I used carillo rods with the same big end dimensions as the triples and spaced the crankpin with a bronze thrust washer to get the correct centres. Had whole crank polished - it is very light - although I can't remember what it weighs. When I'd done all this - I saw my 1st SFC (later type) crank and realised that I'd done virtually the same as the factory - in fact my centre pin would be adirect replacement for the SFC original!
I had decided to gothe 90? route after reading the such well written "Not so Cranky cranks" article in a bike mag - this so fired me up - I just had to do it - if you want a copy - e-mail me and I'll send it to you. I balanced my crank as two seperate halves to 65% on a home made jig made from bedstead angle iron - so appreciate your steell rule idea! I had to add "Mallory Metal" to the crank as i'd over lightened it!
This bike runs so well - especially as I've now reduced the compression from over 11:1 to 10.2:1 - it's smooth and very rideable - regards - Phil
Paul,
10kgs is very optimistic.
IIrc, a '74-on SFC item weighs in at a tad under 12 kg, don'r remember if that's with or without outer mains.. My own efforts end at 12.2 kg, including outer main bearings.
Quentin,
Excellent food for thought, centering the balancing mass to counter the rocking couple! I'm in the process of machining a crank for my twisted project, will retain stock centre pin and rods though... not going racing with it. On the other hand, 2 of my lightened cranks with stock centres have got 2 whole seasons of racing on them without issues.
Here's some of my efforts;
piet
10kgs is very optimistic.
IIrc, a '74-on SFC item weighs in at a tad under 12 kg, don'r remember if that's with or without outer mains.. My own efforts end at 12.2 kg, including outer main bearings.
Quentin,
Excellent food for thought, centering the balancing mass to counter the rocking couple! I'm in the process of machining a crank for my twisted project, will retain stock centre pin and rods though... not going racing with it. On the other hand, 2 of my lightened cranks with stock centres have got 2 whole seasons of racing on them without issues.
Here's some of my efforts;
piet
