pf1
Hero member
- Location
- Portsmouth UK
It would take me all day to write a list of the things that broke on my 1971 Commando
Mikuni
- Thread starter Paul Marx
- Start date
rocketonarail
Hero member
- Location
- Gloucestershire,England
One thing about Amal Concentrics is that although they may wear relatively quickly , they are stone age simple ..... so easy to put right if needs be ,
therefore maybe better suited to the overall characteristics of the Laverda ....... and still available new , probably at quite a saving compared to Mikunis ....... ( Although I have`nt checked ) .......
I believe some SFC`s came factory fitted with Amals , so maybe fitment should be straight forward , unless there are any frame differences / clearance issues between SF and SFC .......... and if they are relatively cheap , you could always buy a spare set to fit when the first ones wear out ...........
I remember reading an article where Brettoni was comparing SFC`s fitted with Amals versus Dell `Orto`s ........ If I`ve got it right , he reckoned the more sophisiticated Dell`Orto`s gave better mid range response , whilst the Amal`s gave better results at full throttle ........
therefore maybe better suited to the overall characteristics of the Laverda ....... and still available new , probably at quite a saving compared to Mikunis ....... ( Although I have`nt checked ) .......
I believe some SFC`s came factory fitted with Amals , so maybe fitment should be straight forward , unless there are any frame differences / clearance issues between SF and SFC .......... and if they are relatively cheap , you could always buy a spare set to fit when the first ones wear out ...........
I remember reading an article where Brettoni was comparing SFC`s fitted with Amals versus Dell `Orto`s ........ If I`ve got it right , he reckoned the more sophisiticated Dell`Orto`s gave better mid range response , whilst the Amal`s gave better results at full throttle ........
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Good luck finding new 36mm Concentrics. Apparently these were made under license in Spain back in the day, new Concentrics these days are only available up to 32mm.
Concentrics may be dead simple, non-adjustable floats, the early ones didn't even have replaceable pilot jets, just a calibrated bore that had to suit all applications, just means they can only be adjusted "close" or "good enough". They'll never reap in any efficiency prizes. Material quality was about on par with pre-PHF/B Dellortos. PHF/B and VHB are in a next-higher league.
There shouldn't be any difference between Amals and Dells at WOT, much the same sort of hole with a needle half-way down, just comes down to jetting which works better. Imho, another myth, just like the PHFs emptying the float bowls via accelerator pumps, only simple maths required to de-bunk that one. The slightly superior fuelling of the Dellorto might offer better mid-range response, not exactly rocket surgery. After all, the Dellorto design is about 8 years newer than the Amals', wouldn't have been worth the effort if no progress were made.
Best bang-for-buck at the moment, if not searching for outright power, would be the humble Mikuni VM. Cheap, simple and does what it says on the box, for a very long time. But, as with all other carbs, an endangered species, won't be available for very long any more.
FWIW, I've run into huge problems setting up a '72 SFC with Amals. While the PHBs are a piece of piss and usually done in about 5 minutes, the Concentrics are proving themselves to be a royal pita. I'll get stuck into it again once weather and temps return to normal.
piet
The 36mm Amals were indeed Spanish made and used on some of their off road two stroke singles.
I seem to remember 200 pairs being commissioned by Moto Laverda. All were not used. Didn't Tim Isles buy a few spare?
Intake stubs are specific and not interchangeable withe the Dell'Orto ones.
Paul
rocketonarail
Hero member
- Location
- Gloucestershire,England
Yes ...... It was just a thought , mulling over possible carb choices .......
Tim Parkers book mentions Laverda ordered 200 pairs of 36mm Concentrics for the SFC , but not all were actually fitted ........
Pondering bore sizes ...... the 1000 / 1200 triples use PHF pumper 32 mm as standard ......... I believe the 750 twins used VHB 30`s , before changing to PHF pumper 36`s from 1973 onward ..........
If I had money to burn ( and a 750 twin of course ) , then I might be tempted to fit a pair of 32 mm Concentrics from Burlen just out of interest to see how they performed ....... ( I stuck a Concentric on a Tiger Cub once , in place of the Zenith .... seemed to work ok ... Also had them on Triumph 250 single / 750 twins and triples , and the Concentrics were one of the few things that actually seemed to work properly ..... ) ........
But if inlet stub spacing and so on is going to be a problem , then it sounds like it`s going to be more trouble than it`s worth .......... and then there`s all that messy tickling ...........
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I would need to try an Amal on a stock inlet.
Paul
breganzane
Hero member
- Location
- NSW Australia
I have the Amals on my SFC. I don't know how much the carbs contribute to the overall vibe of the bike but it is hilariously obnoxious and ill mannered. But it starts easily with a tickle and runs cleanly throughout with a great top end. It even idles fine. On or off the power is good but I guess the only thing is light constant throttle riding is a bit... err... 'unrefined'. With the 2-2 peashooter meggas, holding a constant throttle in a low gear with some revs on sets the machine into a riotous warbling cacophony that brings joy to a small proportion of (mostly old) people and presumably annoys the hell out of everyone else. Not my fault, they're all like that mate. 
I do recall Marnix being surprised it ran quite well with the Amals, most having given up on them years hence and fitted Dellortos. When Chris Cutler was racing it on Methanol he fitted Dellortos for that.
Anyhow, given the scarcity, the 36mm Amals are unlikely to be a good option for someone else's 750 anyway, but perhaps the smaller ones would be an interesting experiment particularly on a small valve motor? Certainly going to result in old-school uncivilised behaviour but sometimes that's fun. The most enjoyable Lav 750 I've ridden on the street is still probably the heavy crank small valve first series SF with the 30mm square slide Dells (more like a 750S with the first Laverda brakes).
I do recall Marnix being surprised it ran quite well with the Amals, most having given up on them years hence and fitted Dellortos. When Chris Cutler was racing it on Methanol he fitted Dellortos for that.
Anyhow, given the scarcity, the 36mm Amals are unlikely to be a good option for someone else's 750 anyway, but perhaps the smaller ones would be an interesting experiment particularly on a small valve motor? Certainly going to result in old-school uncivilised behaviour but sometimes that's fun. The most enjoyable Lav 750 I've ridden on the street is still probably the heavy crank small valve first series SF with the 30mm square slide Dells (more like a 750S with the first Laverda brakes).
chrisk
Hero member
- Location
- Brisbane, Australia
I’ve been told of the pros of fitting Lectron carbs to twins, apparently easy to set up.
Anyone here tried them?
Anyone here tried them?
There still being made in the USA Chris and Queesland have a distributor. A mate had one on a KTM Dirtbike years ago, it went ok but was pretty flat on the pipe. It was a 2 stroke. They make all kinds for all kinds of bikes.
Tippie
Hero member
- Location
- Dr?bak, Norway
I had a pair of Ei (same as Lectron) on appro back then. Were dead easy to set up for idle, and WOT on the dyno (had a smidge more hp over dells) and for general riding, but they were way lean in midrange which is where that profiled special needle is the thing. Other than that they felt great. Maybe I should have tried a stack of different needles but I handed them back.
chrisk
Hero member
- Location
- Brisbane, Australia
I have a pair of Lectrons on the shelf that came with a SF1 in boxes
Rokka
Junior member
- Location
- Peterborough
Ok, Well that makes more sense...
Personally i think different horses for different courses.
I have a couple of BSA B50 MX's that still run points! tried Boyers, (best in the bin!)
Least with points on a big ish single the Plug fires how ever slow the engine spins.. well that's the way i look at it.
Ran my T120 RV with points for about 35 years, till a points foot randomly broke so swapped to TRISPARK.
My old T120 beach race bike is still on Magneto! which is always fun in the Paddock.... if not my bike... then others! as people think you know stuff.
other than that its a Black box for me too
You unlucky, me lucky. Had Boyer Bransdon on my B44 Victor for over 40 years, never failed to start, never needed attention, runs at all revs in all conditions pulls brilliantly, Experiences vary obviously but undoubtedly the best mod I ever made to that bike.
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CDHE
Full member
- Location
- Boulder, Co
I have pulled the trigger with Tophams on a set of Mikuni TM36-B150 carbs with a second (right) fuel intake for my SF2. Price was reasonable, and promised turnaround quite quick. I wonder if anyone might be able to help with pics/ideas for eliminating the stock air filter/battery tray combo in favor of a simplified battery perch.
Let us know how it goes.
Paul
I removed my Boyers and gave up with them after timing and strobing my Short Five CCM B50 one day and finding that it didn't correspond to the static marks.. !
next day wouldn't start... retimed it.... now the static marks worked ... what the.
Later found out that Simon Cheney ... Eric's son... (Eric Cheney of BSA frame fame) had had the same issue..
I can only guess that perhaps pulses from the charging circuit was interfering with the signal from pickup.
Tippie
Hero member
- Location
- Dr?bak, Norway
Have a look at that SF2 for sale in New Mexico in the for sale section here on the forum. It is easy to keep the original battery tray and just fabricate something to replace the original airbox if you want to.
I have kept the front of the original airbox and removed most of the back of it, kept the original rubbers to the carbs with foam filters stuffed up into them from the inside of the airbox, been like that for several decades. I like having all that stuff closed in between the side covers.
If VR ( Variable Reluctor ) pickups, they are a trade off in impulse cam velocity to VR pole face characteristics, most prominent being the TEAG or total effective air gap. They are not an exact scientific instrument, its a pickup relying on magnetic gap transfer, not well understood in basic mechanical worlds. HTH j. ** 0,025m/m is a commence gap, in operational installation.
CDHE
Full member
- Location
- Boulder, Co
you do not need the heat isolaters now you will be using a rubber coupling so remove them
saves you some room