1034cc SF Engine build (Slowly)
- Thread starter julian
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Laverdalothar
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- Germany
Hi Julian,
a) the top is hidden by the tank - what's the problem? Or are you riding without a tank??
b) if you look into the FCR and into the PHF/PHM from the inlet side while slider is wide open, you will directly see why the Flatslides do work so superior.
Basically, the Airflow should be the highest at the point of vaporization (e.g.: at the needle). With the Dell'Ortos, that is the point with the least airspeed. Simply because the slider is bigger than the inlet or outlet, so, on a 32mm PHF f.e., the Slider is 38mm. That means, the "channel" if you will opens up at the point where the highest speed is needed to suck the fuel from the needle/Needlejet. Flatslides have simply one size at all points, almost like a tube. The CR do suffer a bit from that, too, but not as much as the PHF/PHM
The FCR btw. do have an acceleration pump, just like the Dell'Ortos.
Ride a bike with RS36 or FCR39 and ride one with Dell'Ortos, no matter what size. You will recognize the difference right away. On my Jota I have had 32, 36 and 40mm Dell'Ortos as well as 41mm FCR. The difference is so significant, you would not believe it. Why do you think do many Ducati Monster owners change the OEM carbs to Keihins?
If you like some more info: http://laverdaforum.com/forum/index.php/topic,41318.msg61374.html#msg61374
a) the top is hidden by the tank - what's the problem? Or are you riding without a tank??
b) if you look into the FCR and into the PHF/PHM from the inlet side while slider is wide open, you will directly see why the Flatslides do work so superior.
Basically, the Airflow should be the highest at the point of vaporization (e.g.: at the needle). With the Dell'Ortos, that is the point with the least airspeed. Simply because the slider is bigger than the inlet or outlet, so, on a 32mm PHF f.e., the Slider is 38mm. That means, the "channel" if you will opens up at the point where the highest speed is needed to suck the fuel from the needle/Needlejet. Flatslides have simply one size at all points, almost like a tube. The CR do suffer a bit from that, too, but not as much as the PHF/PHM
The FCR btw. do have an acceleration pump, just like the Dell'Ortos.
Ride a bike with RS36 or FCR39 and ride one with Dell'Ortos, no matter what size. You will recognize the difference right away. On my Jota I have had 32, 36 and 40mm Dell'Ortos as well as 41mm FCR. The difference is so significant, you would not believe it. Why do you think do many Ducati Monster owners change the OEM carbs to Keihins?
If you like some more info: http://laverdaforum.com/forum/index.php/topic,41318.msg61374.html#msg61374
Julian,
It's basically the smooth-bore design of the current Micky or Keihin carbs that offers the biggest advantage over a conventional carb, they simply flow far better. Doesn't matter that much if flat- or round-slide either, don't know of any currently available smooth-bore round-slide carb larger than 35mm though (Amal MkII perhaps?). You could even fit TT/GP Amals or Dellorto SSIs, great traditional carbs, but they do have a price......
Flatslides do have one major shortcoming though, they rattle like a pack of Smarties at idle!
piet
It's basically the smooth-bore design of the current Micky or Keihin carbs that offers the biggest advantage over a conventional carb, they simply flow far better. Doesn't matter that much if flat- or round-slide either, don't know of any currently available smooth-bore round-slide carb larger than 35mm though (Amal MkII perhaps?). You could even fit TT/GP Amals or Dellorto SSIs, great traditional carbs, but they do have a price......
Flatslides do have one major shortcoming though, they rattle like a pack of Smarties at idle!
piet
Laverdalothar
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- Location
- Germany
sfcpiet said:
That's true. Have thought about how to solve that but did not come to a good solution yet. On the Keihins, there is a plate in front of the slider that might cause that rattling sound. If that is the case, a bit of glue could cure it. But I fear it is the hole slider that causes it, which is not that easy to fix as you can't take away the free-play between the rollers of the slider and the housing, as then the rollers would not move anymore. TDM's would be better then, as they have a different guiding of the slider. But they do cost way more than the FCR, too...
Romeo.D
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- Zadar - Croatia
sfcpiet said:Julian,
It's basically the smooth-bore design of the current Micky or Keihin carbs that offers the biggest advantage over a conventional carb, they simply flow far better. Doesn't matter that much if flat- or round-slide either, don't know of any currently available smooth-bore round-slide carb larger than 35mm though (Amal MkII perhaps?). You could even fit TT/GP Amals or Dellorto SSIs, great traditional carbs, but they do have a price......
Flatslides do have one major shortcoming though, they rattle like a pack of Smarties at idle!
piet
That ratlle is music for ears , ad dry clutch ratlle to it and asocial exhost and you have perfect motorcycle sound .
Laverdalothar
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- Germany
Hi Romeo,
well - that is obviously (again) a question of personal taste. I f.e. don't like the Ducatis rattling, but I don't care to much about the sliders rattling in my bikes, as it only happens in idle, and I don't keep them in that rev-range for to long...
well - that is obviously (again) a question of personal taste. I f.e. don't like the Ducatis rattling, but I don't care to much about the sliders rattling in my bikes, as it only happens in idle, and I don't keep them in that rev-range for to long...
Romeo.D
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- Location
- Zadar - Croatia
Laverdalothar said:Hi Romeo,
well - that is obviously (again) a question of personal taste. I f.e. don't like the Ducatis rattling, but I don't care to much about the sliders rattling in my bikes, as it only happens in idle, and I don't keep them in that rev-range for to long...
As ex radio officer i am used to all cineds of "strange" sounds wich make sense in my ears. Like the sound of cam sprocket drive by Honda rc 30 , 10 years i have Honda NS400R with Joly Moto exhost , FCR idle sound on ZXr750R this is music for my ears etc. .
sfcpiet said:Julian,
It's basically the smooth-bore design of the current Micky or Keihin carbs that offers the biggest advantage over a conventional carb, they simply flow far better. Doesn't matter that much if flat- or round-slide either, don't know of any currently available smooth-bore round-slide carb larger than 35mm though (Amal MkII perhaps?). You could even fit TT/GP Amals or Dellorto SSIs, great traditional carbs, but they do have a price......
Flatslides do have one major shortcoming though, they rattle like a pack of Smarties at idle!
piet
Thats so true Piet, , except for a 200 rpm window somewhere around 2k
Laverdalothar
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- Location
- Germany
idle at 2K??? You shouldn't have taken THAT much counterweight off your crank, Rob...
Romeo.D said:
And I, as an engineer, are very suspect of anything mechanical that's noisy! Imho, mechanicals should operate smoothly and silently, old stationary petrol or steam engines are a fine example, all that is audible is the puff-puff of the exhaust.....
So it should be with a motorcycle engine, a smooth and harmonic togetherness of individual components. No rattling, no clanging around, a faint ticking of tappets and whirring of chains is about all that's acceptable, and if the exhaust note is subdued (fat chance within the Lav scene...), fantastic! 8)
As soon as mechanicals start rattling/knocking/rumbling, they're either fucked or badly designed!
piet
L
lemonjelly
Guest
Yamaha FS1E comes to mind
L
lemonjelly
Guest
oooh Kenwoods mm,Actually a Fizee on tick over was the smoothest and quietist moped around at the time.I had a three gear Puke but thread digression eh Dave
Simonr501
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- Lympne, Kent. UK
Puch.
laverdakeith
Hero member
pooch ?
Laverdalothar
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- Germany
GregT
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- Location
- Christchurch NZ
Piet, I suppose it would be possible to insert anti - rattle springs into FCR's....but I'm used to getting someone to put their fingers on the slides while I try and trace the other noises.....
Julian, if you really want the period look....what about a bronze bodied 48DCOE ? Sure it's about 4 Kg, but very "period"..
You won't be using "plain" Dellortos anyway, if you want the response that you would get with FCR's you'll be using Dellortos with accelerator pumps...which are just as cluttered around the tops as FCR's IMO.
If you really don't like the modern CR tops with the cable reel, convert the tops to direct cable lift...not too hard.
And yes, I reckon for your big motor CR's around 39mm or PHF40's would be about right.
Julian, if you really want the period look....what about a bronze bodied 48DCOE ? Sure it's about 4 Kg, but very "period"..
You won't be using "plain" Dellortos anyway, if you want the response that you would get with FCR's you'll be using Dellortos with accelerator pumps...which are just as cluttered around the tops as FCR's IMO.
If you really don't like the modern CR tops with the cable reel, convert the tops to direct cable lift...not too hard.
And yes, I reckon for your big motor CR's around 39mm or PHF40's would be about right.