Dellortoman
Hero member
- Location
- Tasmania, Australia
PHF36 Carbs aren't from a triple. They all came with PHF32 from the factory.
Carb Question
- Thread starter oehlin
- Start date
OK, But my throttle slide 60/2 is wrong according to Laverda Paradise catalog and should bee 50/3. Do You think the differens matter ?
Cutaway affects carb performance from 1/8 to 1/2 throttle. The bigger the number the higher the cutaway is, allowing more air in the mix. The other number is the height of the slide where the accelerator pump squirts a stream of raw fuel directly down the inlet tract if it's working, lots don't. Easy to see this stream by looking down the inlet
Yes
CLEMTOG
Hero member
plenty of triples have had 36mm PHFcarbs fitted, and the jetting is very, very close to when 32mm PHF's are there, which is stock, a lot of people have retro fitted the 32's making the 36's available, there is no gain without other engine tuning and proper setting up, eg dyno and clued up operator. Fit some 36's and guess the jetting and you will gain only higher fuel consumption, most heads do not benefit much from 36mm carbs anyway, the casting does not allow much in the way of port changing, only polishing realy 32's are great, the porting on the Corsa and SFC1000, with their very much bigger valve sizes, do give a better state of flow and this can be optimised with a properly designed exhasut, not Jota cans which were in fact stock silencers opened, de-gutted and bolted on, no design whatsoever, I was there, for one of those dyno runs at Slaters Collington, the cans were just cut up, cut and shut, capped off and re-welded.
CLEM
CLEM
Tippie
Hero member
- Location
- Dr?bak, Norway
Those pilot jets are huge. I run 45 (pretty sure I have already told you that), many people prefer slightly richer 50. How many turns out is your mixture screw? With those pilot jets it is likely to be way rich under normal riding and cause it to stutter as if the choke is partially on (and you have checked that the choke plungers are properly seated and their rubber insert seats are in good shape?). If you fit 50 slides with those 60 pilot jets it will be even richer. The needle will be a K2, and the needle jet a 265 unless someone has mucked around with it. The slide cutaway actually has it's major effect in picking up from closed throttle, but as Vince says they affect slightly more open as well. I had 70 slides fitted once as they were all I could get. The bike could idle perfectly but to get it to pick up from idle I had to richen up the idle mixture heaps. You should be able to get it to run properly with those huge pilot jets and 60 slides though. For myself I would fit 50 slides and 45 or 50 pilot jets. It should then idle fine with the usual 1 1/2 to 2 turns out mixture screws unless there is some other problem. Almost all riding is with very small throttle openings so this is the area that is most noticeable. How are you synchronising the carbs?
piranha-bro2
Hero member
- Location
- Melbourne
Also ran 70 slides in my SF and had no tuning issues whatsoever. Would have preferred 60s but weren't available at the time.
Do as Tippie recommends and you will have it running sweetly.
Do as Tippie recommends and you will have it running sweetly.
The carburetors are synchronized using two 2mm drills under the throttle slide and they lift evenly
Tried with the pilotjet 50 and then the engine did not want to start.
Then I tried the pilot jet 55 and the engine tried but did not start.
With the pilotjet 60 and 2 turns on mixture screw, the engine started but stalled below 2000rpm.
Have ordered the pilot jet 65 + 70 to see the effect of these.
Chock plungers are new.
Wishing all of you a Happy Easter.
Tried with the pilotjet 50 and then the engine did not want to start.
Then I tried the pilot jet 55 and the engine tried but did not start.
With the pilotjet 60 and 2 turns on mixture screw, the engine started but stalled below 2000rpm.
Have ordered the pilot jet 65 + 70 to see the effect of these.
Chock plungers are new.
Wishing all of you a Happy Easter.
CLEMTOG
Hero member
using drills to get a "base starting point" is good, but oinly for a starting point, sychronising with a quality instrument (s) will give you a very satisfying result, 750 twins have a habit of showing when synchronising is needed, by ticking over at red lights for instance, for maybe two minutes then dying, choke is needed to get going again, and THAT IS clear signage that your carbs are out, they should tockover indefinately. Be warned though that on ticklover oil circulation is marginal, so even though this proves good carb set up, if you were get stuck for more than a few minutes, kill the motor.
CLEM
CLEM
My first goal is to make it tickover
I don't know what's up with your bike.My first goal is to make it tickover
Synchro will not affect idle unless it's wildly out. And it should more or less run on one cylinder anyway.
My SF2 runs fine on standard carb settings, 55 pilots, 140 mains, K2 needles, 50 slides. If anything, it's a bit rich.
As for synchro, I just stick a finger in the carb intake and make sure that they top out at the same time. Probably not a good technique but it's been going 30 years.
Paul
I agriee Paul. The synchro is not the problem. Must bee something else that causes my problem
What needles have you got in there?
Have you got the right mixture screws, there are 2 different lengths?
Have you got the right slides, or modified a new set to correspond with the old carbs if that's what you've got? ( Though new model slides in old carb bodies will probably send the revs way up)
Paul
How do I recon right needles. and if I got the wrong ones should they affect tickover ? 2000rpm and up seems OK
Mixture screws block the passages when fully screwed in so I suppose they are the right length.
Slides 60/2 seems old butt not worn or modified
Wrong needles will affect low down running. Needles should be marked K2, and the clip in the middle notch. It needs good eyes to see the marking and of course dismantling the needle.
Paul
piranha-bro2
Hero member
- Location
- Melbourne
65 or 70 pilots are totally wrong. You need to to look elsewhere for the solution = find the fault. I would be VERY surprised if a needle had any effect on lifting off idle.
Using full throttle as a guide to carb sync is problematic because the most sensitive part of the throttle lift is at and immediately off idle. Much better off getting a very smooth and balanced idle, then feeling/listening for slides to rise or drop from/to the idle speed adjusting screws.
Using full throttle as the guide might mean one slide rises 1mm before the other even leaves its idle stop, which means cruising at anything under about 100kph you're almost on one cylinder.
Using full throttle as a guide to carb sync is problematic because the most sensitive part of the throttle lift is at and immediately off idle. Much better off getting a very smooth and balanced idle, then feeling/listening for slides to rise or drop from/to the idle speed adjusting screws.
Using full throttle as the guide might mean one slide rises 1mm before the other even leaves its idle stop, which means cruising at anything under about 100kph you're almost on one cylinder.
Davo
Senior member
- Location
- West of the Rabbit Proof Fence
From new ex factory?
Tippie
Hero member
- Location
- Dr?bak, Norway
I would certainly take Paul's hint and make damn sure that the mixture screws are the correct ones, with their o-rings. Surely someone here can give a pic of them. I know from Guzzi owners that they have had headaches from this issue. Also the slides as the replacements are no longer a direct replacement.
Needles do not affect idle at all. I rode my bike with a broken off needle 1000km once, on a tour the slides/carb bodies were so worn that the needle snapped off and sat in the needle jet. I tried riding without it at high speed (outback Australia) but that side wouldn't cut in, so I used the choke to supply fuel to that side, doing multiple plug chops to check mixture, and at a steady 110kmh it was the right colour so I got myself to the nearest Ducati shop and bought new carb stuff. The bike idled perfectly with the needle sitting in there but wouldn't pick up enough to be rideable.
The other issue is that I have more than once had an SF come in for service with massive pilot jets and still lean as fuck, and run really weak at lower revs, and need to get over 4000 or so to start to develop any power, having been like that for years and the owners actually having bought the bikes like that. These bikes had the cam timing one tooth out and when It was rectified they went back to more normal jet sizes and ran great.
As for synchronising, I am firmly with PB2, it is pick-up from closed throttle on any bike with slide stops where it manifests itself most. If the vacuum is a scrap different at half or full throttle there are other issues.
Needles do not affect idle at all. I rode my bike with a broken off needle 1000km once, on a tour the slides/carb bodies were so worn that the needle snapped off and sat in the needle jet. I tried riding without it at high speed (outback Australia) but that side wouldn't cut in, so I used the choke to supply fuel to that side, doing multiple plug chops to check mixture, and at a steady 110kmh it was the right colour so I got myself to the nearest Ducati shop and bought new carb stuff. The bike idled perfectly with the needle sitting in there but wouldn't pick up enough to be rideable.
The other issue is that I have more than once had an SF come in for service with massive pilot jets and still lean as fuck, and run really weak at lower revs, and need to get over 4000 or so to start to develop any power, having been like that for years and the owners actually having bought the bikes like that. These bikes had the cam timing one tooth out and when It was rectified they went back to more normal jet sizes and ran great.
As for synchronising, I am firmly with PB2, it is pick-up from closed throttle on any bike with slide stops where it manifests itself most. If the vacuum is a scrap different at half or full throttle there are other issues.