My base settings for 36mm PHF Dellortos SD Darmah

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ALinHB
Cucciolo - the Lil Pup
Posts: 14
Joined: Thu Aug 20, 2009 3:00 pm
Location: Hawks Bay Napier New Zealand

My base settings for 36mm PHF Dellortos SD Darmah

Post by ALinHB » Sat Oct 17, 2009 7:41 pm

For those of you that need a starting point for 36mm PHF dellorto carbs from 32mm carbs.
This is what i done for set up and fit up for riding here in NZ.

Just to mention that the bike is a 1981 SD Darmah.
I orginally had 32mm PHF.

To fit the 36mm carbs clear of all rubbing and for tuning access i cut back the original manifolds just back far enough to remove the standard o ring groove. This allowed my rear carb to completely clear the side cover and cables have good natural flow to them. Also the fuel pump cover at top of carby dose not hit the seat base. I have a 90 degree air filter rubber that fits in real nice. I cut back both manifolds so they are the same. Fitted new manifold rubbers, S/S nylock nuts and washers. Do not over tighten them. I removed the straight cable adjusting screws from 32 and fitted them to the 36mm's. New cables right back to the grip and good time to oil them is now. After set up I could not for the life of me get it run as they come. Hence my plea's for help at this site. But had no responce as maybe i am the only one on th planet that's done it.
Argue, jump up and down, scream your head off at me but this is what is running sweet for me and my old girl.

Jetting and setting:
Slide 60/3
K18 needle (clip on 2nd bottom slot)
65 Idler jet
130 Main Jet
atomiser AB265
Air mixture screw 1 and a quater turns out

Get on it and ride.


New Carbs jetting at purchase:
Slide 60/3
K18 Needle
50 Idler
130 main
Atomiser AR 268

For those of you that remember my problem about crackling and backfiring at throttle back off after i got the duke running from basket case (32mm at the time). I covered a lot ground then on idea's from you all. I originally listed a question about cyclinder pressure testing range (tested perfect). We found jets on top of jets, (thanks for your info on that one Steve), exhaust air leak- blocking pipes off and shoving the air hose up it and spraying soapy water (round up with a new set of conti's to make sure problem fixed), manifolds leaking, timing issues, pick rewiring (done by the way), pick up ohm's testing spot on at 220 and list goes on and on. Thanks to you all. Good bunch of guys out there to draw a reliable source of info from. I appreacited the help offered. My knowledge of SD Darmah's now is paramount. After saying that, i reckon my initial problem stemed from carby jetting all along. So what happened to the PHF 32mm carbs? I am a keen range shooter. Do i need to say any more.
They suffered terribly out there on that fateful day. One round from my 30-06 when straight threw the air intake blasted the slide to pieces and exited out the other side. Bull's eye. My mates anti tank rifle put the second carb to rest. (It was the rear carb i think) Still can not find all the pieces. This was the only way i could make sure they were safe from contamiting anybody else out there.
Cheers
Al

Elliot
Cucciolo - the Lil Pup
Posts: 20
Joined: Tue Apr 18, 2006 10:19 am
Location: Christchurch, New Zealand

Good news Al

Post by Elliot » Sun Oct 18, 2009 2:22 am

I also own a 78 Darmah with 36mm D's on it. I replaced the 32mm as they were worn. I am having trouble with the engine running on one cylinder (front from memory) and have undertaken the vast majority of what you recommended. I will check my jetting against yours and report back. But from memory I left the carbs as they were when they arrived.

I have a 2 into1 fitted which looks like an Alchemy set up. I bought it from a guy in Melbourne about 12-13 years ago. It never came with a clamp from the headers to the muffler and I wonder if that has caused me some trouble with exhaust leaks and backpressure.

Did you do the work yourself?
Owner of two 78 Dramahs as I can't afford a 900SS or a Greenframe!

ALinHB
Cucciolo - the Lil Pup
Posts: 14
Joined: Thu Aug 20, 2009 3:00 pm
Location: Hawks Bay Napier New Zealand

Post by ALinHB » Sun Oct 18, 2009 12:55 pm

Hi Elliott
It would be good for you to check what settings you have and let me know so i can compare.
Yes i done the work myself. All very simple stuff. Pick up wires were a challenge as i am not to fluent on wiring. But there is a good drawing from steve posted on one of the topics that i followed and worked fine.
The problem i had was after cutting them back, i could not remember which was which cause the coating disintergated on touch. Bugger.
I purchased some of that new high tech wire that steve sells and colors match, so it is easy. The only problem after that was getting the rubber on the case to tightn up enough to seal. I managed to source a large rubber and Bob's your Uncle.
Maniflod cut back is straight forward. Crab a hacksaw and cut throught the rubber O ring groove. Then hand file back to square. I suppose it is easy saying that if your a steel fabricator like me. But don't worry. Just do it if you need to. Plenty of manifolds out there to refit your 32mm back on if needed. The PHF 36mm carbs come with rubber slip on and clamps. The standard manifolds were just about 4-5mm too long. Caused my rear carby set up to be up against the side cover. Another little trick i used you can do is slightly tap the side cover rubber mounting bracket out a little. Just gives a bit more clearance. I could not even get my bike to run on the 36mm carbs when bolted straight on. Had to have the choke on for it even to fire up, spitting, coughing backfiring. What a mess.

Regards to your front cyclinder problem.
Just from what I have exprienced, if you have checked out the obvious like spark plugs, plug leads, coil and ohm reading on pick ups etc. Check that the pick up wires are firmly in the connection. This is what i had once. Pulled the connection plug apart and reconnected it. From that moment on the bike would run but only really on one cyclinder. I would feel the cyclinder's and one would be warm and other cold. I removed the plugs and turned motor over to fine both plugs sparking. Back one was a harder spark and brighter than the other cyclinder. Problem turned out to be when i reconnected the electrical 4 into 4 pick up connection from pickups to transducers that one wire had not pushed fully back into connection. I removed the connection completely and fitted the separate bullet connectors.
Get some clamps on those pipes Elliot. Air sucking in, can and will, cause crackling back threw the exhaust at back off. I smear exhaust paste as well on my joins. Don't over tighten clamps as this puts pipes out of round and can cause sealing problems.
I would like to know what your jets are. Even though my Duke is running quite good now, it is good to compare. To check your ohm reading is also dead easy. Disconnect your pick up wires where they conect to your transducer wires. Insert each meter probe of the ohm meter into pickup wires and switch on. Will give you reading. Bike dose not need to be running or turned on as your ohm meter provides its own power to meassure. My reading were 220 and 224. With in the + or - 5% range. This checks your pick up rewiring is successfull.
Cheers
Al

Lumpy
SD900 Darmah
Posts: 322
Joined: Sun Mar 25, 2007 5:49 am

Manifolds

Post by Lumpy » Mon Oct 19, 2009 2:59 pm

Is there a difference between manifolds used on a 32 or a 36 or a 40mm carb?? What I mean is can differnt carbs be bolted onto one manifold and still acheive air flow and power gains?? Or does a 40mm carb need a 40mm manifold so no step happens at the intersection??

ALinHB
Cucciolo - the Lil Pup
Posts: 14
Joined: Thu Aug 20, 2009 3:00 pm
Location: Hawks Bay Napier New Zealand

Post by ALinHB » Tue Oct 20, 2009 10:52 am

Hi Lumpy

I am no expert on motor rebuilding. I only know what i have learnt in the 70's when i was stuffing around drag racing. The theory in those days were for instance, if you were to put a 40mm carb on a bike that took a 32mm for instance, one would port out the intake manifolds or heads and also installed larger valves to suit as well. Roughly port the intake area, not smooth. Leave rough to help turbulence of mixture. Unless running on eythonol. The exhaust port also got the treatment, larger valves and port out the exhaust ports making sure the ports on exhaust are smooth as to allow no turbulence or restriction. Also beef up the compression and alter your cams to suit your bike riding. But i think that when using your bike as a street machine or cuirser, don't worry about any changes. Just bolt them on. I myself would not go straight from 32mm to 40mm on a bike unless i was going to configure it for racing. Too bigger jump. Probly wind up tuning them down anyway and get no real benifit except using more fuel.
I went to 36mm from 32mm dellortos because my carbs were those emission control model that had jets on top of jets. They made them for 1 year. I am not into pollution control so that is why i gave them the treatment at the rifle range. Also they were 30years old and flogged out. Steve had 36mm dellortos on special "new".

How are you going with those setting on the 36mm carbs Elliott. Can you post a report on them. Keen to know what your's are. Steve dropped me an email and said mine should have been ready to bolt straight on out of the box. Maybe climate and engine configuration gave me some greif. Hard to say. My Duke runs good now anyway.

Cheers Al

Lumpy
SD900 Darmah
Posts: 322
Joined: Sun Mar 25, 2007 5:49 am

intake manifolds

Post by Lumpy » Tue Oct 20, 2009 1:14 pm

Intresting stuff about the turbulence. Some time back i saw a product (can`t remember for the life of me where) that was basically shaped like a fan but was intended to be stationary in the intake of the carb. The idea being that as the air rushed in through this device it would take on a twisting like motion causing the air to spin going down into the cylinder. The idea being to cause turbulence and there for cause a more even mixure with the air and then more complete combustion.
Another article I read about porting intake tracts was that the only real way to gain horsepower here was to be done on a flow bench. The article went on to say that in some cases material was actually added to the port in an effort to get the correct flow/turbulence required.
If your interested in that sort of stuff a great reference book is Tuning for speed by Phil Irving. Mr Irving was quite legendary in this department and I beleive is credited with having designed the Vincent black shadow/rapide V twins amoung other things. The book is well written and easy to follow and although aimed at engines that are now deemed as elderly many of his methods and equasions are still valid today.

Elliot
Cucciolo - the Lil Pup
Posts: 20
Joined: Tue Apr 18, 2006 10:19 am
Location: Christchurch, New Zealand

36mm Carb Jets

Post by Elliot » Tue Oct 20, 2009 6:53 pm

Al
Here are my jet sizes. Apologise for the delay. Uni has been busy.

Here are the jet sizes from my 36mm carbs. This is the jetting for the front carb.

K4 needle in the middle groove, a 7450 8gram float, AB265 needle valve jet, 60/3 slide, 138 main Jet, 65 idle jet, 35 atomiser jet, 75 starting jet and a 250 float valve jet.

For the rear carb it has a 140 main but I cannot remember why they were different. From memory it was something to do with the rear cylinder running hotter thus burning a slightly richer mixture would make it colder. I am probably about to be rained on by some irate bevelheads for having that description the wrong way round.

To be fair for road use it probably does not make much difference between the 138 to 140 jet.

Elliot
Owner of two 78 Dramahs as I can't afford a 900SS or a Greenframe!

ALinHB
Cucciolo - the Lil Pup
Posts: 14
Joined: Thu Aug 20, 2009 3:00 pm
Location: Hawks Bay Napier New Zealand

Post by ALinHB » Wed Oct 21, 2009 1:01 am

Thanks heaps Elliot

Very little difference between our settings. Only real point of notice is the needle. K4. I am off to check it out. By the way if you need a good web site to go to, try this one.

http://www.ducatimeccanica.com/default.html

Skroll down the web page untill you get to carburation and look under needles.
Excellant comparsions here. Looks like you may have a slightly richer needle if i am right. Bit hard to read what B is on the chart being as blind as a bat that i am getting these days.
It is not too unusal to run a different jet on each cyclinder like you got. I always do main jet reading the old school method. Go out on the highway and open the throttle so your sitting on about 4000 revs in top for a few kilometers. Then pull your clutch in, pull over, shut it off. Pull plug out and look at it's colour for a reading. Adjust main jet to suit. Cheers, thanks again.

Hi Lumpy

Interesting stuff you wrote about. The fan idea sounds like a turbo boost as well as turbulence. More atomising and fuel mixing, the better the combustion alright. Better burn in the cyclinder.
The theory behind polishing smooth the exhaust ports was to get rid of the burnt gases ASAP after it leaves the cyclinder. To extract the exhaust gases almost like a vacumn. The best exhaust systems are designed around air flow at predetermined speed creating a vacumn at the end of the pipe. Sounds like bullsh*t I know. More air in, means more out. I gave up building hot motors 30 years ago. Best to build reliable ones now.
Cheers Al

Ray O'Donohue
Parallel Twin
Posts: 119
Joined: Tue Oct 13, 2009 8:11 am

Dellorto slides re accellerator pumps

Post by Ray O'Donohue » Thu Oct 29, 2009 12:50 pm

I strongly suggest 60/1 rather than /2,/3 etc. for any and all Dellorto applications and sizes,with 5cc per 20 squirts as the volume adjustment. The /1 slide gives instantaneous activation of the pump when you first open the throttle,which is surely the only time you want or need it. The other alternative is to disable the pumps altogether.This was Gospel in the old days.

Lumpy
SD900 Darmah
Posts: 322
Joined: Sun Mar 25, 2007 5:49 am

slide ramps

Post by Lumpy » Fri Oct 30, 2009 8:06 am

Interesting stuff there Ray. I run /1`s in my bikes but have a set of /2`s laying around. I did try them once in the GTS but she ran like a pig but I`m tipping it was more to do with the cut-away than the ramp. My understanding is that the cutaway effects your progresive throttle opening. But it`s something that crosses my mind from time to time. I kinda thought that I love that down low grunt they have and wanted to enhance that. But then some thing always rings in my head that they have that torque there already so maybe it`s the midrange that I should enhance with the accelerator pump hitting it further up the rev range. As I don`t have a full compliment of slides with different ramp/cut-away combinations I can only dream on.
It would be interesting to hear from anyone else on the positioning of the ramps. Both my bikes came with /1`s as standard, the spare set of /2`s I have came from a new set of carbs I bought ages ago.
Perhaps the later acting ramps are aimed at racing applications where higher rev ranges are required.
As for the accelerator pumps, if I drain my float bowls or dismantle my carbs on the SS (40mm) when I put it back together and turn the juice on the pump at the back pot does`nt work. I spent considerable amount of time trying to prime it to no avail. As I was late for an appointment I took off with it not pumpng. When I arrived at my destination and checked it was working fine. Now if I drain or dismantle I put it back together ride 10minutes down the road and it`s working fine. Point being for that period that it`s not pumping I can`t notice any difference at all. It still seems responsive and eager to get down and boogie as always. But I guess the exact moment it starts working is unclear. Perhaps the manifold vacuum or vibration gets her pumping during the warm up period and it`s already working by the time I apply a twist of the wrist.
I`ve had quite a few big bore dirt bikes none of which run pumper carbs and they seem to go plenty hard.

Ray O'Donohue
Parallel Twin
Posts: 119
Joined: Tue Oct 13, 2009 8:11 am

Post by Ray O'Donohue » Fri Oct 30, 2009 8:28 am

The switch to /1 pump timing came to the Ducati world via a guy named C.R. Axtell,a noted XR750 Harley tuner of the 1970's,and it made EVERYBODY'S bike run a whole lot better.Why any other pump timing would ever be desired is beyond me. Also,the 60 cutaway was particularly helpful for the big carb sizes,but was also a big help for the Vitually all carburetor issues should be thought of primarily in terms of throttle opening,with thr RPM's a secondary consideration.

ALinHB
Cucciolo - the Lil Pup
Posts: 14
Joined: Thu Aug 20, 2009 3:00 pm
Location: Hawks Bay Napier New Zealand

Post by ALinHB » Fri Oct 30, 2009 11:44 am

OK OK OK
I am taking my 60/3 slides out to the rifle range next weekend.
I ve ordered a pair of 60/1.
I will give it a go. You got me convinced.

On second thoughts i better hold off on taking them out to the rifle range untill i give the others a run because these are new slides and the bike is actually running the best it ever has.

I have also noticed also absoluetly no difference in riding when I was playing around with fuel pumps settings on my 32mm carbs. May they rest in peace. The tuning could be slightly better on these new 36mm carbs. I get flat spot when powering on hard from about 3200 rpm but when it hits 4000 it takes off like a rocket.

Cheers Guys

Ray O'Donohue
Parallel Twin
Posts: 119
Joined: Tue Oct 13, 2009 8:11 am

Post by Ray O'Donohue » Fri Oct 30, 2009 12:16 pm

re "flat spot when powering on hard from about 3200 rpm but when it hits 4000 it takes off " : remember,always think of throttle position first when carb tuning,rather than engine speed,etc. If you are going from cruising (throttle essentially closed) at 3200,then whacking open the throttle,that is precisely where you need the accelertor pumps to squirt,for your vacuum at that moment has gone to almost zero.

pilotg
Diana
Posts: 51
Joined: Sat Mar 19, 2011 1:24 am
Location: Christchurch, NZ and Brisbane, Australia

Re: My base settings for 36mm PHF Dellortos SD Darmah

Post by pilotg » Mon Feb 23, 2015 1:38 am

Greetings from Christchurch, NZ

I too have a 1981 SD900 that I am converting to a pair of Steve's 36mm Dellortos. It sounds like you had the grief I'm having now.

I can get the bike to fire up, with the chokes on, every time, no problem. It doesn't seem to matter how long I warm it up as soon as i close the chokes the bike, farts, back fires and dies. It's really driving me nuts. No matter how warmed up it is the mixture screws do absolutely nothing.

I have the following, as supplied by Steve:

60/3 Slide
50 Idle
70 choke
130 Main
K18 needle, 3rd notch
300 (not sure what you call this one but it's the one the floats operate)

Can you let me know how you are going and what set up you finally went with please? I'd like to order some parts.

Many thanks

Regards

George
1981 SD900 Resto project

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