Dell'Ortos?

discussion about the 750 Sport and '89/'90 900SS, which share many mechanicals with the Paso series
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Danielmc
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model: 750 Sport
year: 1990
Location: Taunton, England

Dell'Ortos?

Post by Danielmc »

Hi,

Having been riding my new 750 Sport for a month, I've decided that the Weber has to go. I'm no expert where carbs are concerned, and I do believe that this device can probably be made to function acceptably but I lack the time and skill to start meddling with it.

I've decided to buy a Malossi kit which has two Dell'Orto 40mm carbs on short manifolds. The question I need answering is whether I can remove the fuel pump and use a gravity feed on these carbs? I think that the float bowls will be well below the bottom of the tank, so I'm optimistic. Also, if I can junk the pump, can I remove all the in-tank plumbing and blank off the return?

Final point - Loudbike Steve talks about mounting split FCRs on "the Malossi short manifolds that came with the Sport", does this mean I can reuse the existing manifolds for the Dells without spending money on new Malossi manifolds?
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Maico88
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Re: Dell'Ortos?

Post by Maico88 »

First, you can run the dellortos without a fuel pump. However, if you are going to do that you must remove the lines in the tank. They are easy to remove, but would be very difficult to put back. I have run my Sport for quite a while with no pump. Second, 40mm seems to be a bit large for a bike to run on the street. I have 36mm dellortos and am quite pleased with the way the bike runs.
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ducinthebay
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Re: Dell'Ortos?

Post by ducinthebay »

yeah, what Maico says.

You need the Malossi short manifolds for a Pantah engine, or a Sport/Paso. (If you swap the stock manifolds on the cylinders, the front cylinder will be in correct orientation, but the back one will not be) Manifolds for the SS series and Monsters are only usable if you get the FCR carbs, which are actually down draft carbs. The Dellortos are side draft.

As far as carbs go, this is my rating for performance, but also it turns out, cost.
1. FCR ~ $800 -$1,000
2. Dellorto 36mm with accelerator pumps.
3. Stock Mikunis on stock manifolds from an SS or Monster. You can get this setup for $150 if you are patient.

However, I caution you that if you feel you won't be able to tune the stock Weber, swapping carbs isn't going to be much easier, unless you buy a new full kit that is set up for the Sport/Paso.

I have been running the Dellortos with the fuel pump and the return lines with no problems for years. One of the advantages of having the pump is that any additives you put in the tank get mixed rather well quickly.

Cheers, Phil
Last edited by ducinthebay on Mon Jan 14, 2013 3:58 am, edited 2 times in total.
Duc in the Bay
1990 750 Sport x2-Rosso Blanko (900ss copy) & Nuovo Nudo (Scrambler project)
1991 907 -mostly stock
2002 ST4s - Lots of mods.
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Danielmc
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Re: Dell'Ortos?

Post by Danielmc »

Thanks for the replies guys...

The "Malossi kit" that's advertised for the Paso and the 750 Sport only offers 40mm Dells. I agree they seem a bit bigger than necessary. Here's the link:

http://www.malossistore.co.uk/Prodotto. ... &C=1610964

I was drawn to that kit because it's cheaper than the FCRs, and seemed simple enough even for me to fit!

I'm in touch with the UK importer of Dell'Orto, and their guy reckons to be able to supply the carbs for less than the price listed by Malossi. Hence my question about recycling the Sport manifolds. I can always ask him if he can prepare a pair of carbs with 36mm choke size. Can either of you tell me what designation of 36mm Dell you've got fitted?

Also I'm drawn to the removal of all the stuff in the tank, but of course it would need reinstating if I ever wished to refit the Weber... Phil - do you run a pressure regulator on your bike, or do the Dells work happily with the pump and the return circuit?
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ducinthebay
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Re: Dell'Ortos?

Post by ducinthebay »

I run the pump with a 'T' in the system for the return with no regulator or restrictor jet in the line. You can see pictures on a post I did a few months ago with pics of my Sport. I do not have a petcock in the system, and of course no reserve.

The stock short manifolds both point up, and if you swap them, I think one of them works but the other does not. (If I can remember right)

I am running Dellorto 36 PHF carbs. They use the rubber boots to attach to the manifolds. There is another version that has the rigid mount and requires manifolds to match. If you buy the Malossi kit, they will give you the rubber boots, the manifold, a new Thomaselli Daytona 2C throttle, and cables. (or maybe a cable splitter and use the stock throttle)

I spent a few hours with a dremel tool making the Malossi manifolds fit the ports on my heads. They had a huge step and I smoothed out the transition.

If you get a used system, take the time to find some new o-rings. (voice of experience)

Cheers, Phil
Last edited by ducinthebay on Sun Nov 18, 2012 4:19 pm, edited 1 time in total.
Duc in the Bay
1990 750 Sport x2-Rosso Blanko (900ss copy) & Nuovo Nudo (Scrambler project)
1991 907 -mostly stock
2002 ST4s - Lots of mods.
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Danielmc
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Re: Dell'Ortos?

Post by Danielmc »

Hi Phil, found your pics and I really like your setup. With both you and Maico running the 36 Dells with good results I think getting a pair for my bike's a no brainer.

Couple of questions...

I'd prefer to run two cables from a new Tommaselli 2c throttle. What length did you use for yours? Are the cables listed as a part for another Ducati perhaps?

Were you able to run with the existing choke lever and a cable splitter?

I don't want to run with intake trumpets, and would prefer to use small K&N type pod filters - can I get a pair of these to fit without fouling the frame?
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ducinthebay
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Re: Dell'Ortos?

Post by ducinthebay »

I could not find anyone who made cables that fit the bike. Maybe you can.
I bought the universal throttle cable kit from the good folks at VenHill
[U01-4-150] Venhill Universal Motorcycle Dual Throttle Cable Kit @ $37.98
I made my own. Takes some time to get dialed in, but works great now.
I use the 2C throttle

I am using the stock choke lever on the bars, but I'm only choking one carb. I haven't taken the time to put the splitter in for the second carb yet. Another way is to just use one of the flip lever kind on the carb and reach down to flip it on. Make sure you buy the correct length, as there are two to choose from.

As far as air cleaners, I always prefer as big as possible for best flow, and smooth air coming into the carb. I used 2" rubber elbows to get nice big 6" long filters up above the engine. The air is cooler up there also when riding, and there's a ton of room where the old aircleaner used to be. Short pods will also be more restrictive, and there isn't much room to stuff them in. Some have, but it doesn't look very graceful to me. The added intake length also contains the fuel fog and improves around town performance. Do a search on Helmholtz resonator and see how an intake tract can help or hinder performance.

Cheers, Phil
Duc in the Bay
1990 750 Sport x2-Rosso Blanko (900ss copy) & Nuovo Nudo (Scrambler project)
1991 907 -mostly stock
2002 ST4s - Lots of mods.
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Danielmc
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Re: Dell'Ortos?

Post by Danielmc »

Brief update - as mentioned in another post on here, I've finally got my 36mm Dell'Ortos on the bike, and am waiting to get some cables made up for throttle and choke operation. Forward facing carb was tight for space, but I made a small bracket that moved the coils forward by 30mm, and I've managed to get a K&N type cone filter in the resultant gap. Not as efficient as Phil's long inlets, but a workable fix nonetheless. Can't wait to get the job finished and some dry roads to see how this setup compares with the Weber.
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ducinthebay
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Re: Dell'Ortos?

Post by ducinthebay »

Oooh, Aahhh. New carbs are pretty. It just looks fast.

Now that you have two carbs, you have a balance issue that needs to be managed. I used the TwinMax to balance the carbs, and adjust the cables to get them balance at idle and through the midrange. Makes a huge difference. You can also use carb stix or other manner. Search the archives for the "Ducati Cuddle" to get them close before you start it up. I did this, but found that the TwinMax helped dial it in further.

Cheers, Phil
Duc in the Bay
1990 750 Sport x2-Rosso Blanko (900ss copy) & Nuovo Nudo (Scrambler project)
1991 907 -mostly stock
2002 ST4s - Lots of mods.
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paso750
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Re: Dell'Ortos?

Post by paso750 »

as those filters are really small, weren`t there any oval tapered filters with the same height and flange size (meaning the oval type that doesn`t have the flange in the middle but offset) ?
What`s that unused connection next to the fuel line on the next to last picture ? The carb on the horizontal cylinder doesn`t have that.

G.

PS: the clutch line seems to be quite close to the header
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Derek
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Re: Dell'Ortos?

Post by Derek »

paso750 wrote: What`s that unused connection next to the fuel line on the next to last picture ? The carb on the horizontal cylinder doesn`t have that.
It is the float bowl breather. I think the other one is obscured by the fuel line.
paso750 wrote:PS: the clutch line seems to be quite close to the header
It is indeed.

I would think that the short manifolds should increase the power by increasing the revs at which peak power will be attained.
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Danielmc
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Re: Dell'Ortos?

Post by Danielmc »

Hi Gerhard,

Good idea - I'll give some oval offset ones a try (I know exactly what you mean). The unused connection is a small fuel vent pipe (I think), and there is one on the other carb. Should have some small diameter pipe on there - my Guzzi Le Mans has the same carbs.

Clutch line has a piece of fuel line taped over it to stop chafing against the valve cover, and seems happy enough. If I ever need a new line I would make it longer though.

Cheers!

Dan

edit - Derek beat me to it!
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paso750
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Re: Dell'Ortos?

Post by paso750 »

The problem with that clutch line is that if it touches the engine or runs close the the header chances are the brake fluid heats up a lot more. Worst case scenario would be that i.e. in traffic due to less air movement and cooling the brake fluid gets to its boiling point, the clutch lever will feel soft and you won`t be able to disengage the clutch.

There`s no need for a longer clutch line, just route it on the right side of the bike as it originally is.

Btw. I love your Ducati bevel valve covers. I had the same in silver but sold them :-(

G.
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Maico88
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Re: Dell'Ortos?

Post by Maico88 »

That is a really good looking sport. I have one like yours and I have taken ducnthebays advice and added 90 degree elbows. They fit very well, make room for large air filters and help the bottom end.

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Danielmc
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Re: Dell'Ortos?

Post by Danielmc »

Just a small update...

I've fitted cables to throttle and choke, but haven't ridden the bike yet - sub zero temperatures around here.

I did buy the Venhill kit, but the galvanised wire was much thicker than the oem stuff, and the attached "carb" nipples (EE7?) were too big to fit in the Dell'Orto carb slides!

I had a couple of Guzzi T3 throttle cables, and two small Guzzi V65 lower choke cables, so I decided to keep the original single cable from the throttle and using the Venhill splitter, graft it on to the carb ends of the two T3 cables. Likewise on the choke, I used the original choke cable and spliced that on to the V65 lowers using a Domino splitter.

As all the wires were now going to be stainless I spoke to a UK based manufacturer of soldering supplies who sold me the correct solder pellets, and a special liquid flux for use with stainless steel wire. Ebay supplied a Chinese made electric solder pot (for £14) which worked perfectly and after the fiddly job of measurement, the actual soldering of the nipples onto the wires went smoothly - dipping is far easier than using an iron and solder wire.

Hopefully I've attached the nipples well enough so they stay put, but so far I'm pleased that the cables run neat with no sharp curves, and I was able to keep the standard throttle and choke setup.
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