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This article addresses in detail the very common Dellorto SHA carburetor. Much of this was originally by Graham Motzing on his blog Fast, Cheap and Out of Control;


Dellorto SHA carburetors are common, cheap, easy to tune. They contain probably less than half as many parts as are in the carb in your leaf blower, but because of that they are highly modifiable, robust and easy to work with if you know some of the tricks.

SHA carbs come stock from a few different manufacturers. Mostly Italian brands, Minarelli, Garelli, Morini, Tomos A35 (very few A3) and some of the later model Motobecane and Peugeot.

There are Chinese clones available. By the time you finish tuning the carb, it really won't matter if it is a vintage or new carb, and the clones have been found to be adequately functional. The clones are available for $20 and up. The nice thing is that all the seals and needle are a decent quality. It's common in used SHA's to leak at the float needle.

Dellorto Jets are 5mm by .8, which is a commonly available size.

O ring that thing

One of the most misunderstood design features of the SHA is the design of the clamp and the proper way to mount the carb. Nearly all criticism of the SHA in one way or another stems from a basic misunderstanding of this process.

When looking at the clamp, you will see the mounting flange is split in two directions.

This allows the clamp to compress around the intake when you tighten the bolt. This clamp is not designed to provide an air tight seal. If you file the clamp or over tighten it, it will snap.

Often times, but not always, you will require a nylon shim to allow the carb to clamp tightly. This shim can, in many setups, create an adequate seal between the carb and intake, but it's generally safer to add the O ring as well and seal it the right way.

To properly seal a Dellorto SHA carb you will need to use a rubber O ring between the intake and the carb.

Get a proper O ring that will just fit inside the diameter of the clamp. When mounting the carb, maintain some pressure pressing the carb on the intake while tightening the clamp so the O ring seals well. Properly done, this will make it nearly impossible for a SHA to leak at the intake.

Slide tuning

The SHA can be tuned on the top end via the main jet, and uses standard 5mm round jets. Tuning at idle and low throttle is done by changing (or modifying) the slide. The slide cutaway refers to the carburetor circuit which controls the air/fuel ratio from one-eighth to one-quarter throttle opening on slide type carburetors. The height of the cutaway portion of the carburetor slide controls how much air is mixed with fuel, the larger the slide cutaway number the leaner the transition off of idle will be.

Ok so now we should probably discuss how this thing works a bit more. Fuel is flowing up through the main jet. When it is at idle and the throttle is closed, fuel is flowing out that tiny hole in the bottom of the slide slot. As you open the throttle you expose the other two holes and the fuel flows out of those holes. As air is passing the throttle slide it is going from high pressure low speed, to low pressure high speed, by Bernouli's principle. This is why the throttle cutaway matters, the cutaway will determine how much the air speeds up. When you put a slant on the bottom of the slide, known as 'cutaway' the air gets slowed down before it hits the emulsion tube. This has the effect of raising the pressure of the air at the tube, which reduces the amount of fuel that gets sucked up through the tube, in effect making you leaner.

This crappy drawing shows how the cutaway matters more at less than 1/2 throttle. You are in effect creating a nozzle, you go from a small opening to a bigger opening and as a result the air slows down. You can see above how when the throttle is mostly closed, the ratio between the front to the back is bigger than the ratio of front to back on the second drawing. This means that at low throttle, the air gets slowed down more, and the cutaway has more effect.

This is cool because 2 strokes tend to have a peaky power curve and therefore a peaky fuel delivery curve. When your pipe hits you are making more power and need more fuel (richer) than the linear curve that most stock-ish engines need. For most two strokes this means that the wide open throttle/ high rpm conditions require a dumping of fuel, but when the porting isn't flowing very well the mix should be leaner On more advanced carbs you can use smaller idle jets and an atomizer tube setup for progressive fuel delivery. On the SHA you are stuck with a relatively constant delivery of fuel.

Another interesting point about these is that reed valve engines (which as we know make more power in the low-midrange than piston port) will work better with the stock-ish flat fuel delivery curve. Thats why SHA's are popular among Peugeot and AV10 dudes, they run pretty good out of the box. For a piston port engine that has less midrange, especially if its a big kit or ported, you will need to modify the carb. This is also why, with PHBG or Mikuni carbs, reedvalve engines will work well with a 'four stroke' atomizer, which has a flatter fuel delivery curve, and piston port engines need the '2 stroke' atomizer.

So by mimicking that effect by changing the taper on the bottom of the slide, you can run a larger main jet so your top end is nice and fat, and your bottom end stays crispy. If you have ever ridden a Puch piston ported 65 or 70 kit with a unmodified 16 SHA you will notice the rich bottom end, this wont hurt anything, but it makes your throttle response on the low end poor and when you mod a stock small carb, it is really bad. Porting a stock cylinder can make this really bad, and the stock cylinder doesn't make enough torque in the low end to make up for it.

The size and placement of the emulsion tube holes also plays into the fuel delivery curve. Unlike carbs with needles, air bleed, and different emulsion tubes, the SHA is very simple: want more high-end fuel delivery, drill out the top hole, want more low-end drill out the bottom hole. Usually when modifying a 12mm carb to 16 mm or so, you will need to enlarge both of them some If you have a set of jet drills, which you should, just reach them in the intake there and drill it out, if you don't, you can use the corner of a file to slit them out bigger.

If you combine the progressive effects of cutting the slide, and drilling out the holes, you can play around with things enough until the carb works very well across the entire powerband. If you use jet drills you can stick the emulsion tube in once and forget it, if you have to keep pulling it in and out you will want to chew it up with some pliers on the seating area when you put it in for good, so when you push it in, it jams in there. It would be really frustrating if that thing was loose.

The Crazy Wayne Notches

From CW, to improve SHA performance and lean out the rich condition at idle:

Follow up: Added 4/24

This took me a while to get to, had a lot of projects get in the way, but very slowly over the last month or so I've been getting the Peugeot back together. The variator got modified to delay shifting and keep the engine in a higher rpm power band. The SHA got installed along with the intake manifold, and the engine got mounted back in the bike.

At first, the best i could do at tuning was to get it running ok-ish by drilling out jets and swapping around air filter pieces. The float needle was leaking like crazy, so fuel was pouring out and making the low end impossibly rich. It took a week for the needle to get to me, and with it some appropriately sized jets in the 60's and 70's.

This would be a good point to remind you, of course, that its absolutely necessary to have a properly functioning carburetor. All the parts have to work. This would seem obvious, but i've ridden bikes for people 'hey, can you ride this and see if i'm jetted right?' followed up by, 'oh yeah it leaks a little, you've got to rev it to keep it running.' Well, shoot, there's part of yer problem right there partner!

I've done dumb tricky stuff to try to save old crusty needles like filing a new point on them and shimming them up in the float with some beer can, but to be honest, its just not worth your time or mine. You will spend more than $5 on the gas you loose when you forget to turn your petcock off, and nothing gets you kicked out of shop spaces or gets people mad at you for parking your bike on the sidewalk, like a puddle of gasoline. Something about fire hazard, blah blah, yeah that too.


Other articles

Slection and tuning of Dellorto DHLA carburettors

bet on your baby dellorto

Selection and tuning of Dellorto DHLA carburettors

A very popular modification for RH7 owners is the fitment of twin Dellorto DHLA, these carburettors are very similar to the Weber DCOE range and not only deliver the goods but also look very good. A good deal of mystique surrounds Dellortos, specifically jetting and tuning. However Dellorto DHLA series carbs are not as complicated as you might imagine, and whereas there is no substitute for a good rolling road session to tune them, there is much you can do to tune them yourself, by selecting the correct choke sizes and initial jet settings according to a fairly simple set of rules. This should get the engine running to a reasonable standard in preparation for the rolling road.

Arriving at the correct carb/venturi size

When selecting Dellortos, the most commonly asked question is "Should I have 40s or 45s" coupled with "Surely the 45s will give more power". This shows a basic misunderstanding of the construction and principles of operation of the DHLA series. It is not the barrel size (40 or 45) which determines the airflow and therefore potential horsepower; it is the size of the main venturi or choke. Selection of the correct main venturi size is the first step in selecting the carburettor.

It is easy to make the assumption that biggest is best when selecting a main venturi size, but the purpose of the main venturi is to increase the vacuum acting on the main jet in order to draw in and effectively atomise the fuel mixture. The smaller the main venturi, the more effective this action is, but a smaller venturi will inhibit flow. A large venturi may give more power right at the top end of the power band, but will give this at the expense of lower RPM tractability. Only a circuit racer will benefit from this sort of compromise, on a road car, driveability is much more important. 95 percent of the time, a road engine is nowhere near its peak power, but is near its peak torque for 75 percent of the time. It is much more important therefore to select the main venturi for best driveability, once the venturi size has been selected, then the appropriate carburettor size can be arrived at.

Here is a small chart showing the available Main Venturi size for Common DHLA series carbs

Below is a chart that will allow the correct selection of main venturi size for engines given the engines capacity and the RPM at which peak power is realistically expected to be achieved, for road engines peak power is usually between 5250 and 6500, depending on the cam selection. After the correct venturi size has been arrived at it is a simple matter to determine whether 40/45 or 48 DHLAs are required, take the venturi size and multiply by 1.25, the result is then the ideal barrel size which will accommodate the venturi size selected.

Chart Showing Main Venturi Sizes for Various Engine sizes and RPM range

Carburettor Barrel size calculation

For example: a two litre engine giving its maximum power at 6000RPM will require a venturi size of 36mm, and therefore an ideal barrel size of 45mm (36 * 1.25), for this application 45 DHLA is the ideal solution. However a 40 DHLA will accommodate a 36mm choke, so if funds are limited and the engine is not going to be tuned further then 40 DHLAs will do the job.

If you have bought your Dellortos second-hand, it is important to understand that it is unlikely that they will be 'ready jetted’. However if you do not want the expense of changing the main venturis, you will still need to know their size, this is normally embossed on the venturi itself, so look carefully down through the main barrel of the carb from the air cleaner side.

Main Jet and Air Corrector Size Selection

A useful formula for the calculation of main jet size when the main venturi size is known is to multiply the main venturi size by 4. This will give a starting point for the main jet size which should be 'safe', again as a starting point the emulsion tubes can be selected from the table shown below, although for Pinto 7772.7 or 7772.6 will generally be OK. If your carbs are already equipped with these, then that will save you some money. Air corrector jet initial settings should be around 50 higher than the main jet.

Using these formulae, a venturi size of 36mm will require a main jet of 145 and an air corrector of around 190.

Below is a table showing suggested emulsion tube type, for a given single cylinder capacity.

Using the above formulae, the ideal settings for a 2000cc Pinto with power peaking at 6000RPM (290 degree cam or above) are as follows :-

7772.6 or 7772.5 Emulsion tubes

The 2000cc Pinto in just on the cusp of change for emulsion tube type between 7772.6 and 7772.5, if you already have 7772.6 tubes, use them it is not worth the expense of change, they will just cause the main circuit to start marginally earlier. A 2.1 or 2.2 Pinto should however be using 7772.5s although 7772.6s will do the job acceptably well.

Idle jets cause a lot of confusion; although their name suggests that they govern the idle mixture, this is incorrect. It is true that the fuel consumed at idle is drawn through the idle jet, but the idle mixture is metered not by these jets, but by the idle volume screws mounted on top of each barrel. The idle jets control the critical off-idle progression between closed throttle and the main jet circuit, it is this part throttle operation which is so important to smooth progression between closed throttle and acceleration and for part throttle driving. If this circuit is too weak then the engine will stutter or nosedive when opening the throttle, too rich and the engine will hunt and surge especially when hot. The technique for establishing the correct idle jet size is detailed later, but as a starting point 40/45 7850.2 idle jets for a 1600 engine 45/50 7850.2 for an 1800 and 50/55 7850.2 for a 2000 will get you out of jail free.

Below is a chart showing approximate idle jet sizes for given engine sizes, this assumes one carb barrel per inlet port E.G. two DHLAs.

Establishing the correct idle jet for a given engine is not easy but usually an approximation will make the car acceptably driveable. If the progression is weak then the engine will nosedive when moving the accelerator from smaller to larger throttle openings. A certain amount of change (richer/weaker) to progression can be achieved by varying the idle air jet holder size; this alters the amount of air which is emulsified with the fuel drawn through the idle jet. If this does not richen the progression sufficiently then the next jet size up, with the same air bleed should be tried. Below is a small chart showing the most commonly used air size designations, running from weak to rich. Generally speaking start your selection with a 7850.2 air bleed.

The ones in normal use are 7850.1, 7850.6 , 7850.2 and 7850.8.

Diagram of DHLA type carburettor

Setting the Idle and slow running

Rough running and idle is normally down to the idle mixture and balance settings being incorrect, below is a technique to establish a clean idle and progression. Before adjusting the carbs in this manner you must make sure that the following conditions are met.

i) The engine is at normal operating temperature

ii) That the throttle return spring/mechanism is working OK

iii) That the engine has sufficient advance at the idle speed (between 12 and 16 degrees)

iv) That an accurate rev counter is connected.

v) That there are no air leaks or electrical faults.

A reasonable idle speed for a modified engine on Dellortos is between 900 and 1100 RPM.

If you are adjusting the idle for a set of carbs already fitted then progress to the second stage. If the carbs are being fitted for the first time, screw all of the idle mixture adjustment screws fully home and then out 2.5 turns. Start the engine and let it reach normal operating temperature. This may mean adjusting the idle speed as the engine warms up. Spitting back through the back of the carburettor normally indicates that the mixture is too weak, or the timing is hopelessly retarded. If this happens when the engine is warm and you know that the timing is OK, then the mixture will need trimming richer on that cylinder. Set the idle as near as you can to 900RPM.

Using an airflow meter or carb synchroniser adjust the balance mechanism between the carbs to balance the airflow between them, if the rearmost carb is drawing less air than the front, turn the balance screw in a clockwise direction to correct this. If it is drawing more air, then turn the balance screw anti-clockwise. If the Idle speed varies at this point adjust it back to 900 RPM, to decrease idle speed screw in an anti-clockwise direction, to increase, screw in a clockwise direction.

When you are sure that the carbs are drawing the same volume of air, visit each idle mixture screw, turn the screw counter clockwise (richening) in small increments (quarter of a turn), allowing a good 5 - 10 seconds for the engine to settle after each adjustment. Note whether engine speed increases or decreases, if it increases continue turning in that direction and checking for engine speed, then the moment that engine speed starts to fall, back off a quarter of a turn. If the engine speed goes well over 1000RPM, then trim it down using the idle speed screw, and re-adjust the idle mixture screw. If engine speed decreases then turn the mixture screw clockwise (weakening) in small increments, again if engine speed continues to rise, continue in that direction, then the moment it starts to fall, back off a quarter a turn. The mixture is correct when a quarter of a turn in either direction causes the engine speed to fall. If that barrel is spitting back then the mixture is too weak, so start turning in an anti-clockwise direction to richen. During this procedure, the idle speed may become unacceptably high, so re-adjust it and repeat the procedure for each carb barrel.

After all the mixture screws have been set, the idle should be fairly even with no discernible 'rocking' of the engine, if the engine is pulsing, spitting or hunting then the mixture screws will need further adjustment. If the engine is rocking or shaking then the balance is out, so revisit with the airflow meter/ carb synchroniser. No amount of adjustment will give a good idle if the throttle spindles are bent or leaking air or the linkages are loose on the spindles!

Starting technique for Dellorto equipped engines (engine cold)

Some Dellortos have a cold start circuit (choke), others don't, in my experience, it is very easy to flood the engine and wet plugs using the cold start mechanism, as it very crude in operation. The accepted technique for cold starting is as follows:-

Allow the float chambers to fill if you have an electric pump, this should take about 5-10 seconds, fully depress the accelerator rapidly four times, then on a light throttle, turn the engine over, if it does not start immediately, repeat the procedure three times. The engine should fire, but may need 'nursing' for a minute or two before it will idle, gentle prodding of the accelerator should keep it alive long enough for it to warm up. If the engine does not fire within three attempts, then try five or six pumps. If this does not work, depress the accelerator fully and hold it open while turning the engine over for 5 to 15 seconds, then close the accelerator and try again.

When buying Dellortos second-hand ensure that they are a matched pair. Look carefully at the serial numbers on the top of the carbs, these should be the same, or very similar. If they are not then they are not a matched pair and may well give problems when trying to jet them, as the progression drillings could be different. Inspect the carbs very carefully before parting with your cash, check their general condition, check for fire/heat damage, check that the butterflies open and close smoothly and that the linkages are smooth in operation and the carbs don't stick open. A common problem with Dellortos is the attachment of the throttle quadrant to the spindle, these can wear and will give an erratic idle and progression which no amount of tuning will cure. It is important to note that Dellortos are very rarely 'ready jetted' so factor the cost of jets etc. when deciding on your purchase. Check the throttle spindles for wear, excessive wear here will bleed air into the engine and again will affect setting up dramatically. Servicing kits for Dellortos are relatively cheap so a neglected pair, provided that the above checks are carried out, can be restored to very good condition by a thorough clean and service, the servicing is not difficult but has to be done in a clean environment, using a methodical approach.

Jetting for standard 2000/1800/1600 Pinto on 40s

180 air correctors

40/7850.1 idle jets,45/7850.1 for 1800/2000

Jetting for modified 1600 Pinto on 40s

180 air correctors

40/7850.2 idle jets

Jetting for modified 1800 Pinto on 45s

180 air correctors

50/7850.9 idle jets

Jetting for modified 2000/2100 Pinto on 45s

Bet on your baby dellorto

bet on your baby dellorto

A video by Jim Snell, for 25 years, formerly a spokesman for the GasGas motorcycle company.

Jim discusses in detail, all the aspects of the Italian Dellorto .

Zdarec, konečně jsme byl schopen dotočit zbytek videa a nainstalovat tak dellorto na redbullku :) , v létě se pustím do pořádného testu spotřeby a podobně.

Обсудить видео и задать вопросы можно тут: Группа "Теория ДВС" ВКонтакте: http://vko.

В этом видео решил показать Вам, как настраиваются горизонтальные карбюраторы Dellorto(так же данную настройку. Канал ТолянЧИК ТюльпанЧИК ПОДПИСЫВАЙТЕСЬ наш сайт .

Swap with carburetor's instead serial intake.

Мы Вконтакте:

Tutoriel en francais vous permettant de comprendre le principe et le fonctionnement du carburateur Dellorto SHA 1515C. Rejoignez nous sur Facebook: Le .

Dissecting the Dellorto carb and taking a look at what makes it tick. How and where and what is emulsion? main jets? spray jets? etc. Find it all on You Tube.

Decided to upload a video for a friend of mine Hal on how to take apart and clean Dellorto 14.12 Carburetor for Tomos moped. The location for idle hole was not .

Сборка карбюратора Dellorto 19mm minarelli, процесс разбора в обратном порядке.

Сорян но видос собран из кусков, было мало памяти на телефоне.

Har monterat Dellorto - Förgasare (Black Racing) PHBG 21 mm på min Speedfight tillsammans med Doppler S3R avgasrör, 70cc cylinder och Polini . мы находимся тут и коментарии оставляем только там, под видео ныне отключены. карбюраторы.

Hi there. In this video I will be taking you through the steps for servicing your Dellorto VHSB 34 carburettor for a Rotax Max 125 go-kart engine. Produktvideo zu den Rund- und Flachschiebervergasern von Dellorto und Arreche. Erklärung der einzelnen .


Babetta 210 (1984) with carburetor Dellorto (2016). Babetta was a moped built in Czechoslovakia and commonly marketed under the Jawa name in other .

Babetta 210 With Dellorto Carburetor - Dellorto SHA 1412. Winter Start after 3 months without a start in -15 °C at 6 minutes.

Наш спонсор Супротек: Ещё видео про этот автомобиль: .

A tabletop review of a dual throat 44 IDF weber carb. Discription of where and what the different adjustment screws and jets do.

Наш спонсор Супротек: Первое видео: итого по жиклёрам: ХХ-58 ГТЖ-148.

Carburetor Dellorto dhla 40 disassembly.

Jet-Tech Pro Fine Tuning Part 1, includes a detailed over-view of how to configure Jet-Tech Pro to match the Air and Fuel flow characteristics of any Dellorto .

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