Rally 180 with Spaco 20/20 carb

Needing some help to get this Barn Find Rally 180 on the road. It came missing the original Dellorto Si 20/20 carb so bought a local Spaco SI 20/20 as fitted to LML or Bajaj.

I need to change most of the jets/atomisers etc to the original setting for it to run properly.

All I can find on the net is the original set-up for the Dellorto but not all the specs.


Main jet 109 this is Dellorto part no. 4576

Slow run 50 Delloto ??

Mix tube BE2 Dellorto part no. 5353 but this size is no longer available

Starter jet 60

Idle ??

Air correction jet ??


The Spaco comes with a one piece main/mix tube/Air correct jet with




And an Idle jet of 38-120 Dellorto part no. 9892


Does anyone know what the original Idle and Air correction should be as want to install Dellorto replacement parts.

Just an update, found that the the Air correct/mixer tube and main jet are seperated pieces not one piece as 1st thought.


So need to find out what the Air corrct jet and Idle size should be as per original Dellorto Si 20/20.

Thanks for info.  I see the BE2 had a greater flow than the BE3 I have. So I,m still wondering which Main jet is Best to go with the BE3. And why was it down sized to 107 instead of 109.

 And with my Sito plus 200 exhaust Which jet size would be a good starting point? My guess would be 110 or 111?


Thanks I will try 110. Next trip to Spain and Portugal so hot and at Altitude sometimes. will that mean I need a bigger jet also?  

the new si 20/20 which you have now is different from the old types. The rally 180 came with a 50 idle. The idle does not have a air corrector instead it is separate. On later si carbs this hole was blocked and idle jets came with an air corrector. If you have the newer type, put in a 55/160. it will be fine.



Hi I have a Rally 180 with a Older type Carb with Separate Idle Air intake And 50 Idle Jet.

 But my main jet is a 107 instead of 109 as in Manual.

 Also has a BE3 instead of BE2 Atomiser.

What difference has the BE3 to the BE2? And is this why the jet is Smaller?

 I recently fitted a SITO plus 200 Exhaust and trying to work out the best jet size to use after a seize on the Engine on the 107. But was also at Altitude?

Hi dude


I guess it´s like this:


Mainjet about - 108

Idlejet about - 50

Atomizer - BE3

Choke - 60




Thats the Differenz between the Atomizers:


BE 4, Area of all Wholes 06,28, (8 Wholes a 1mm)
BE 5, Area of all Wholes 08,28, (12 Wholes totally, 4x0,8mm and 8x1mm)
BE 6, Area of all Wholes 09,42, (12 Wholes a 1mm ), nearly same as BE 1.
BE 1, Area of all Wholes 10,08, (12 Wholes totally, a 4x1,1mm and 8x1mm)
BE 3, Area of all Wholes 13,35, (12 Wholes totally, a 4x1,5mm and 8x1mm)
BE 2, Area of all Wholes 20,41, (16 Wholes totally, a 8x1mm and 8x1,5mm)

You see, the BE 3 Atomizer is a richer Mixture, than the BE2.BE2 is the Richest Mixture you can get and BE4 the poorest Mixture.

you should be using a BE3 if you're not already. The 109 mainjet is stock, 107 could have been used for any reason: difference in altitude etc. With a sito + you should start at 112 and jet down if necessary. good luck.

110 should be anough, cause two numbers higher will be okay, if you only chanche the exhaust.

Thanks for that info. I have just ordered a SIP 0800 exhaust from this site as they say they are designed for touring. I wasnt that happy with the SITO plus and the way it did not fit correctly.

 Tanks again and I will keep you posted on my travels.


Bonzy, you got it on the nose, this is set-up like the newwer Si carb, so breather hole is covered by rubber, so will order the the 55/160.


much appreciated, we are still have a few months before we get to starting the engine but want to have everything set-up so we don't have any hassles.

Anything unusual on the 180 engine that we need to be aware of.

Clutch plates are similar to 125/150 or specifice to Rally 180??