Carb slide advice Spanish/Italian or Jetex??

[Fireman Ash]

I am fitting a 42mm AF Clubman to my '82 Serveta Jet200 Ser.80 which has a SH1/20 Dellorto Carb (under Spanish license)

I have been advised to upjet the carb and replace the existing carb slide for one that is flat sided on both sides to rich the mixture at mid range.

It would seem that the Jetex carb slide replacement is too big in size to fit and I'm told that the Italian Dellorto match for this one is shorter e.g the 5914/1 type.

Would anybody have any idea if/why the Spanish Dellorto slides are all shorter in length (it's the same width as Italian one) and what may be a suitable replacement other than keeping the original one or fit a 22mm Jetex carb? I'm advised that I can up-jet and keep the existing SH1/20 carb slide however may experience some pinking at the top end of 3rd gear? I've yet to confirm this as the engines just come out for its rebuild.

Any help or advice would be appreciated.

Feel free to email me here or at fireman.ash@hotmail.co.uk

Cheers all

Ash, Torquay

[J1MS]

The cut away on these slides has little or no effect at the top end of the rev range. its biggest effect on the venturi is at lower engine speeds, and most of its effect will have diminished by about 1/3 throttle openings, by the time the throttle is opened to half way the choice of atomiser and size of main jet will have a much greater effect on the fuel being metered through the venturi, than the slide....
When using 22mm (SH 2/22) wheather reamed out or std I have sometimes used 150 slides ( -2) in place of the 200 slides( -1) when upjetting the carb, as it lets a bigger pilot jet run smoother as you accelerate, as some 22mm carbs become too rich with a 48 pilot and large main jet, and start bogging down at low to mid range. but when I have done this it hasnt effected top end just weakens the first 1/3. while richening up the carb with a closed throttle when you shut off through the bigger pilot jet. i.e. when going down hill. But you are right in what you say the cut away in the slide is there to weaken the mixture, but only at lower carb venturi/slide openings..
IMO... a Jettex if it works well, is a very cheap alternative to anything Italian. They can be faulty from new, but they do usually work well, and being very easy to set up. and at about £20 very cheap....

[Fireman Ash]

Cheers for that good advice.

The standard 200cc SH1/20 carb that I have has the standard atomiser with a 105 main jet, 45 pilot jet. I have been advised to replace the 105 with an interchangeable Jetex 122-124. Equally I've also been told that the Dellorto 105 may be sufficiently rich compared to a Jetex 123 as I understand the Jetex carb has a larger carb body, float bowl etc. hence why the replacement carb slide is bigger I guess.

So would it be sufficient to leave the original Dellorto carb slide and main jet and/or maybe up jet the main jet from 105 Dellorto to 122 Jetex?I guess it may be fit the Clubman and suck it and see so as to speak?

Cheers

Ash

[J1MS]

Normally a 122 would be way too big for that carb. you might need a smaller jet but start big and work down, less chance of a seizure, if you have a spare slide you could fill in the cut away at the back of that slide and see how it effects the jetting. You could use Devcon filler, just make sure it sticks and smooth it off as best as you can so you dont have to start filling the slide after. These types of carbs always seem to run better through an air box...All the best

[onefortheroad]

I noticed looking on Allstyles website last night they sell a Jetex 22mm that they rework themselves to make more reliable- might be worth the extra 15quid to buy a working one!

[rog60]

Although not a carburation expert, I have experimented with various Delorto and Jetex carbs on my Indian GP200 (stage 4 with 42mm clubman exhaust. The newer Jetex carbs seem to be better and also work 'straight out of the box'.
The Jetex on my set-up seems to be better with a 118 main jet and 47 pilot jet. I also have a delorto 'Spaco' SH2/22 which works with a 120 main jet and 45 pilot jet!
I also had a 22mm Jetex reamed out to 25mm and 125 main and 45 pilot works. I have also discovered that Delorto 2/22 slides seem to work better in a Jetex than the indian supplied slide and that genuine Italian jets are better calibrated than Indian ones so I have changed the atomiser, slide and all jets in the Jetex to Italian make.

Perhaps you can make use of this information. But mixture on these kinds of carbs is generally adjustable only by changing the main jet.

[Special X]

108 main and 48 pilot is all you need to do.

[Fireman Ash]

Thanks for all your help guys

Ash