General FZD jetting

[timgarman]

Hi Folks

Can anyone let me know what the jet measurements for an FZD 32/28 are?

And I actually have an FZD 32/26, so if this is likely to be any different, pleases let me know.

(Chris, is this one for you?)

Thanks

Tim

 

[Bambino]

Hi Tim,

These are the jets etc. in my 32/28.

https://www.fiatforum.com/500-classic/423634-dellorto-32-28-fzd.html Post #15 .

As you know the jet values will vary depending on the state of tune as well as the carby type. However having said that, the jets that I used seem to be a common combination.

About time you got around to this the FZD is too good to be left on the shelf

Chris

 

[the hobbler]

Tim;
Delighted to hear that you have got to the next stage. As you know, I have got a fairly well tuned 652cc engine in the back of my 500, with a 32/28 fitted onto it. I have been doing some careful jet fitting sessions, and logging every change so that I know at all times what jets are in the carb. As Chris so wisely pointed out, engine tune will effect which jets are required (all the engines seem to require slightly different jets), but these are the jets that I have fitted at the moment, and the engine seems to run well, idle nicely and pick-up smoothly.
Main:--------------128
Idle:---------------40 (although I may yet try a 38)
Pump:-------------50 (with 6mm of thread showing below the adjusting nuts)
Air correction:----190
Emulsion:---------6747/3
I have a diagram (with description) of all the emulsion tubes and a drawing of the float, with adjustment values. I will put both of them into the post to you. 'Eurocarb' have pretty extensive range of jets in stock for the FZD--if you have any problem getting them, just let me know and I will sort it out for you.
With the (very) slightly smaller venture on your carb, you may have to run a tad leaner--only experience will tell. The only real way to set a 'non-standard' carb up is on a rolling road--otherwise you could **** around for ages! With regard to the choke--the jet controls the RATE of fuel enrichment and the pump-rod adjustment controls the AMOUNT. With the above settings my engine starts from cold (choke NOT set-up to use) with 2 slow pumps of the throttle--then crank and catch.

 

[timgarman]

Great, thanks Tom and Chris.

Just to add some info to this thread.

I had planned to get the car running with the existing carb and then fit the FZD to reduce the number of variables. However, we've hit some issues.

The car has been running and sounding good. If you've seen the video then you'll know we don't have the petrol tank in yet. Using a make shift funnel at the front of the car.

The ar only starts on choke, although does better once it's warm. It tends to stall after pulling away and especially if attempting a slight incline.

When running there is a flat spot. As far as we can tell, it's not petrol pump related. The carb has not been pulled apart but we're thinking the issue is there.

So the plan is to spend the time on the FZD. There are one or two parts missing off this, that I need to source. Let me know if any of this sounds familiar.

Just got the doors on – wa-hey!

 

[timgarman]

Hi Chris, I did download and print your excellent strip down of the FZD. But couldn't find jetting numbers?

And Tom, presumably your figures are specifically for your 652? (BTW – say hi to Anne for me).

 

[the hobbler]

Hi Tim;
Yes the jet settings I gave you are what I have in MY engine, but they would be as good a starting point as any. Look on the 'Eurocarb' site, go to 'car carbs' and then FZD---they have all the jets listed, as well as some levers--what are you missing? There will be an envelope in the post tomorrow with all the parts shown ( and numbered) and the accompanying parts list.

p.s. Ann says "Hi" back.

 

[timgarman]

Thanks Tom, very helpful as ever.

I'm missing the following:

21) Idle mixture screw and 22) the spring that goes over it.
64) Throttle lever
69) Choke rod
3) Pump jet (I have one but mine appears to be much shorter than the one in the Dell'Orto diagram
6) Needle and seat
28) Pump non-return valve

Numbers refer to the Dell'Orto diagram I can supply if you don't have it. I did find a company in NZ who have some parts for the FZD. I'll try them first. Then Europe will be next.

Also looking for info on the following to see if we need two adjust or replace:

57) Main jet holder (Jet 130)
4) Emulsion tubes Number 8 (or 0.8)
5) Air connector 190.

I'll check out Eurocarb. Any info you can supply on any of this would be helpful. My mechanic pal is a carb expert so we should get it sorted.

 

[Bambino]

Hi Tim,

These are my settings -

132 main
48 idle
50 pump
190 air corrector
6747-8 emulsion

The engine is a bored 652 (695cc) with larger inlet valves, a raised compression ratio and a sports cam shaft. It is balanced with a ported inlet manifold and a sports exhaust. It cold starts, hot starts and idles well and revs with no flat spots.
Also, I live in a subtropical climate about 60m above sea level.

As Tom has said, the only way you'll get it perfect is to book a morning on the dyno with a bunch of alternate jets.

Chris

PS: Tom, is your FZD now back together?

 

[the hobbler]

Hi Tim;
I will try and answer you queries one by one.
(1)--mixture screw and spring in stock at Eurocarb
(2)--throttle lever--no longer available (N/L/A)--you will have to borrow one (to give you a template) and make one
(3)--choke link--N/L/A--but it is possible to run these carbs sans choke (I am)--just 1 or 2 slow pumps on the throttle prior to cranking engine when cold
(4)--pump jet--in stock at Eurocarb---I have a '50' fitted
(5)--needle and seat--in stock at Eurocarb
(6)--non-return valve--in stock at Eurocarb
(7)--main-jet holder--in stock at Eurocarb--get yourself a small selection of main jets--125, 128,130,132 is a good starting selection (Eurocarb seem to have their main jet numbers screwed-up!)
(8)--Emulsion tube--I have found that the 6747/3 gives better progression than the 6747/8--but you just have to 'suck 'n see'
(9)--air-correction jet---190 seems to be the optimum variant--everybody seems to settle on this jet.
A common mistake is for people to think that if the engine hesitates on acceleration that it needs a richer (bigger) jet. This is not often so---with the accelerator pump coming into operation, hesitation is often caused by too RICH a mixture. I have gone down a couple of sizes with both my main and idle jets and the engine is pulling better and idling more smoothly. As I have said before, everybody seems to have a slightly different setting, which works well for them--but a session on a dyno is really the only way to set the carb up correctly--any other way is just p---g into the wind, with no guarantee of a decent result.
I have fitted a SU throttle rod (and ball joints) on my engine/carb--it comes with proper left and right-hand threads so that adjusting the rod is
just a matter of undoing the lock nuts and turning the rod--in/out.

Chris:- to answer your question---yes my carb is back together due to your help and generosity---I am however doing my jet experimenting with the carb that I got from Steve Gurney (in Cambridge) and will then jet my carb to match and re-fit it

 

[timgarman]

Thank you Tom, this will be really helpful.

Tim