Tuning FZD jet sizes

[the hobbler]

Will "Hazel" who is trying to buy a FZD carb please contact me. Dave Porthouse has asked me to try and contact you as I have quite a lot of information as to what jets to fit to these carbs vis-a-vie the engine size and state of tune of that engine that the carburettor is going to be fitted to. [email protected]

 

[Mooster]

Will "Hazel" who is trying to buy a FZD carb please contact me. Dave Porthouse has asked me to try and contact you as I have quite a lot of information as to what jets to fit to these carbs vis-a-vie the engine size and state of tune of that engine that the carburettor is going to be fitted to. [email protected]

Hi Hobbler, I have just purchased a 32/26 overhauled original FZD for my 500. I have an Abarth 595SS spec 650cc engine (Cam/Head/valves, CR, exhaust etc. You said you have some jet settings, I haven't checked mine yet but assume it will need tweaking to suit.
Which emulsion tube do you advise and what is a good starting point?

 

[the hobbler]

Hi Hobbler, I have just purchased a 32/26 overhauled original FZD for my 500. I have an Abarth 595SS spec 650cc engine (Cam/Head/valves, CR, exhaust etc. You said you have some jet settings, I haven't checked mine yet but assume it will need tweaking to suit.
Which emulsion tube do you advise and what is a good starting point?

The Emulsion tube for ALL 500/126 applications of the FZD is :--6747-6. These are getting just about impossible to find in the UK (ALFA1750 in Italy has them, plus a big range of jets), but there is however a way around this problem---if you obtain a 6747-1 Emulsion-tube, which IS still available from "Classic Carbs" or "Eurocarbs" you CAREFULLY block-up the TOP 2 holes (1 each side)---you then have a 6747-6---simples. I used a local jeweller to do it for me, but whoever does it, make sure that the internal passage is still clear. The "Air-compensation" jet is a"190"---again, on ALL 500/126 applications.The 26/32 is an unusual version, so all I can do is to give you the jettings for a 28/32 on the "595".They are:---Main jet---128; Idle jet---38; Accelerator-pump---40. The '40' Pump-jet is as large as you want to go---any larger and the carb will be fine when the engine is cold, but will tend to 'bog-down' when accelerating away from lights, stops etc when the engine is hot (seen the video---worn THAT particular 'T' shirt--it can be quite embarrassing!). You will probably find that you can get away with a '35' Pump-jet.I have a fair bit of information regarding the FZD---if you would like to contact me direct ( [email protected]) and let me have your address, I will put copies of all the information that I have into the post for you. Having used one of these carburettors (a 28/32) on my 'enhanced' 659cc engine for about 10 years, I have found ways around some of the 'lack of parts' problems. If you want to give me a ring one evening (I live just outside Chester) feel free to do so--01244-683824

 

[Mooster]

Thanks Hobbler, it's great to have helpful, knowledgeable people on the forum, there are so many "I would or I think" comments from people who don't have a clue with no experience out there. When I have checked my jets, I'll get in touch. I'm currently having a few other stuttering issues when hot. I suspect that it's the 123 ignition failing when hot but I need to clarify what's causing it before changing the carb over
For info, I did try a "new" replica Solex 34pbic carb before this latest issue arose. Started and idled great, went like stink on large throttle openings but transition from idle circuit to main was poor. I think it was a "replica" carb issue so went back to the Weber 28imb which eliminated the problem, but the engine wants to really go but the Weber is restricting power and no pump jet!
I'll be in touch. Thanks again.

 

[the hobbler]

Thanks Hobbler, it's great to have helpful, knowledgeable people on the forum, there are so many "I would or I think" comments from people who don't have a clue with no experience out there. When I have checked my jets, I'll get in touch. I'm currently having a few other stuttering issues when hot. I suspect that it's the 123 ignition failing when hot but I need to clarify what's causing it before changing the carb over
For info, I did try a "new" replica Solex 34pbic carb before this latest issue arose. Started and idled great, went like stink on large throttle openings but transition from idle circuit to main was poor. I think it was a "replica" carb issue so went back to the Weber 28imb which eliminated the problem, but the engine wants to really go but the Weber is restricting power and no pump jet!
I'll be in touch. Thanks again.

As I have pointed out on a number of occasions--ALL of the "electronic ignition units" fitted to the 500/126 engines have one BIG enemy---heat. The 110/126 engines are unique in that the distributor is directly in line with the (sometimes, very) hot "cooling" air coming from the engine. This can, after a "enthusiastic" drive, easily exceed 100C--the wilting point (spelt D.I.E.) of all the electronic units, whether it is the expensive "123"units, or the cheaper "Hall effect" units. These engines were designed when "electronic ignition" was in its infancy (or for the 500---did not exist)---points are not affected by the heat, nor were the condensers built in that era. Most modern condensers are, to put none too fine a point on it--crap. One answer is to go back to points, and fit a "Competition Condenser" as marketed by Swiftune. These condensers have 2 leads on them--1 'feed' and the other 'earth', so they can be mounted up by the coil, and well away from the heat. The other answer if "electronic"is still desired, is to put a small 'hot-air-deflector' inside the thermostat-housing. I had a major running problem with an "electronic" unit, so devised and fitted this little deflector---so far it seems to be working well as, when measured after a "spirited" run, the heat of my distributor (measured with a 'laser thermometer' immediately after the run, and with the engine still running), has never exceeded 97C---enough below the '100' to let the ignition unit to survive---and a lot of that heat will be transfer from the crankcase. If you contact me direct ( [email protected] ) and let me have your address, I will put a copy of the article that I wrote regarding the "heat deflector" into the post for you.