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WEBER CARB ; BASE SETTINGS ;
The following is an extract from an old Reliant World post by forum member " lone triker "
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Hi , I have seen a lot of people are fitting Weber carbs to their Reliant and asking what jet sizes are the best to start off jetting their carbs from , well after a lot of information gathering both off Reliant hillclimbers and a mate with rolling road these are the ones I have come up with for
Base line setting your carb up to run on a 850 Reliant with modded inlet and orginal cast exhaust manifold using a K&N airfilter on the Weber.
Weber 34ich with 25mm Venturi Jets are as follows :
Main Jet : 130
Accelerator Pump Jet : 50
Idle Jet : 57
Emulsion Tube : F2
Float Needle : 175
Air Correction Jet : 150
Throttle Disc ; 85 degree
For 24ich with 27mm venturi jets are :
Main Jet : 150
Accelerator Pump jet : 50
Idle Jet : 57
Emulsion Tube : F2/F6
Float Needle : 175
Air Correction Jet : 170
Throttle Disc ; 85 degree
These are base line settings and your reliant should be checked on a rolling road to check these jet sizes as each engine is different to one another as toolings worn over years of prodution and it depends on state of tune of motor and mods done to them as well.
If you remember a bit back I was going to fit a Weber and an SU to my trike to compare the difference on rolling road and I was surprised at the result.
The SU was bad on emmisions and only really came into it power between half and full throttle due to relying on the vacuum the engine produces to rise the piston and needle in the carb , whereby same trike with Weber fitted was lots better on emmisions and was on power earlier due to having accelerator pump to pump fuel straight into engine via carb quicker than SU.
This produced more torque low down to mid rev range so I think it was the better of the 2 .
As for top end speed the SU and Weber were very close with the SU winning by 5mph .
This was due to the carbs bigger venturi at top speed compared to the Webers limited venturi of 25mm to that of the SU's 32mm venturi on full open throttle .
As I tow with my trike I will be fitting the Weber carb as it is better for towing as the torque comes in earler than the SU and you dont have the annoying flat spot when you try and over take when towing if the SU was fitted due to have to wait for engine to produce more vacuum to make the piston rise and lift the needle up out of the jet.
So there you have it base line jets for fitting weber of 2 venturi sizes , but dont forget to have them check on rolling road for your individual vehicles.
Further info received from Noel Revbadtoad Bramwell
The only difference in my settings now is i have a F6 air correction fitted as i run a K&N airfilter and a 4into1 joe mason big bore exhaust system.as i found the F 2 did not preform will with this set up but F2 should be alright with standard manifold and exhaust system.
Dont forget these are starter guide lines for a webber carb set up as i told them you are better to get it checked on rolling road to make fine adjustment to jets as all engines are different to one another as reliant did not have much it the way of matching parts when building engines up on the bench ,hence some engines perform better from standard than others.so just for peace of mind and maybe a little more power and mpg have it rolling roll set up after getting it running on this set up.
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