SU carburetor choke mysteries explained

Many customers complain about cold starting challenges with their British car. Many issues can cause this symptom, but sometimes improper choke operation is the issue. In this video, you'll see how the choke is supposed to work when set up right.

[@MartinSage]

Gene Berg used to say that a properly set carb didn't need a choke. Gene lived in SoCal😎

[@paulv5283]

It is different arrangement for other SU's like the HD6 for instance which does not alter the jet position but utilises a separate auxiliary carb.

[@TrojanBus]

I'm wondering if I need to adjust the choke on my Spitfire. It starts up fairly well, with the choke all the way out, but then it wants to peter out and die after about 30 seconds. I need to repeat this about 3 times, with a rest in between each time that it stalls until eventually, with lots of revving it just about stays idling. Any ideas? Thanks. Rob

[@ianwilliams4787]

Helpful...I've twin SU s and I'm never sure if pulling the choke lever is making the mixture richer. It increases the idle speed, but the engine often struggles to start first time from cold.

[@MartinSage]

A choke will make your carb rich by cutting down the air. If you are having trouble cold starting then the carbs are not set right. If you live in Los Angeles I'd be happy to help you set up your carbs. No Charge.

[@asido057]

@@MartinSage how much too tune carbs

[@victormadrigal931]

How ore were can I ger a new set of carburators like those ones for a datsun roadster fair lady 1969

[@bishopmahorn447]

I need it new set for datsan sss 510 pliz

[@bonobo8680]

What about su HIF ?

[@kingkong2025]

why dontt my carbs have a return fuel system?

[@RimfireRat]

can that slack be removed by cable adjustment at the crabs ?

[@mattmeyer4066]

RimfireRat you want that high idle “slack” area. The cold start process is: choke to get it started, then run high idle until the car warms up enough to idle smoothly without it.

[@evanoconnell9448]

Hi. How much for a set like that?

[@bugeyeguydotcom]

About $1250 for new hs2 set with manifold and heat shield at bugeyeguyparts.com

[@evanoconnell9448]

@@bugeyeguydotcom ouch. Ok. I have a triumph 2500tc. Need hs4 Su's. Sell them?

[@frankstrobel4350]

I have hs4’s on my spitfire. Starts great cold or hot.....but my choke cable is stiff. They cable itself moves freely....it is the returns springs on the carbs...they are fairly strong. Anyone habe a similar issue?

[@SilverJ56]

I need to figure out why my Bugeye won't run right... I have to pull the choke out to have it idle. Will not run without the choke being pulled out all the way. It then will stay roughly running at 1500 rpm... Is there a simple fix without taking the carbs off and totally starting over?

[@mattmeyer4066]

Jon Schneider sounds like you need to tune your carbs, or you have a vacuum leak somewhere. This video has a good explanation of the tuning procedure: kzbin.info/www/bejne/i6TLao2ZYs2Bf6M BUT, if you have a vacuum leak you will likely find it very difficult to get them tuned, if at all.

[@SilverJ56]

Matt Meyer Thanks Matt!!!

[@johnpearson492]

I hope you get it figured out. I too had poor running issues for a long time until I found out that my spark plug wires were burned up where they connected to the distributor. Make sure you have ignition set correctly before chasing carb tuning.