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mk2 matt

bike carb question

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hi , when running bike carbs do you have to connect the choke or are they like Weber's and will run with out it

thank ian

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Mine would not start without a choke. Pull choke out ...start car first time...push choke back in straight away.

Eventually I made an electric choke with a small solenoid used to  automatically open car boots.the solenoid was 12v mounted on inlet manifold and used some of the rods that came with the solenoid.

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I am totally the opposite and have removed the choke linkage from my bike carbs. Car has no issues starting. 

Granted, if I've not started it for about 2 weeks, it cranks a bit longer, but will fire straight away the following day. 

I can see the benefit of a solenoid though. Good idea.

If you measure the holding current of the solenoid when it's fully engaged, you can put a resistor in the positive feed so it only receives the current it needs so not to burn it out prematurely, as a lot don't actually need the full 12v.  Wire the live of the starter/cranking circuit then so it automatically engages when you turn the ignition key to crank. 

Admittedly, this would also give you some choke on a warm engine, but it would fire up that quick that I don't think it would be an issue. 

Alternatively, if you do decide to use a choke then you could also use a traditional old school cable sourced from Car Builder Solutions for about £12.

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thanks for the conflicting advice 😀

got a set of r1 carbs on an st and started it for the first time last night. it took forever before it kicked into life, hence the question

for what it will take I might just connect it up 

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17 minutes ago, mk2 matt said:

thanks for the conflicting advice 😀

got a set of r1 carbs on an st and started it for the first time last night. it took forever before it kicked into life, hence the question

for what it will take I might just connect it up 

Won't be a big job and will more than likely help on cold starting. 

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As you can't 'cold pump' bike carbs like you can with Webers, and it's there for that very reason - why not use it? The 45 DCOE I used to have on my Cooper S had a 'choke / cold start' system built in from the factory - worked brilliantly! Flooding an inlet manifold with raw fuel isn't always going to work especially if really cold!

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