How much Choke?

satancom · Post by **satancom** » Thu Apr 09, 2009 8:09 am

Im back again with more inane questions

My land rover is running well, the temp is right and everything is sweet. Before changing my carbs for rebuilt ones I needed chocke in the morning to get her to start.. However now I no longer need choke and she fires up on the first turn and will idle happilly after a little rev or two..

I assuemd the carbs were set too rich as a cold engine shouldn't really start that well im sure. But after checking the mixture (using the lift pins) everything seems fine. Is it just a good starter or am I missing something?

Rebuilt 3.5 new rings, bearings, valves so on and so on

RoverP6B · Post by **RoverP6B** » Thu Apr 09, 2009 8:37 am

It is my understanding that an engine fitted with SU carburettors will always require choke to start the engine from cold if the carbs have been set up correctly.

If you engine starts when cold with no choke required, that does suggest the idle mixture setting is too rich.

When you raise the lift pins, the revs lift slightly then drop back essentially to where they were originally? If so, then the mixture is indeed esentially correct.

If the revs continue to rise without dropping back, then the mixture is too rich.

Ron.

topcatcustom · Post by **topcatcustom** » Thu Apr 09, 2009 9:19 am

When I had my mini I used to rally with a fairly big SU I never needed choke to start it...

satancom · Post by **satancom** » Thu Apr 09, 2009 9:30 am

RoverP6B wrote:
When you raise the lift pins, the revs lift slightly then drop back essentially to where they were originally? If so, then the mixture is indeed esentially correct.

Yes this is whats happening. Which Is why I believe the mixture is near enough. I will record the settings and have another go at setting it, maybe the idle is not set correctly, although it seems to idle fine, but I have no Tacho.

Its i very mild at the moment (for Wales) but its not exactly hot!

kiwicar · Post by **kiwicar** » Fri Apr 10, 2009 3:18 pm

Hi
I have had minis on SUs that did not need choke to start, both a pair of 1.25" on a 998 and a 1.75" on a 1100 with a long tube Ram manifold, both cases had the leading edge of the pistons rounded. Come to think of it the 4 SUs on the boxer manifold on my first 3,5 rover engine did not have the choke cable attached, again I had rounded the leading edge of the pistons (although I wouldn't ever say I had these set up right, but I always put it down to the rounded piston leading edge and the dodgy set up of the carbs).
Mike