11 replies to this topic

[screech]

Iv got a weber 28/36 on my mini and it doesn't like starting from cold...

It will run on choke for a little while, then goes to a mis-fire sound, where i have to keep it going with the throttle...

If i push the choke in, it runs, then the revs pick up and it dies...

I really have to keep on the throttle until it decides its warm enough to keep itself going...

Im running megajolt ignition...


Anyone any ideas...


cheers

[Nightrain]

Will it start without choke ? Have you checked for air leaks ? Pay special attention the the secondary choke, these often stick open slightly. If it's not shutting it needs adjusting so it does. If all the above checks doesn't find any problems you'll need to look a bit deeper.

Next thing to check would be the idle mixture screw, it's the one near the throttle lever sort of pointing up at a angle. Screw it right in and then back it off two full turns.

If again still joy, check the float height. To do this remove the top of the carb, you'll see the brass floats, now holding the cover so the floats pivot point is at the top and the floats are hanging down vertically. Look between the floats and you'll see a lever that makes contact with the needle jet. Now tilt the carb top so the lever is just touching the needle valve not pushing it in only just touching. Now measure the distance between the top of the float and the bottom of the carb cover it should be 5mm. The easiest way to do this is to use a 5mm scrap drill, file 2 grooves in the drill to go over the seams around the floats. If you don't do this you wont get a true reading.
If it's not 5mm you'll need to adjust the lever, until you get the correct measurement.

[cap'n crunch]

What size is the idle jet on the Primary Choke?

Also check that the 2 parts of the choke that sit under the main gasket are seated properly and are not ajar.

Has it been proffesionally set up on a RR?

[screech]

Thanks for the replys... i will check everything that has been said this evening...

It is going to the RR on monday to get the MJ and weber set up, the thing that im worried about is that i will get there and itr will be running fine as it will be warm and he wont be able to see the cold start problem.

cheers

[Nightrain]

Choke should pretty much be sorted when the rest of it's been set up, webers don't use a choke as such. They use a enrichment device, which basically makes what ever set up you have richer, same principle really.

[andyapanel]

Ive got one of these on my kit car and the only problem is c..p clogging up the air bleed valves (near the base, one on each side). Whip them out(one at a time to avoid putting them back in the wrong hole) and give 'em a good blow through with your lips clamped tightly.

[WiredbyWilson]

i don't use any choke with my weber 40 - just keep it alive on the throttle (normally just off the drive) then it idles lumpy but idles!! and is fine by the end of the road!

sounds like a good tune should cure the problems!

[screech]

Ok i tried everything that was said, and it still didnt like it, iv got it warm now and it idles, its a bit and and down but im guessing it all just needs setting up.

So as i start to drive it, it coughs and splutters a bit, is there a way of richening/weakening the mixture or is it all down to jets?

cheers

[cap'n crunch]

other than the idle (which is part jet and part adjustment) it is all jets.

Edited by cap'n crunch, 02 April 2009 - 06:28 PM.

[Nightrain]

Yep pretty much non adjustable without changing jets, have you tried adjusting them ? What you need to do is set the tickover to 1000rpms. Now turn the idle adjustment screws in or out until you find the point that the tickover increased the most (only adjusting the idle mixture screw).
Then adjust the tickover back down o a reasonable level.

[cap'n crunch]

Also worth checking the Starting fuel and air jet. It sits behind the emulsion tubes and air correctors.

[Nightrain]

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