Cold starting issue

[Flash]

Second picture

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Third picture

[Flash]

There you go Terry.

I had to disconnect the tappet cover breather to give you a better look. Sorry that the pics are so tight. It was tricky trying to get around the  master cylinder to get these images.

What I have noticed is that when I go to move the enrichment lever by hand it is pretty hard to do, so that might be why the cable is not able to pull it.

Could there be something wrong inside the carb that is making the needle seat so hard to move ?

[Steam]

There is a small self tapper that holds the lever to the jet holder. If you remove the screw (watch for the little washer) you can manually move the jet holder to see if it is tight. The lever actually sits over a spigot type thingy all the screw does is stop it from falling off. It is common to find the lever off the spigot thus unable to rotate freely making it hard to operate correctly.

[Steam]

Also if the bend in the cable is tight it can impede movement.

[Flash]

Thanks for the info regarding the screw and the jet holder Dave. I'll take a look at that tomorrow.

Originally the cable was taking a bit of a funny route, but I've now passed it through a different hole in the firewall so it has a nice gentle sweep to it now.

[Pete Power]

Is this a left handed carby?

[Flash]

How would I be able to tell Pete ?

If I stand in front of the Moke looking down at the engine the choke and accelerator cables are on the driver's side of the carb. Hope this makes sense.

[Terry]

Is this a left handed carby?

It is an 1 1/4" carby which has the float bowl on the opposite side to the 1.5" carby.

Tery

[Terry]

Hi,

The screw attached to the butterfly shaft looks to be set to close to the cam operated by the choke, normally I would expect to see the jet tube start to move before the butterfly moves.

The long spring hanging off the choke is an after thought by someone, the choke should operate without that so it was possibly added to compensate for an issue where the cable is unable to return the jet tube to the correct position, one possible issue being a bent jet tube in which case it might be related to your description.

I would disconnect the choke cable and the spring and see how freely the you can move the jet tube down by turning the choke pivot . If you operate it so the jet tube travels down as far as it will go then release it, the springs behind the pivot should move the jet tube back to its resting position, which if it doesn't can be a bent tube and or grit or crud between the two pieces of brass, the jet tube and the locating assembly. You are looking for stiff or sticky parts in the jet tube travel.

Terry

 

[Flash]

Thanks for this additional info Terry and for your insights in to what could be wrong.

Armed with the additional information provided I'll do some more investigation tomorrow and will let you know what I discover.

Have a good evening.

Cheers, Gordon

[Flash]

Morning Mokers,

Armed with the extra info supplied by Terry last night I attacked my cold starting issue with some serious vigor this morning.

First thing I did was disconnect the "choke cable" and the huge return spring installed on the choke cam by the previous owner. I also backed off the adjustment screw on the butterfly so that the fast idle only kicks in after the jet tube starts to move.

I then rotated the butterfly with my fingers until the jet tube had moved to its furthest point and I can confirm that the springs behind the pivot do indeed return the jet tube to its original position if I let it go. So that seems positive. The movement seems smooth. There is a slight bit of resistance, but having no benchmark I'm unsure how easily it should move.

I took some quick measurements and there looks to be a total of 20 mm of butterfly travel. The first 10 mm doesn't seem to do very much apart from pre-loading the return spring on the cam. It's the last 10 mm of travel that moves the jet tube. Does this sound right or am I experiencing excess travel due to wear somewhere ?

[Flash]

I then connected up the cable again and thought I would give it a go now that the huge spring is no longer adding to the load.

Unfortunately I got the same result in that the mechanism freezes up before the jet tube starts to lift. However, in doing this I did notice something strange. Each time before I reconnect the choke cable I straighten out the inner cable which seems to develop a slight bend in it under use. This got me wondering if maybe the solid inner cable is what is causing the issue, possibly due to the changing angle as the butterfly moves.

I rummaged through my bicycle spares and found a short length of a braided gearshift cable. It's not long enough for a permanent solution, but I connected it up to the butterfly using the original bolt with the through hole and then pulled on the other end of the cable and .... eureka !

The butterfly now rotates to the fully locked position and the jet tube moves freely under cable power. Could the solution be this simple ?

Seems weird as from what I have read in other posts on this forum the solid inner on the choke cable appears to be a standard thing.

Anyway, I'm going to see if I can cobble together a braided choke cable from the bits and pieces that I have lying around and I'll report back later.

[Terry]

Hi,

you are possibly mixing up the terms a bit. The butterfly is a disc attached to the shaft which you attach the accelerator cable and this rotates to either almost block or not the air flow as it leaves the carby. The choke assembly has no butterfly, it is simply a pivot attached to a lever that pulls the jet tube up or down.

You are correct in that the choke cable is normally a solid wire but given the spring behind the choke pivot should be able to return the jet tube to the resting position then the cable is is only required to pull things and not push them.

The fact your solid cable is/was doing a right angle through the locking nut and bolt does look odd. Normally this would be going straight through and the original fitting, not what you have got, would move freely in the arm and not cause any pressure on the solid cable as it rotates.

Terry

[Flash]

Thanks for setting me straight Terry.

Yes, as you point out I have incorrectly been referring to the little shaped metal plate that the choke cable attaches to as a "butterfly". Don't know why I did ... I guess it's shape just reminded me of a butterfly. ... sorry for my use of a confusing term.

After my last post I searched around for a replacement flexi choke cable amongst my bits and pieces collected over many years, but no luck.

However, my searching did give me a chance to ponder the problem some more. What was worrying me the most was the amount of play in the mechanism that meant that the jet tube would only start to move near the end of the cable travel. To my naive way of thinking this just doesn't seem right.

So I decided to remove the carb to get a close up look at the mechanism. After studying the mechanism more closely I can see that everything pivots on a central bolt with a little return spring wound around the pivot point. Sure enough nothing visible happens as you start to rotate the mechanism and then eventually the jet tube starts to move. I couldn't see any obvious sign of wear that would cause the slack so I decided to back off the pivot bolt to take the mechanism apart. With the bolt about half way out something (I'm not sure what) suddenly shifted and ... hey presto ... I now suddenly have a jet tube that starts to move almost as soon as you start to rotate the mechanism. Let the mechanism go and the jet tube returns to the normal position. I tightened the bolt up again thinking the problem would come back, but the jet tube and return spring are still performing correctly. Go figure ...

I've no idea what shifted, but it seems to have done the trick. I put everything back together again (including the original solid core choke cable) and gave it a whirl. In hindsight I should have primed the fuel bowl, but I didn't think of this till after, so it took a bit of cranking to get the fuel through. The Moke then started, but wouldn't idle. I adjusted the fast idle screw which sorted that out. I can definitely say that the jet tube shifting mechanism has never worked during my period of ownership as this is the first time that I have noticed signs of a rich mixture with the choke knob pulled out. A pulsing exhaust note with a bit of black smoke.

With the Moke switched off I engaged and disengaged the choke cable a good few times and the jet tube is moving perfectly now.

I'll let everything cool down and will try again in the morning. I'm hoping to report back with good news tomorrow.

Thanks for reading.