8 replies to this topic

[mike.]

Right a few quick details:

1986 city e
998cc
HS4 SU carb

Last time i drove my car it was very 'chuggy' and there was no power - As if the choke was not pulled out enough - Even though it was. However it got me to where i was going and started up again in the same chugging fashion, then pretty much as soon as i engaged the clutch to pull out the engine just died and i couldn't get it started again. It sounds like a serious problem but it think all it is is the choke mechanism isn't working correctly and so isn't allowing the engine to warm up.

So i've taken a few pics to show what i mean.

When the chokes out it seems to be working fine:



But when i push the choke in, it goes in enough to release the throttle but then the cable goes slack like this and doesn't move the jet properly (i think its the jet?) which would explain why the car has been using sooo much fuel recently. :



But really it should return to this position where the jet assembly is lowered:




I noticed that the pivot bolt for the mechanism has worked loose and i think this has allowed the spring to come out of place on its lugs and so it just spins when the choke is operated rather than engaging the lugs and being put under tension so it can return the choke.

So i took the mechanism off the carb and studied the haynes manual to see if we could work out which way the spring needs to be fitted, but in the haynes the diagram shows the locating lugs on the opposite side of the spring - So its not much use.

Heres a pic of where the mechanism mounts with 2 lugs on the right of it:



Those lugs are shown on the left in the haynes manual so i can't tell which way the springs ment to go.

I thought it must have been this way:



So when the choke mechanism turns clockwise the arms on the springs engage on the lugs and are put under tension.

But when i reasembled the choke mechanism with the spring on this way, the spring still did not work and seems to just spin.

Heres a vid of the mechanism - I doubt it'll help but it helps illustrate the problem of how much extra movement the spring should provide:

http://s186.photobuc...ideo-0005_1.flv

Then heres another vid of the car running with the choke fully out. Not sure on the sound quality but you should be able to hear the car chugging away. It sound like its running at about 500rpm rather than about 1200rpm when the chokes out:

http://s186.photobuc...ideo-0006_1.flv

I don't understand this because the choke seems to work fine when its out but just doesn't return properly. I don't know what can be causing this.

So really i need to know which way this spring goes on so i can get full choke operation, then i can see what else could be causing this chugging...

[Ethel]

I bet you wish you took those piccies before you dismantled it


There was a similar thread with good piccies a bit back.

The choke lowers the jet when you pull the cable: when you accelerate the needle comes out of the to allow more fuel, so lowering the jet does the same.

Check the jet moves freely in and out of the carb.



I note you've got a waxstat jet may be that's having some effect as it's so cold at the moment?

[benb12]

So the jet isn't returning to it's original height when the choke is in and is causing it to run rich?

Perhaps the mechanism was just stiff and needed freeing up?

I wish I paid more attention when I dismantled mine today as I could have told you which way round it went.

When it was running did you try pushing up on the base of the jet to see if it could go up any more?

[mike.]

Right well tommorow i'll see if the jets moving freely without the choke mechanism attached.

So when the engines warm and ive got the choke in the jet is up?

Because when i pull the choke out this raises the jet i think... :S


So whats a waxstat jet as opposed to a 'normal' jet?

[Ethel]

DKLawson's just done a topic on waxstat jets, you'll get the idea from that. You should've whipped the carb off then you could be sat at the kitchen table in the warm .

You can see the jet clearly in your last piccy the brass tube bit should slide all the way inside the brass mixture adjustment nut until the shoulder touches the nut when the choke is fully in.

[mike.]

Right i see. I'll try and find these threads your talking about and have a read through them tommorow.

Any idea which way the spring goes on?

[Ethel]

I can never remember exactly, couldn't find the spring fitting thread either. If no one else stumps up I've got an old HS in the garage I can look at.

Had to go have a look since you put it in my mind

The last pic isn't far off - the L shaped end of the spring goes against the round post on the carb body just above it. the other end sits to the side of the lug that's bent towards the carb

 carb_assembly.bmp   1.4MB   79 downloads

[Ethel]

There you go - one naff drawing the spring obviously goes behind the green lever thingy.

Attached Files

•  Photo_0008.bmp   301.05K   37 downloads

[mike.]

Cheers for that - I can see what your saying now. I'm going home from uni for the weekend in a couple of weeks so i'll have another go then.