MG-Cars.info

Welcome to our Site for MG, Triumph and Austin-Healey Car Information.

Parts

MG parts spares and accessories are available for MG T Series (TA, MG TB, MG TC, MG TD, MG TF), Magnette, MGA, Twin cam, MGB, MGBGT, MGC, MGC GT, MG Midget, Sprite and other MG models from British car spares company LBCarCo.

MG MGA - Is this excessive wear on choke lever arm?

Thought I should start a new thread as things have moved on. Attached is a pic of my rear choke lever arm. The clevis pin fits snugly in the right hole, but as you can see, there is lots of room in the left hole (PO fitted the bolt shown instead, which is same size as clevis pin but with larger head, I assume because clevis pin just slips right through!). Is that normal, or is it excessively worn? And would that be the reason the jet doesn't return quite all the way up without a gentle tug on its arm by me?
Other things I have noticed are (1) When choke fully returned, there is virtually no tension in side spring, I assume suggesting the fulcrum in the link is too low because of the slack? (the spring itself looks ok).
(2) With the arm removed, should the jet slide up and down very easily or should there be some resistance. Mine slides smoothly, but with a fair bit of resistance.
Very grateful for any feedback - thanks.

GrahamMV

No, there is meant to be some lost motion before the lever starts to drop the jet.
Lindsay Sampford

Hi Graham, just read the rest of your posting. I think the best thing you can do now you've got this far, is to get your carbs off and overhaul them with gasket and jet seal kit. There could be crud in there or perhaps the jets are worn or badly tarnished. Judging by yhe makeshift "fulcrum", there is always the possibility that the previous owner assembled the jet seals incorrectly. Go for it!
Lindsay Sampford

The hole in the lever arm is intentionally oversize. Not sure how much resistance there should be moving the jet up and down, but would think if you can move it by hand the spring should also be able to move it. The springs on mine have quite a bit of tension even when the jets are fully up.
Jeff Schultz

What bothers me is that the hole in the lever arm is so large that the clevis pin will slip right through - hence PO using a bolt and washers instead
GrahamMV

Graham

Bottom line is that you can all the replacement bits from Burlen in Salisbury.

http://www.sucarb.co.uk/ExplodedImageClassic.aspx?pumpsearch=&ProductId=9956

Steve
Steve Gyles

The bracket that mounts on the carb has holes that just fit the clevis pin so it can't slide through the hole when installed correctly. One of the postings in this thread lists the size of all the hole in the arm. http://www2.mgcars.org.uk/cgi-bin/gen5?runprog=mgbbs&access=&mode=archiveth&subject=6&subjectar=6&thread=2006070310514317082
Jeff Schultz

Ok, thanks and I see the hole is supposed to be larger. But I still dont understand why there is no real tension in the spring. If it was a problem with jet assembly seals, etc, then wouldn't there would be tension in the spring, trying to pull it up against the friction of the faulty seals?!!
GrahamMV

Graham, if there is no tension in the spring when the jet is lowered, then it sounds like you need a new spring. In your previous posting about choke cable fixing, Dominic mentioned a choke cable restoring spring that anchored on the heat shield. This is not a standard item, the only restoring spring like that is the throttle cable restoring spring. The choke lever restoring springs (one for each carb) are mounted on the outside end of the choke levers and up to a hole in the "ear" at the bottom ot the carb jet block (see the exploded diagram on Steve Gyles' posting). If this spring is weak or missing you jets will definitely not restore.
Lindsay Sampford

Me again, the spring in question is item 52 on Steve's diagram. Hope this helps, Lindsay.
Lindsay Sampford

Lindsay, Thanks for your posts. I have both the choke restoring spring anchored to a fixing on the chassis frame as well as the 2 side springs. The side springs look in reasonable order and so I am wondering maybe they are the wrong size. I am going to spend some time on it today and see what can be done.
Graham
GrahamMV

Graham, remove that spring that goes to the chassis, it shouldn't be there and may be causing trouble.
Lindsay Sampford

There is a good chance your choke mechanism may not be properly adjusted (especially since the Workshop Manual hardly mentions how to do it). See here: http://mgaguru.com/mgtech/carbs/cb102.htm

IN short, adjust cable length such that the first 3/8-inch or so of travel on the pull knob does not move the main jets (reason for the oversize hole). Adjust the link between the choke arms so both main jets start to move down at the same time. Use that first 3/8-inch of free travel for range of adjusting the fast idle cam and screw, such that you get fast idle before fuel enrichment.

The short tension spring on the tail and of the choke arm should be enough to pull the main jet upward to the shoulder seating position when the cable is released. If the jet sticks in a lower position it needs to to be freed up. You might do this by pulling hard down and pushing back up repeatedly until it returns freely by spring force only. If it still sticks, then you need to disassemble the bits to polish the sliding OD of the jet tube, and maybe replace jet seals.

I installed Teflon O-rings for jet seals (more than 10 years and 100,000 miles back. They have never stuck or leaked, and I am very happy with this. For more information on jet seals (and sources) see here: http://mgaguru.com/mgtech/carbs/cb106.htm
Barney Gaylord

With the cable completley disconnected, the jets still do not return back up to their "off" position. The side spring simply are not strong enough to do the job. I guess that's why the PO put in another longer spring from the connection of the two arms down to the chassis member. But even that doesn't return them completely. I have pulled the jets out and cleaned them, replacing with a little oil, but it didn't make much difference. I guess that means there is too much friction in the jet assembly and that I need to replace all washers, etc.
Problem is that I have only had the car for a few weeks and really want to enjoy driving it a bit. Unless its a simple fix I am considering returning jets by hand under bonnet soon after starting up, and sending the carbs off for complete refurbish in the winter.
GrahamMV

Graham, overhauling the carbs is less than a day's work and fairly simple if you have the insructions, and they are available on line. If I lived closer I'd do them for you! There's certainly no need to have your car off the road for half a week let alone half a year. Is there no one near you that can give you a hand if you need it?
Lindsay.
Lindsay Sampford

Here you are Graham, go to this web site and click on "H Type Carburettors" and it will tell you what you need to know to dismantle, overhaul, reassemble and tune your carbs. I'm sure you can do it! http://www.sucarb.co.uk/Technical.aspx
Lindsay Sampford

I am working from memory on the SU carbs, as they are sitting in a crate in the cellar, so I defer to the folks with the standard setup.
dominic clancy

Lindsay, Thanks for your encouragement. But I fear it would take me very much longer as I am really only a novice. I have only just come in having worked on the car since lunchtime. But the good news is the choke no longer sticks, I also recenterd one of the jets that was sticking and tuned her up. She is running so much better. Very satisfying and very importantly, I have learnt so much.
Thank you to everyone who has posted replies as they were really helpful.
GrahamMV

Probably got stiff through lack of use. The little cork seals on the jets need to be soaked in petrol. If the car sits for a long time the petrol in the carbs goes stale and then evaporates altogether leaving the cork seals full of residues, dry and stiff. The only cure is to drive it lots....a tough job I know, but someones got to do it!
Lindsay Sampford

Lindsay, You are probably right as the previous owner only did about 100 miles in over a year (I have had it just 4 weeks now). I reckon I could manage driving it a lot. Are you saying its possible that will fix the cork seals, or once they have dried out through lack of use, that's it.
Graham V

This thread was discussed between 20/05/2009 and 22/05/2009

MG MGA index

This thread is from the archives. Join the live MG MGA BBS now