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Idling too quickly

Posted: Mon May 08, 2017 3:26 pm
by rdmstewa
Good afternoon... by heck, he's getting formal!
Haven't posted in ages, managed to fix all the recent issues with the cheque book. Except this one. Had the carbs rebuilt by my local man and now the car runs well, but soots up the plugs in no time. It's also idling at about 1000-1100 rpm. I can't adjust the idle speed because the screw isn't even touching the stop.
Had it down at the local meet the other day and the general opinion was that there was "something wrong" - but we never got to a specific diagnosis.
What worries me is that the choke is fully home and there's a bit of slack in the throttle cable. So maybe the butterflies are in the wrong place. Is that possible? Could I be running on choke all the time and pouring petrol down the bores?
All ideas gratefully received!

Re: Idling too quickly

Posted: Mon May 08, 2017 7:18 pm
by tony
Seems that you have 2 problems, running too rich, wrong needles or out of adjustment. As you say, butterflies misaligned.Suggest that you take it back to your repairer and get him to do a proper job which is what you paid for. :shock:
Tony.

Re: Idling too quickly

Posted: Mon May 08, 2017 10:06 pm
by Dazzer
Yes the butterflies need slackening off and allowed to seat before fastening back up and re checking. You'll need to take the carbs off the car to do it properly.

Re: Idling too quickly

Posted: Mon May 08, 2017 10:39 pm
by atom
I hope that rebuild means new butterflies and axles in this case. Air leakage because of sloppy axles is a very common reason for idling too fast without being able to calm it down.

Re: Idling too quickly

Posted: Tue May 09, 2017 9:03 am
by Mike Stevens
Hi Malcolm!

Don't forget that originally, your carbs would have had poppet valves in them. These were supposed to open on overrun but only on overrun. Over time, it seems as if the springs weaken and they can open a bit on tickover. The general cure is to replace them with plain butterflies - or solder the old ones up!

If the carbs have been rebuilt with new (plain) discs, then it sounds like they've not been centralised properly. This is usually done by leaving the fixing screws loose and letting the butteflies 'snap' shut a few times. Then do the screws up!

Mind you, your man should know about all this!

BTW, I've just sent you an email.

Cheers,
Mike.

Re: Idling too quickly

Posted: Tue May 09, 2017 12:37 pm
by rdmstewa
Thanks folks - this is what I rather suspected, and it looks like I'm going to have to sack my man... he's normally very good but he let me down again the other day on something else. Unfortunately, despite understanding everything that's been said it's beyond my capabilities to take the carbs off, mainly due to the fact that my hands aren't what they were - age and all that :(
Time to wield the cheque book again! Nuisance, that, I'm trying to save up to get the rust in the screen surround fixed...
Cheers

Re: Idling too quickly

Posted: Mon May 15, 2017 1:08 pm
by pete lewis
if they have temperature compensators on the side they may be set open when they need to be closed at normal temperatures

held on the side with 2 screws, and sealed to the body with two O rings , the plunger inside needs to be seated closed, adjust by tighten the small nut on the bi metal strip.. its more important they are closed than exactly right. or idle speeds and mixtures cannot be set up.as they bypass air past the throttle plates

but yes check the t plates are fitted the right way round ( yes they are chamfered to seat when closed) and are centred ok

Pete

Re: Idling too quickly

Posted: Mon May 15, 2017 1:41 pm
by Mike Stevens
Malcolm's is a '76 'S' so should have HS6s. Were these fitted with temperature compensators like the CD range?

Cheers,
Mike.

Re: Idling too quickly

Posted: Tue May 16, 2017 8:57 am
by rdmstewa
Yes it does have HS6 carbs - I got the overhaul kits from Burlen - as I just specified the car then I should have got the right needles, I guess, and I would also have got butterflies with poppet valves. Probably standard spindles as well. I can live with the high idle speed, but I suspect I could be washing the bores with excess fuel, so it'll have to be fixed!
Thanks for all your comments...

Re: Idling too quickly

Posted: Wed May 17, 2017 3:42 pm
by rdmstewa
Well... there's a garage not far from me that has a '77 Minivan so I figured they might know about this problem... and I've just got the car back. It's now idling at about 750, going like a rocket and although I haven't checked it (it's chucking it down right now) I'm assured that the idle screws are now touching the cam. I don't know what this wonderful chap actually did, but whatever it was it only took him an hour. Obviously something was out of adjustment. I may well pay this chap another visit!
Cheers