Rough Running

[simplydelboy]

Beta 2000 Coupe, 1980, Weber DATR34.

I've been fiddling with this for some time, adjusting idle, throttle etc. I've now returned it to where I started, when I was getting hesitancy at low revs but running ok once I'd got it motoring. However fuel consumption was very high and once warmed up it idled at about 2000 revs. I've had the plugs out and they are always sooted up. Gave it another good run yesterday, and again ran alright once warmed up, but same old idling problems. Waffling around 750 when cold, up to 2000 when warm. Doesn't seem to be any leaks anywhere. I've checked all the posts I can find on the forum. Checked timing, all seems ok. Fuel filter looks fine, but I can't help thinking that either there's crap getting in from somewhere, or the carb is knackered. The curious thing is after the last run, I discovered that the two plugs nearer the driver's side are pretty much the right colour, but the other two are sooted up! Any suggestions?

I'm resolved to send the carb away for complete refurbishment if I can't locate the problem, and maybe even take the tank out, clean it and replace all fuel lines. On the refurb front, does anyone have any experience of Weber Carb Reconditioning Services in Chelmsford. The reviews on the guys website look good (of course they would wouldn't they), but the service does look good, and at £120, if it saves another weekend of sheer frustration then it's well worth it.

Expert help needed

Kind Regards, Del

[simplydelboy]

By the way, or is this BTW these days, I also found that the plugs used are NGK6ES. I see the recommended ones are NGK7ES. Would this make much difference?

[peteracs]

Hi

If you are getting high consumption and sooted plugs then fuel delivery is not your problem, I guess I would check

1) is the air filter recent and clean?

2) Is the fuel return line to the tank clear?

3) Does the valve in the carb float chamber work ok?

4) are the plug leads in good condition and reasonably recent?

5) if you time using a strobe is the advance working ok and how much variation, may point to disti issues?

6) have you cleaned out all the jets etc in the carb?

Hope that helps

Peter

[HFStuart]

The plug grade won't be the cause of your symptoms but it is worth changing them and the leads to make sure they're OK.

The fact that you have two plugs OK and two sooted suggests the carb might not be the root cause but that it's been set up to compensate for another problem.

I'd do the checks Peter suggests and swap the plugs & leads.

NB I always thought BP6ES were the correct plugs?
Also I do have a spare set of Magnecor blue HT Leads if you wanted to buy a known good set.

[rossocorsa]

if you don't have one buy a colortune great little tool for checking the actual burn in each cylinder. stripping the carb isn't difficult well worth doing yourself, use compressed air to blow through every jet and channel in the carb body then reassemble tune up and fingers crossed. I would also be suspecting the dreaded auto choke are you sure this is fully disengaging?

[simplydelboy]

Hi Guys

Fantastic quick response as usual. Thanks to you all. I've done just about everything suggested. The HT leads are just a few hundred miles old and the plugs were new. I've rebuilt the carb but will do so again. Also a Colourtune arrived in this morning's post so I'll get that on tomorrow. Today I have a date wiith a few mates at the local to watch Norwich v Ipswich. Neither are my team but my mates support each one and I've got a bet on. I'll keep you posted, and thanks again,

Del

[rossocorsa]

Check for inlet manifold leaks too if two cylinders are lean could be air leaks

[Neil-yaj396]

if you don't have one buy a colortune great little tool for checking the actual burn in each cylinder. stripping the carb isn't difficult well worth doing yourself, use compressed air to blow through every jet and channel in the carb body then reassemble tune up and fingers crossed. I would also be suspecting the dreaded auto choke are you sure this is fully disengaging?

This is what sorted my problems 18 months ago, though I didn't have an uneven plug colour.

Recently my warm tick over has crept up a bit and I'm getting some hesitancy at low revs, both after the winter lay up. My first move will be to clean and blow through the slow running jets.

I've never messed with the idle mixture, but I think the warm idle often gets set high to avoid stalling when the engine is cold. I used to do the school run in my old Coupe which had the warm idle set dead on, but in traffic with a cold engine I was always on the hand throttle (which my new car doesn't have) to keep it going between that cam on the auto choke dropping off and the thermostat opening.

[WestonE]

With 2 unbalanced cylinders you must check compression is even across the cylinders (within 5% variation hot wide open throttle) and check the tappet clearances (stone cold) are correct (.40mm inlet .45mm exhaust). I would have a really good look at the cams to check they are not worn (nose rounded). I brought a VX home that had all new carb, ignition and full fuel system and the Number 1 lobe on the inlet was seriously worn giving an uneven idle and hesitation. 

I hope it helps

Eric

[peteracs]

I will keep my fingers crossed it is not either of these suggestions from Eric.... Simply because of the cost implications, however should be checked for peace of mind.

Peter

[simplydelboy]

Many thanks all. I won my bet on Norwich but it won't cover the potential costs. Ah well, on with the Colourtune tomorrow and we'll see what that might bring to the party.

[thecolonel]

Lower numbers on ngk are hotter plugs and would be less
likely to foul at low revs, not quite as good as constant high
revs.
I use two steps colder as I have a heavy foot and don't idle
much.