Weber Tuning

[Gilb666]

Ok, so i've got my new shiny weber on, and everythings much improved as far as power and ability to start

I've been through the instructions 3 times now though and can't get the tuning right

When its sat on the drive being tuned, i can get it to idle correctly at ~850, but as soon as i drive it a bit, and pull up to a junction, it idles either around 1500 (2nd time it was tuned), or it stalls (third time), and the only thing that will keep it going is more choke - it does both nomatter if the car is warm of cold

Also, while the engine sounds smooth, the exaust now sounds like it could be attached to a beetle!

Am i missing something obvious?

[bensspares]

sounds like a weak mixture to me mate, are you sure the mixture is set correctly per the instructions.could be icing as the air temperature drops (not so likley yet !!!).does it do this with the factory airfilter housing installed or is it with the k&n filter..did you replace the carb mounting block and are you sure there is a good seal around that area.

ben

[RoccoGTII]

when mine was fitted the distributor had to be turned a bit.....might be worth think about? Timing etc...no mechanic but that was at sanspeed and this guy was pretty clued up.....

[Nate]

if you need to choke it, then you ain't got the mixture right. make sure the throttle cable is adjusted to let the butterfly close completely when you take your boot off

have you got the pdf entitled "base line settings dmtl" or something? easy setup guide to get it somewhere near. pm me your email address if you haven't and i'll dig it out and send it on to you

[fonzooorooo]

yep - mixture weak. I never got anywhere with mine till I got a CO tester... The mixture and idle speed seem to be kind of co-dependant... get the idle speed right, then, whilst altering the mixture till the CO's better, the idle changes. Whereupon you adjust the idle again... And it's all a waste of time if the timing's off. (ends up advanced more than "book" figure...) I set mine using the "advance till it pinks under load, then back it off a bit" technique... But if the mixture's weak, it'll pink because of that too.

Wecome to the nightmare!

I've got it in my head that the "extra advance" brings the "book" 16 degrees up to about 20 degrees... but I have that niggling feeling I may not have remembered that correctly... I'll point the strobe at it later... it'll get you a starting point.

As for actual CO, it's in the Haynes for each engine. It's 1% for the EX engine, mine wasn't happy at that (old engine, and all that) - I've ended up at 1.6%... It goes noticibly better if it's run a bit richer than that, but it uses more fuel then, and it's my daily... and I'm skint... hence the 1.6%

[Nate]

it's a black art. i watched one of the old guys at work setting up a carb and timing by ear a while back. most impressive to watch. after he'd done it had the probe up the bum which gave a CO reading 0.1% off the book value. burn him, he's a witch.

[bensspares]

as a guide read the post.....overheating/loosing water in the engines section of troubleshooting.all the info you need to set the mixture is there !!!..


ben.

[Gilb666]

Thanks for all the reply's, jstu got back froma weekend in blackpool so not had chance to play with it anymore yet, hopefully we'll get a few good nights this week!

[Gilb666]

Right, after much tweeking today, its running a lot better

Timing was retarded below standard setting, set to normal, then bumped up a little more unitl RPM stopped dropping off on power lift off (still dropping by about 50RPM for a moment before returning, but for now that's good enough for now, its not stalling!) also increased the mixture and reset the idle, generaly seems much better now. Couldnt find a CO tester for less than £80, so that wil have to wait (or might get my local garage to test it for me)

Still getting the weird 'put-put-put' sounding exaust note though, which must somehow be related to the carb as it didnt do it with the old Pierberg

[GT Matt]

You may want to check for an air leak.

Had the very same sound on my weber shod rocco and it was caused by a split vacuum pipe on the one-way valve that fits between the servo and the inlet manifold.

Will also effect power and ignition timing as it's on the same line as the distributor vac advance.

Matt

Ps - I'm not far from you and I have a CO machine as well

[Gilb666]

I've had a poke around, i can't see anything obvious, don't suppowe there are any tricks to finding where an air leak is coming from?

Would it be possible for me to use your CO machine at some point? will bring

[GT Matt]

Are you about during the week this week? I'm working at home on Thursday (weather permitting) on a friends car so could do it at the same time?

[Gilb666]

I have thursday and friday off work, so thursday would be great if that's OK!
Got to be in Birmingham for a gig that evening, so couldnt be later than 3 leaving, but other than that i'm free all day, so whenevers best for you

[GT Matt]

Come over around lunchtime of you want, it doesn't take long to set CO but I'll have a quick nosey around as well if you want me to. Should still mean you're away by 3.00pm.

If that suits I'll pm you my address

[Gilb666]

Sounds great to me dude