How to tune my twin webers?!

Hello, few of you might remember about me viewing a mk1, well i bought it after a 3hr drive back in it I LOVED IT! the noise, the smell, the feel i must say i am very pleased especially after going down from a mk4! should of done it sooner!

anyway, i have twin webers and although they sound awesome, they are a pain  to tune, and they hate being kept at low revs which is a nightmare in traffic, so im possibly thinking R1 carbs. I dont care about MPG i didnt buy a mk1 to care about that nonsense haha, but first, does anyone know a place that can tune up my weber and do a RR session on it? I was going to try R tech but im not sure if they do carb'd engines! anywhere local to Birmingham really! thanks very much people!

oh and a few pics

 

very nice, i'd stick to webbers or dellortos over bike carbs anyday
cant help you out as for a suitable dyno unless you wish to drive to essex
good luck car looks tasty

You can tune them yourself… I just tuned my mates twin carbs yesterday in exchange for a few BBQ'd sausages and a tin of lager!

Without getting into swapping jets or adjusting the air flow (that's more complicated and you need a monometer)
You can adjust the idle mixture screws find them here… http://www.s262612653.websitehome.co.uk/DVAndrews/weber4.gif

Screw In for a lean mixture, Out to richen. Firstly warm the engine and then trim your idle adjust screw in so the engine runs slow enough for you to hear any increase or drop in revs as you adjust the idle mixture screws. One barrel at a time start unscrewing the idle mixture screw 1/2 a turn at a time and listen for the engine speed, it should increase in speed as you unscrew… If the engine gets very fast then adjust the idle screw again to lower it. When the engine stops getting faster as you unscrew, THEN start screwing inwards 1/2 turns at a time until the engine speed starts to slow, at this point you unscrew 1 whole turn and that's you're sweet spot. Do that for each barrel and then set your idle - that's it!

If a carb spits out the trumpet then it is too lean and needs richening. (screw outwards to richen)
You want a strong pulse from the exhaust and no rocking of the engine.
If the engine is rocking then the carbs will need balancing, which you do with a airflow meter and the screws that may or may not have tamper proof paint on. But that's another story for another day (if you're interested).

Nice ride anyways, looks cleeeeeeean! ..not keen on the wing vents though..

As above re the basic setting up, plus, if the basic jetting is wrong you'll chase your tail trying to get a result.

Post up the basic engine spec and the current jetting, along with the choke size, and we can see if the basics are close and/or improve on them prior to the idle setting up.

Bike carbs can be ok but can also be a pain due to most types needing stripping to change needles & jets.

Dedicated car carbs (Weber DCOE & Dellorto DHLA's) have a much broader range of adjustment.

Dispite the bad press, Weber's or Dellorto's dont need regular tuning as long as they arnt badly worn. One of the biggest problems can be the thottle linkage… poor quality cheap linkages can give lots of grief when old and worn and case inconsistant throttle settling… people then blame the carbs when in fact it's a linkage fault. The best linkage is the genuine Weber type.

Also… an often missed setting is the fuel pressure… to high will give a rich mixture and flooding issues, too low will give a  lean mixture, so this needs checking too.

JMRacing said

Dispite the bad press, Weber's or Dellorto's dont need regular tuning as long as they arnt badly worn. One of the biggest problems can be the thottle linkage… poor quality cheap linkages can give lots of grief when old and worn and case inconsistant throttle settling… people then blame the carbs when in fact it's a linkage fault. The best linkage is the genuine Weber type.

Quite right, most people are quick to blame the carbs for your car's problems just because not a lot of people know about them. Carbs really don't need much maintenance and you won't need to re-tune them for the seasons. You'll be surprised how sloppy you can be with the tuning and how well they will run. So check all your electrical / usual things before blaming the carbs.

Visit the linkage and make sure that both carbs are fully closed on idle. (Easy - just adjust the screw between the carbs).
Make sure they open together.  If they don't then your throttle shaft might be bent = bad times.

Those kind of carbs are popular on 1.6 / 1.8 crossflow type engines. Try and find out what car they were off and that will tell you (maybe) what they've been jetted for. If they're off of a 5.3 litre V8 then you might want to get some smaller jets!