Wots Wong Wiff My Webbers???

[RAd28]

having a great deal of trouble with my webbers (45DCOE) flat spotting JUST off idle, to me would make sense to check progression ports for and blockage, but there isn't anything, all looks fine and clear to me... engine runs relatively well at idle (fairly rough due to piss poor timing chains/tensioners etc), and pretty damn well up high.

tonight i was playing with it, and managed to stall it just by opening up the throttle the slightest bit... my theory is that when it stalled the throttle plates are open enough to cause a lean out to the point the engine won't run... but there's no way fuel isn't getting to the progression ports since it has to go PAST them in order to get to the idle mixture screw, and finally the port...

WHAT THE HELL IS WRONG?! atleast give me something else to inspect!

cheers

[MWP]

Possibly the accel pump/s?

[Cameron_Datto]

So has it ever ran 100% off idle or have you changed some thing to make it do it ?

Running cokes on the larger side can cause a flat spot off idle due to not having enough air speed as it goes through the transition from the idle circuit to the main circuit . there are a few trick s to improve this if this what causing the problem .mainly around 2000rpm +/- 500rpm

Also make sure that your AUX Venturis bolts are tight & not missing or someone hasn`t fitted the Aux venturi upside down.

if its Acell pumps not working , the symptoms you would find that the flat spot would be a lot worse with quick opening of the throttles
And with a slow increase in rpm with small throttle angles , there would be Little or no no flat spot .

Spitting back /poping back through the carbies is a good indicator of a lean mixture .
Also make sure mixture isnt on the rich side and over fueling are you using a fuel pressure regulator ?

Optimax fuel with a rich AFR`s will fowl Spark plugs , and will play up like a second hand lawn mower , and the only way to clean them is remove and burn the build up off the Plugs or replace them .

[RAd28]

have checked accel pumps, i get a nice decent squirt when i nail the throttle, and a slow drizzle when i ease the throttle on, which is exactly what i'd expect. flat spot is only there on minimal load, when i plant the pedal she responds accordingly...

i'd say the flat spot is happening JUST over 1000rpm, but not so far as 1500rpm... as far as i know there is NO aux venturi's at all from what i can tell the auxilary venturi's bolt onto the filter side of the carby, inside the inlet 'ram'... these carbies have had those dome caged filters fitted so the aux venturi and ram have gone by the way side.

she's also spitting and coughing out the carbys too, but i'm attributing this to poor ignition timing, or something related there. it only does it occassionally, and only since we played with the dizzy... haven't yet touched the jetting on the cabies, and she never backfired through the carbies before... i've tried to change the dizzy back to where it was, but it doesn't make a difference...

last tank of fuel was Mobil 6000 or what ever, second best, 95RON i think... not the ultra-mega-super-duper-full-cream one... just the povvo-but-still-want-my-car-too-run one...

took her for a proper thrash tonight, and was flat spotting like a son-of-a-....... would literally need to bring the revs up to about 2000-2500rpm (and keep them there) to get off the line... i can't imagine it being anything OTHER then fuel related 'cause if i pump the throttle it'll get over it, and go... but at the throttle percentage it does it, it would have to be the progression ports... but they're looking all good...

she's never run 100% on idle for me... but that's been attributed to the piss poor timing guides, chains etc.. they rattle like mad, gonna be replacing them before too long if i can...

[RO11LR]

Have you tried putting smaller jets in it ? I had 42mm DCOE's on my 3k which were way to big and did alot of what your describing , it was a bitch to drive between idle and about 3000 rpm but i took it to a weber guy and he put smaller jets in it for me and made much better , much more drivable

[willwal98]

Maybe have a check for some air leaks? Get a can of carby cleaner or even wate rin a spray bottle will do and go over all gaskets and air lines. Don't forget the the butterfly shafts on the outside of the carby.

If that checks out maybe richen up the idle a little bit, more a bandaid sollution though.

[RAd28]

haven't touched the jetting at all, would rather avoid it, since the problem hasn't always been as bad since i've had it... i may very well try some smaller jets though, can't hurt (much)...

been going over it looking for air leaks like a fine tooth comb... i know just what a prick they can be, but so far nothing seems to be standing out... i'll admitt i'm not overly familiar with the 18RG and or webber setup, only really started playing with either recently... how critical are things like the balance pipes (between each runner) if the carbies are synchronised properly? what about those aux venturis?


too top things off, last night after my proper thrash i was driving home, and the poor bloody thing just about died every time i tried to load it up, i had to limp home below 3000rpm other wise it would sound like a spark plug lead had fallen off... i checked everything when i got home, all the hoses incase something had come loose, all the leads, made sure they were nice and tight, but everything appeared to be good... i didn't kill the poor thing have i? was revving it pretty friggin hard too coming down Mt Gravatt at about 5-6000rpm most of the way

[RO11LR]

Also if they are soft mount webbers ( gasket between carbies and manifold are rubber kinda like big o rings ) cause these have a habit of cracking alot and it maybe getting air in through there ? i was always replacing them

[RAd28]

yeah, they're definatly soft mount... according to the manual i have, all DCOE webbers are suppose to have a "anti-vibration" gasket between them and the manifold... though i have no reason to suspect them as being the problem... will be doing some work on it this weekend so will have a good look to see if i can find any problems there.

cheers

[willwal98]

wonder if it could be a timing issue?

[RAd28]

yeah... i've been wondering the same thing... cam timing is flogged out, ignition should... SHOULD be pretty good... but will be replacing with elec ignition before too long too...

[ra_28]

I guess by reading this the engine was running ok before the orginal caribes were removed?? How long have the webbers been sitting round before you have fitted them?? Have you pulled your plugs out to see what colour they are??

[RAd28]

i bought the car not long ago with the webers already installed... so have absolutly no history prior to getting it myself...

have now isolated ONE problem, the one mentioned in post #7 (piss poor running under load/above about 3000rpm) the number 1 main venturi had come loose, the 2 screws that hold it in place have both vibrated out, and the venturi had turned in the throat...

SO... now i'm looking for 2 replacement screw to hold in the venturi... you'll know the ones i'm talking about if you have them...

still to find the flat spot problem, (unless the venturi was causing that too, all repairs pending test drive)

[75Ta22LT]

smash it with carby cleaner....

no.3 on the 4age had a bad blockage, made it drop revs hard off the mark...

18rg's run like shit when the timing chain is on the way out?

an yeh, fix the venturi

[Munki]

if it was running fine and the loose venturi didnt fix the problem i would...

make sure the carbs are balanced, you can buy a balance gauge for 80 or so and you will use it more than enough to justify the price if you have a pair of problematic carbs. (some people seem to have the world of trouble keeping some sets in sync and some are fine, no idea why never had the problem myself set and forget ). Then set the idle mix

second dissemble and check for crap through the float bowl and jets.

plenty more options but thats where i would start

Daniel.