Just fitted blackbird carbs to my Zetec. It runs fine and goes like the clappers but when you come off the throttle the revs hang on a bit to long
before going down. Ive got an extra return spring on the throttle pedal and the throttle butterflies themselves seem to be snapping shut quickly on
no throttle but the sensation persists. Anyone any thoughts?
Simon
Take your Divers Boots off before you go out in the car!
air leak?
You're actually running an F1 exhaust blown diffuser? 
Disconnect your throttle cable and try it by hand. Connect your cable and try again, both at the carbs, and poking the pedal. You may find that
there is sufficient drag in the cable/pedal to slow the closing down.
Air leak is the usual suspect....
The order I would tackle if the butterflys are definately snapping closed cleanly
Airleak check
use of a colourtune on each pot to check they aren't running lean
and a damned good balance
I had this on my (single cyl) motorbike recently
I stripped and cleaned the carbs and re-seated everything and it still did it
stripped down again - used rubber grease to aid the seal between carb and head...but it still did it
Stripped the carb AGAIN, no rips or nicks in the rubber diagphram and nothing seemingly gummed up/dirty or worn out
Re assemebled and re checked the float height - still did it
Couldn't identify any air leaks and nothing to balance (being a single!) and had me a bit stumped
making it run a tad richer by tweaking the idle mix screw out less than 1/8 turn seems to have cured it for me
I didn't have any over run popping or surges or coughing/spitting through the carb so I wouldn't say it was running lean when it was doing
it - plug colour was OK (light tan) as well - my engine must just be a bit fussy like that
If nothing else found I'd just fatten the mix a tad and see if its any better
(BTW the method I used to find "the initial sweet spot" for the carb's idle mix screw was start at 2 screws out from just seated and
turn it in or out till you find an "area" that gives the highest and "cleanest" sounding RPM and set the screw to halfway between
the "dips" )
This method is much more of a pain on 4 cyls of course, so a colourtune would definately assist getting this close
Good Luck
Regards
Rob
[Edited on 13/6/11 by robocog]
My zetec does the same just makes for faster cornering on change down
quote:
Originally posted by austin man
My zetec does the same just makes for faster cornering on change down
An old thread - but I also have the same problem.
The R1 carbs have a strong spring but maybe not enough strong.
Where and how should I attach the spring? Pictures?
I have put a strong spring on the pedal so the spring on the carbs is only having to return the cable
quote:
Originally posted by chris
I have put a strong spring on the pedal so the spring on the carbs is only having to return the cable