With the engine switched off, if the piston does not fully fall with a
metallic 'clink' as it does so when raised and lowered by hand then you need
to centralise the jet as mentioned.
If it does fall properly, and it is only raised when the engine is running,
the throttle buttterfly is not closing for some reason. Slacken all
linkages on the throttle and choke bars - which is what you should do to
setup the carbs anyway - and if that fixes it then proceed with a full setup
from there.
If the problem is still evident then the butterfly is not seating properly
in the carb body, or if you have them, the poppet valve is not seating
properly. For the former try slackening and retightening the screws that
fit the butterfly to the spindle. For the latter try soldering them shut.
PaulH.
----- Original Message -----
From: Tom Wagner <twagner@pdq.net>
To: mg <mgs@autox.team.net>
Cc: Wags <tom.w.wagner@Central.sun.com>
Sent: Tuesday, February 13, 2001 4:02 AM
Subject: Carb problems
> To the Great Knowledge of this list:
>
> I have a 67 MGB and on Sat. replaced a
> SU 4 jet that was leaking on front carb.
> When I went to rebalance the carbs, I
> am now not able to reset the rear carb.
>
> When looking at the pistons I notice that the
> rear carbs piston is higher than the front carbs
> piston at idle.
>
> I also can not get the idle to set below 1500-2000
> even with the screws back all the way out on both
> carbs.
>
> Before taking on this little project the car ran great
> and idled around the 800-1000 rpms and sounded
> great. One final item is that the piston will move
> up and then fall back down, but I can not force the
> piston to come down even close to the front carb.
>
> Can anyone suggest where to look to start to troubleshoot
> this problem?????
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