Which carb(s) does the motor have? I am not aware of needles "MB"
(but I see them in the Moss catalog listed for carb # AUD 52...).
See this page for HS4 & HIF carb needles:
http://www.teglerizer.com/mgstuff/SUcarbs.htm
Also, try the easy/cheap things first. The dashpots should have oil of
about the same viscosity as the engine. Not sure what you mean by
"light oil".
Make sure the accelerator cable is properly adjusted. With the pedal
floored the throttle plates should be wide open. If the cable is
misadjusted the throttle plates may not be fully open.
To test for free movement of the carb pistons, unscrew the dashpot
cap/damper. Hold it slightly cock-eyed and pull the dashpot up.
Release the dashpot (remove the cap/damper) and the dashpot should
drop down smoothly and hit the bridge with a slight 'click'. If it
does not, remove the top of the carb (aka air chamber) and make sure
the seating surfaces are clean. Replace the top and tighten the screws
evenly. Try again with the screws just barely snug. If it is better,
tighten the screws evenly and test again.
If the dashpot will not drop smoothly after the above, remove the
cover and look inside for evidence of contact - abrasion/scratches.
Gently polish out any scratches - trying not to remove excess
material.
Finally, I once thought I had a fuel pump problem in my MGA, it'd
accelerate fine up to a certain speed but then wouldn't go any faster.
Turns out the AIR filters were so dirty they were restricting intake
air flow! (shame on me...)
Finally #2, how about the float bowl needles? If they are sticking or
partially clogged they'd limit fuel flow. Check float height while you
are checking the float needles.
http://www.mgcars.org.uk/cgi-bin/gen5?runprog=mgoc&a=&p=emg/su_carb.html
Eric Russell
Mebane, NC
http://home.mebtel.net/~ejrussell
----- Original Message -----
> I have a 1964 TVR Grantura that runs a MGB 1800cc motor and trans.
>
> The problem is when accelerating it goes fine until ONE SPECIFIC
> SPOT where
> it flattens out. Speed is maintained but no more acceleration, you
> can hear
> and feel it wanting more of something, like a high speed miss. There
> is a
> "Sweet spot" on the throttle where it will or will not do this, very
> definitive.
> Needles are "MB" (standard)
> Light oil in carb dash pots
_______________________________________________
Edit your replies
Mgs@autox.team.net
http://autox.team.net/mailman/listinfo/mgs
|