Gary -
1) The "Fast Idle screw" is the exact same thing as a "Throttle Adjusting
screw." Both of these screws are able to set the size of the throttle plate
opening. On HD carbs this screw only exists on manual choke versions, and
is designed to only activated when the manual choke is on.
2) On HD carbs you ALWAYS adjust your idle using the "slow run valve".
Fast idle screw should be backed off and the throttle plates fully shut. If
the "slow run valve" adjustment isn't responding to turns for whatever
reasons, typically the o-ring on the valve is leaking air or the throttle
plate is not seating properly in the venturi chamber. A handful of people
swear to use the "fast idle screw" to set slow idle (in theory to keep
the venturi chamber from wearing out), but in my experience the venturi
chamber never wears and using fast idle screw to set idle just hides the
fact that your HD carbs have not been rebuilt properly.
3) On all SU carbs, the oil level is typically self regulating after you run
the car for 5-10 miles. You can over fill them by a bit (not too much) and
they will sort themselves out. Whether they have the vent hole or not is
immaterial. To check if you have oil in there or not, remove the dashpot
caps, pull them up, then push them back in. If you feel resistance for the
whole stroke, then you don't need to put any oil in there. If you don't
feel any resistance, then you need to top up with oil. 20 WT oil.
Alan
On Wed, Apr 6, 2011 at 9:16 AM, <warthodson at aol.com> wrote:
> 1. Were any of the BJ8 HD8's fitted with the mysterious "throttle adjusting
> screws" mentioned in some of the SU (Burlen) tuning instructions? Not to be
> confused with the "slow run valve", "fast Idle screw", "jet adjusting
> screw"
> or even the "plate retaining screw".
> 2. On BJ8's (multi-carb instructions) when no "throttle adjusting screws"
> are
> fitted, do you adjust the idle with the "slow run valve" as described in
> the
> SU instructions or do you close the "slow run valves" & adjust the idle
> with
> the "fast idle screw"?
> 3. The SU instructions say that "on non-dustproofed carburetters,
> identified
> by a vent hole in the piston damper top, the oil level should be 1/2" above
> the top of the hollow piston rod." It seems to me that any oil above the
> top
> on the hollow piston rod would slowly drain down into the bottom of the
> piston
> & then thru the transfer holes into the carb body. Does anyone actually
> fill
> their "non-dustproofed" carbs this full? How often does the oil level need
> to
> be topped up on these carbs?
> Thanks,
> Gary Hodson
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