Re: accelerator racing under load only ...
Posted: Sat Mar 13, 2010 3:53 pmIf , as seems most likely from previous posts , with all other suggested causes being checked, the problem is due to air coming in via throttle spindles, are there any suggestions how I might check this ?
The detective work continues..........
We can eliminate the servo as we just blanked it off & racing + slow returning still occurs . Blanking off headlamp vacuum line doesn't cure it either. there's nowt wrong with throttle cables and return springs . I can see light down progression holes when I check.
We're talking about revs racing up to about 3000rpm and then hanging high for a second or two before coming down again when I drive a few yards down the drive and take my foot off accelerator.
carbs seem pretty well balanced with synchrometer on 7 for all inlets when on fast idle ( can't tell you rev's 'cos I'm standing over the carbs but probably about 1500 rpm , and about 4 at 700rpm.
In following the weber carb balancing instructions I note it says crack open the mixture adjustment screws about 3/4 turn and then fine tune in small increments until you maximise revs .
What i've found is that this works very well for front carb & the screws are more or less in the right position at 3/4 turn or so, but with the rear Carb I get maximum revs with screws right in but then it is a bit lumpy . I've found the best compromise is with both the rear carbs mixture screws out about 1/4 turn. Might this suggest that if air is coming in thru spindles that it is the front carb most likely to be the culprit? There seems to be no play in the spindles either at closed throttle or when butterflies are open, as far as I can make out .
If I had an MOT I'd be seeking professional advice ... I'm a little too nervous to venture out on the roads to get an MOT until this problem is overcome!
Any more suggestions guys?
RichC
The detective work continues..........
We can eliminate the servo as we just blanked it off & racing + slow returning still occurs . Blanking off headlamp vacuum line doesn't cure it either. there's nowt wrong with throttle cables and return springs . I can see light down progression holes when I check.
We're talking about revs racing up to about 3000rpm and then hanging high for a second or two before coming down again when I drive a few yards down the drive and take my foot off accelerator.
carbs seem pretty well balanced with synchrometer on 7 for all inlets when on fast idle ( can't tell you rev's 'cos I'm standing over the carbs but probably about 1500 rpm , and about 4 at 700rpm.
In following the weber carb balancing instructions I note it says crack open the mixture adjustment screws about 3/4 turn and then fine tune in small increments until you maximise revs .
What i've found is that this works very well for front carb & the screws are more or less in the right position at 3/4 turn or so, but with the rear Carb I get maximum revs with screws right in but then it is a bit lumpy . I've found the best compromise is with both the rear carbs mixture screws out about 1/4 turn. Might this suggest that if air is coming in thru spindles that it is the front carb most likely to be the culprit? There seems to be no play in the spindles either at closed throttle or when butterflies are open, as far as I can make out .
If I had an MOT I'd be seeking professional advice ... I'm a little too nervous to venture out on the roads to get an MOT until this problem is overcome!
Any more suggestions guys?
RichC