November 21, 2019 at 12:30 pm #429
We are working on Citroen DS restorations and mainly these cars were using Weber 28/36 carbs. Like DDE, DDE A1/A2, DLE A1/A2, DM depending on the gearbox and year. When we put these carbs onto a fully rebuilt engine many cases the idle is erratic, not smooth enough. During the carb overhaul we replace seals, jets, but we think it might be that the play of the throttle/spindle is too big and fals air is inducted that place and this is the reason for such erratic running at idling speed. If we set the idle mixtures correctly the CO and CO2 is within the factory limits.
But we would also like to get rid of the not fully smooth run at idle speed for sure. We think because by spraying startpilot spray around the primary spindle smoothes out the idle. Question:
1. Is it possible that not perfect idle caused by the excess wear of spindle and/or house? (it is around by few tenth of millimeter)
2. Is it rather the house that wears or the spindle?
3. If 1 is yes, is there any way to repair it w/o machining with repair parts/kit?
Many thanks for the tips, advices.
November 22, 2019 at 1:07 pm #431
Thank you for your message.
Yes, spindle and/or housing wear is very likely the cause of your erratic idle quality.
Especially so, for old carburettors and/or high mileage vehicles.
If the spindle is steel construction (Not brass), then the housing will wear first, as it is aluminium/softer alloy construction.
If the spindle is brass, then the spindle first, and perhaps the housing also.
There is no kit you can buy from us, to help you cure this.
It is a difficult task, but it is very possible to do.
First, you have to decide, which part needs machining (Housing, spindle or both?).
Usually, you will drill through the housing hole (The hole that the spindle goes through) to enlarge, but create a perfect round hole all the way through.
You probably need to elaborate on the drill bit. A standard drill might not be suitable. You need to have a ‘pilot’ in front of the drill piece to help you maintain the correct angle.
Anyway, the hole needs enlarging to maybe 1-2mm larger, and then you need to machine a suitable ‘sleeve’ or ‘liner’ and push fit into the new holes.
This will cure and repair the air leak.
Maybe try on a scrap/useless carburettor first, to get a ‘feel’ for the work.
Good Luck, and let me know if i can help further..
November 22, 2019 at 2:32 pm #434
Thanks for the response. At least that confirms our concern. I just don’t know how much tolerance (difference btw the shaft and housing is allowed – I mean when they were new) was allowed on the fit? Surely it must have been loose fit in order to have a free spin, but how much is normal? I am asking because not much excess (unwanted) air can ingress through such a small hole, but it plays role for sure as we experience during trying to eliminate it with temporary greasing or spraying startpilot. Like, if we move radially the shaft in the housing, is it visible I mean the play? Or if we see it is it already too much? Also we can measure it by gauge, but then what are the numbers relatively or by measure?
November 22, 2019 at 7:26 pm #435
I’m sorry but no one knows how much tolerance is required for this sort of work.
It does not have to be crazy. Just enough for the spindle to rotate freely.
The worn spindle/housing can be felt by opening the throttle half-way, and checking for sideways movement.
If your fingers can detect any movement – even a little – it will need re-sleeving.
Hope this helps a little.