Quote:
Originally Posted by RCHunt
I am awaiting a pair of KD needles, KNs were recommended but seem in short supply. The car is on ZH which comments on another forum seem to imply are too weak so maybe the cause of my problem, odd that they were original equipment on early P1800s though.
I set the mixture as in the Haynes manual, 15 flats down. I then adjusted around this point on both carbs, tick over settled to around 800-900.
Will try the WD40 if I still have a problem when the needles are fitted.
I have a rolling road session booked in a couple of weeks, for the moment I just want a set up which will accelerate on demand and climb hills!
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If your car is standard go to Burlens website, type in the details and it will tell you what needle you need. If it's not standard then it's trial and error with a rolling road and or with a O2 wideband sensor. I just use a wideband O2, very easy to check fuel mixture is where you want it under driving conditions. This will help you with needle comparisons.
http://www.mintylamb.co.uk/suneedle/
That might be the starting point but that's not how you set idle mixture. The correct way is to wind down the jet increasing fuel mixture until revs stop increasing then just back up one flat is the best and most accurate. A SU should idle rich, about 13.2:1 so when you back off the throttle when driving the carb doesn’t go lean and backfire. You can also use a O2 wideband gauge to measure the fuel ratio or a digital multimeter with a tachometer attachment to easily read the revs as you adjust the jet. Pic of mine attached, very handy tool.
I'd recommend 80 90 gear oil in the dash pots, make sure you have the correct spring in each carb, do a drop test for each carb (do a search on youtube for SU drop test) and make sure the needle is centered correctly.