hi guys, ive a 2.0 abf running twin 45's it runs ok ish !! tick over is lumpy and when you are driving it changing gear the revs dont drop very quick, when i was adjusting the mixture just when i thought it was spot on it intermitenly revs on its own, the jets are as follow idle 65 f8 main f15 135 air corrector 160 pump jet 55 and 36 chokes anyone please tell me how these sound ???? also at about 2.5-3000rpm it feels like a missfire/fuel starvation/over fuel the fuel pump re is set at approx 2.8psi
Air leak, poor balance, linkage issues. Stumbling sounds like a progression issue They aren't critical on fuel pressure. Jon
Back off the central adjuster. Ensure each carb spindle is free and not binding. Then try and balance, You need a 'suckometer' device or a motorbike vacuum measurement on the downstream side. Jon
I'm no dcoe expert, I have just used them for nearly 35 years. Progression is the transfer from the idle jet circuit to the main jet circuit. You may need to try different idle jets or idle mix volume (screw settings). There is plenty of good poop on how the dcoe works on the net. Get the genuine weber manual if you can, its excellent Jon
This is a really helpful guide on DCOEs Idle fuel flow: Progression: Main circuit: And this graph shows the relationship between the different fuel circuits and engine speed, this is useful for pinpointing which jets may need changing:
Cheers for that link, going to be my bed time reading tonight I'm trying to get my westfield running properly and it's turning out to be a bit of a pain!
Fitted a new linkage....still the same !! Take a while for the revs to drop also its flat and missfires under load !!!
Is the spindle moving freely and returning to the stop position under it's own steam? If it's sticky it may not close immediately which could cause the revs to drop slowly. That's one potential cause out of many, ideally you should get a professional with the right equipment to set them up for you. I say this from experience; tuning carbs by guess-work is time wasted, you'll never get it right.
I have seen auxiliary venture upside down and back to front. If its me and an unknown set of carbs, I strip them down to the last bit and start from there.... Jon
Yeap.....spindle returning fine to be fair i can get it booked in on a rolling but allthough it may not seem a lot but he wants 120 to start !! So before it goes down that road i would sooner change anything i can first without the huge labour charges
As John says, you need to be sure that the carbs are healthy before looking at jetting. If you're happy with the carbs (i.e. bought them new or they've been rebuilt) then make sure you don't have vacuum leaks anywhere. Then follow basic setup; make sure that the air bypass screws are closed, very carefully set throttle stop position on both carbs so that the first progression hole is just covered*, set the idle mixture screws to whatever the nominal starting point is for your model of carb, adjust mixture screws for proper idle running and air bypass screws for flow balance at idle, use the linkage to balance the carbs off-idle. Vacuum gauges are essential if you want a good balance setup at home. If it were my car I'd with that lot before moving on to driveability. As an aside, you say it's an F15 emulsion tube? I'm under the impression this is an uncommon choice and gives leaner running at part load for a given jetting, which may explain why you have such a rich idle jet. F16 is a common choice for these. *There are a few different models of 45 DCOE, the biggest difference is progression hole positions, and this has a big impact on running. There is a correct throttle stop angle which should coincide with the first progression hole, if it doesn't you can either leave it there and get a lean condition coming off idle, or set it further open and have too much air flow at idle. Which model are yours? (it'll say 45 DCOE and then a number on the top cover, i.e. 18, 152 etc) There are 4 and 5 progression hole 152 carbs available that are the best choice for your engine, the wrong carbs will never run well.
Lots of usefull information and plenty to be going at. I had a brief check this evening after reading correctly the spindles maybe sticking on one or both of the carbs. I obviously was not checking correctly, is thete an easy fix for a sticking spindle ??? In the morning i will check and post what number dcoe's the carbs are
Best fix is a strip down of the bearing area, clean or replace the bearings and make sure that the components are properly lubricated. It is essential that the spindle nut (32 below) doesn't cause any part of the linkage (45) or spindle caps (86) to contact the body of the carb, as this will cause binding. If necessary put a thin washer underneath the linkage or cap to space it out so the parts don't bind when the nut is tightened. Ideally you'll take the cabs off and check that the butterflies are central in the carb as well, I've seen then off by a very small amount and they bind with the carb body as they approach the closed position. This can be rectified by carefully tapping the end of the spindle with a small hammer to centralise them.
I started off this morning getting right back to basics as per the link above and discovered it wasnt a bind but badly adjusted idle bar/balance screws preventing each throttle returning so i adjusted both off and started again and carried out the idle screw adjustment in 1/4 turns i also fitted a new regulator fuel filter and it is 100% better ticks over lovely returns perfect but is still a very slight flat spot at 2.5-3000 rpm But it is driveable now ???????? however ive noticed on tick over the glass bowl empties and it is noticable on the revs !! Should this happen ??
If it feels like it's going lean at 2500-3000rpm you could try an F6 idle jet, or go one larger on your main jet. But it's all guess work without measuring AFR. It sounds like you're at a stage where a trip to a specialist would be the best idea.
