Would you say it's now richer at bottom end (overlap)? It should be as the mains will come in at lower revs. Some say larger main airs will reduce the overlap by delaying the mains but I found that was very fine adjustment compared to changing the vents. A smaller idle jet will obviously lean the overlap where both jets contribute. If you did that main stacks out thing, you'd find your van drives just fine on 45 idles BUT will be almost impossible to start from cold! So there you have it. 28s should be quieter at your low speeds which can make you think it's running better - rich = quiet. Float height - did you check and set them? Were they correct to begin with? - makes a big big difference down at the low end. Lastly, if you were running the 127 with 30 vents and it wasn't too lean, you should probably go down at least one size with 28s.
Its good to strip any carb and stand in a can of MEK for a few days to dissolve any blockages in internal passages, then systematically blow through all of them with compressed air or carb cleaner, checking that they are all clear. Replace all seals and gaskets using a good quality kit. Beware cheap rebuild kits, they are usually imported taiwan or chinese rubbish. Often the o rings aren't even suitable for petrol and swell dramatically or crack and dry up. Once you have properly cleaned and sealed the carb, this will give you a good starting point. You can never get a carb to tune right if its not clean and properly sealed. Think very carefully before drilling out stuff...you may improve your carb, but equally as possible to turn it into junk.
Do you mean me? I did think very carefully but as these carbs came in two versions with different sized progression holes, it wasn't exactly blind experimentation.
Good point re floats... set some years ago and possibly wort a revisit as frankly someone did it for me. will look to come down on the mains a little. cant hurt! i much preferred the 28s btw. much nicer to drive and yep... doesn't sound like its trying to be sick when you floor it but cant recall swapping out the mains and looking through the box of dell delights the nearest i have are 145s i think so i might have done.
I think I might have some 125s - I'll look when I get the van back and send them your way with your 34's if I have. The floats definitely worth a look as the Dell book method only works for one type of float valve so confusion is more than possible. Dell book method on mine would cause very low fuel level for example. For the record I think you're a bit mad not to have checked while you had the tops off to change the vents!
lol. vents got swapped ages ago and it was a back to back test so I didn't even consider the floats. Will get my head around that when i have the time and ask the question on the best approach to that i guess. Good opportunity to sway out the needles to so best get set up for that. Happy to blag some 1225s off you for a try if available. we possibly should start a dellorto swap shop or sell stuff as I've sets of vents and spare jets and stuff but not much in the ball park of what I've finally settled on! Bet there's drawers full of the stuff all over the place. Other job for me will be accelerator pumps as they certainly dont perform the same on both sides and that's another learning curve. Did you ever go down the route of looking at auxilliary vent conversions?
