I have triple 45 dcoe's on a crossflow and have used an oxygen sensor and gauge to set them up. This is the only way to do it as there are too many jetting variables to do it any other way.
Alot of the literature on how to tune webers is not very good- they are not economy items but on the same hand, they don't run rich unless poorly jetted. You can run just about any cam and have it run smooth with independent runner manifolds. Also, no mixture distribution inequalities between cylinders.
They can be very sensitive, but with the aid of some jets, emulsion tubes, sensor, gauge, soldering iron and solder can be tuned.
The limitation on chokes is easy to fix- I had my chokes bored out from 40mm to 41.7mm- carbs still operate as intended.
Some points would be:
USE GOOD LINKAGES and use mercury vacuum gauges available from motorcycle stores to set idle vacuum (make sure you get dcoe's with the idle bypass screws ie DCOE 45 152's). Screw all bypass screws in and find the cylinder with the lowest vacuum and then open the other cylinders screws to equalise vacuum between cylinders- it's not hard, just be methodical.
DCOE's on our size engines work well with large venturi's (40-42mm), F7 or 8 emulsion tubes only, 5.00mm aux venturis, idle jet air hole drilled through jet holder like IDA and air hole soldered closed in DCOE idle jet. The centre bore of the idle jet is too big standard and needs to be reduced to about 0.8-1.00mm to prevent richness just off idle. The bigger surface area of the standard idle jet schedules too much fuel in too quickly- less surface area for vacuun to act on- fuel rate of increase needs to be slowed down.
The thinking is that the bigger engines (these carbs were designed primarily for small engines) is that because of the larger engines fuel demand that the progression will carry the engine less up the rev range so that the main circuit will need to come in earlier- that's the idea of the F7 or 8 emulsion tube and the 5mm auxilliary venturi. Figured it out, tried it, and it's the only combination I have found that works well.
With the jets etc, with a soldering iron and solder you can rejet using a Dremel and a range of small sized drills. Once you have the correct size, then go and buy the correct sized jets etc.
Once tuned, they are great and the induction sound is like nothing else around!
