Dual Weber Conversion conversation

[earthquake]

I will go ahead and add some pics anyways...
The "sync" valves are next to the A/F screws [you just crack them open like a brake bleeder] and the Idle jets holders are the brass screws in front of and to the left and right of the jet stacks, on my other IDF's the idle jets are on the side. They also have no "idle air adjuster screws" you can adjust, they are plugged with a aluminum plug. [should not be to hard to get out]

[gregforesi]

Those are a bit different. They have the long-nose secondary venturi's. Those aren't available (aftermarket) for an IDF.

I had to open the idle air adjustor on my #1 cylinder. The other carb was correct with the adjustor's closed. At any rate you may need the idle air adjustors to sync one throat to another on a single carb. I'd wait and see. Maybe you won't need them.
The vacuum ports can be plugged. I used the sync tool that I purchased from Pierce Manifolds. It's the fan type and works fine and is really easy to use on the velocity stacks.

I agree that those carbs were probably "specials" created for the Alfa 1300. That makes them a pretty good choice for a Wing motor. Pull an idle jet and see if it is the same as a regular IDF. If they aren't you'll be soldering and re-drilling to change the idle jetting.

My backfire problem:
I've mentioned this before. The motor runs like a pup. It idles perfect and winds up perfect when the throttle is blasted open or slowly rolled on. No issues there. when backing down from high RPM there was no popping or backfire out the exhaust. Under steady state throttle at 3500 to 4000 RPM it randomly spit through any of the 4 carb throats and backfired up the throat. I ran the numbers on air velocity through the throats at different RPM. Thinking that I didn't have enough air velocity to properly pick up the fuel I went to 26mm Dell-Orto main chokes. The problem was lessened but didn't go away. The 28mm chokes provide a flow rate of about 215 CFM per carb. I haven't come across any numbers for 26mm chokes but I think I've cut it down to about 195. That's 390CFM (down from 430) on a motor that displaces about 155 CFM at redline. Close enough.

Last weekend I finally got around to Dyna coils and wires and opened the spark plug gap to .034". Exhaust note was immediately different even at idle. Deeper. I can tell it's burning more efficiently. On the first test ride the backfire was less but still there about once every 4 or 5 miles. Annoying. I had never changed the idle jets once I had it running well. Looking back at my air velocity numbers I realized that the cross-over from idle circuit to mains was being delayed by the slow air velocity of the small wing motor. The 25-2800 RPM cross-over numbers that I had come across on many websites (and that I was relying on for jetting) were not true for the GL1000. The cross-over is much closer to 4000 RPM.
I went from 47 to 50 idle jets and there was a big improvement. I am currently running 52 idle jets and the problem appears to have gone away. So my current theory is that it was truly running lean but NOT because of the mains/air correctors (where I had focused so much attention). The idle jets were too small and it was running out of fuel before it started sucking on the main jets.

It still isn't taking any trips to California but when I have to run along at 65-80 MPH on the freeway it does it without griping anymore.
It only took me a year and 6000 miles to figure it out but now I can honestly say ... "It isn't running too good but yea, I'll race ya."

[macka]

Just spit balling here, but what about using geo metro tbi and a microsquirt on the dual carb kit?

[gregforesi]

I took a look at the Jenvey throttle bodies that are a direct replacement for Weber 40 IDF's. They are pricey. The outboard mounting of either the Webers or a Jenvey FI system just has such a mechanical (maniacal?) look to it that I'm kinda hooked. So if I was going to go FI I would put Jenvey's on Randakk manifolds and control them with the micro-squirt. I figure it would end up near $2000 to get it done correctly.

[randakk]

I took a look at the Jenvey throttle bodies that are a direct replacement for Weber 40 IDF's. They are pricey. The outboard mounting of either the Webers or a Jenvey FI system just has such a mechanical (maniacal?) look to it that I'm kinda hooked. So if I was going to go FI I would put Jenvey's on Randakk manifolds and control them with the micro-squirt. I figure it would end up near $2000 to get it done correctly.

If I ever do FI, that's exactly how I would do it. I don't think any other approach (normal aspiration) could top that setup.

[macka]

yea but you can get the metro throttlebody for under a hundred and it looks kinda ratty

[drum4fun76]

I'm glad to know that someone will be explaining this conversion. I've just posted questions in the tech discussion forum about this (did not know about "unique carburations" section). I'd love to work on the same set up this winter, but they don't give away those carbs... man!
Anyways, good luck and keep us posted!!

[gregforesi]

I'm running them and they run very well. I don't think the cams are a big thing but I am running '77 cams in my '78 motor (the bike came with a low mileage extra '77 engine that is my donor). I never ran the bike with the '78 cams. The Webers are racing carbs and can be touchy about the weather and there is no "cold weather enrichment" type of choke so the bike is cold blooded. Once the engine warms up it's fine.

This is not a straightforward-everything-is-in-the-box conversion. Randakk took great pains to develop the system and instructions but about the only physical thing you get is the manifolds and maybe a pair of Randakk grips. Not an issue if you have access to some shop tools (bandsaw and drill press come in handy). The instructions are pretty good and the suppliers for the different parts you'll need are listed as well. I've currently got around 7,000 miles on my setup. For me it was the whole point in building a GL1000 cafe racer/street fighter. Would I do it again? In a heartbeat.

There are cheaper ways around the carb price issue. Empi makes a model that is a copy of the IDF. I've heard that the early Empi's should be avoided because of porosity in the casting. The newer ones are supposedly better.
There are used carbs available here and there. Used carbs will need a rebuild and will likely require re-jetting and maybe different size carb throats (called chokes in the Weber) depending on what is in them when you get them. I budgeted for the Weber conversion and went with new carbs. I've got around $1200 into the setup (counting the electric fuel pump). If you go with used carbs you may save some cash up front but you'll lose some of the savings getting the carbs fixed up for the bike. The linkage pieces, rain hats (or v-stacks) and air filters, etc. start to add up.

The conversion isn't difficult but it isn't what I'd call a piece-of-cake. There is some head scratching involved. If you go with the rain hats (as Randakk suggests) you can avoid having to scallop the shelter doors like I did. On the other hand - people notice those 4" velocity stacks and invariably comment on the scallops.
I had the motor out of the bike when I was working on the intakes and linkages. That made it way easier to repeatedly put things on and take them off.
There is a current thread ("Help Me") started by a fella in southern Ohio who is struggling to get his bike to run with the Webers. These carbs are very touchy about vacuum leaks. Used carbs may need the throttle shaft seals rebuilt. New or used - even a pinhole leak will have you chasing your tail on the carb tuning.

The other thing about Webers is that they sound freakin' awesome. The Weber conversion gives the bike a certain "mechanical" look (maniacal?) that is missing from modern motorcycles. People notice them right away.

The other thing about me is that I'm a terminal show-off. Every time I look at my 1000 I start grinning. It was a perfectly good bike when I started out.

Here it is at the Battle of the Brits as the "Trash Bagger". So realistic that you can almost here the rear wheel clicking.

[earthquake]

I posted this over on the "HELP ME" thread but I will post it here too as it relates to the thread, This is from a gentleman named Mark Harney, he is one of the gurus on a VW forum I'm on a lot...
http://www.carburetorclinic.com/index.htm
This is a good read about Weber IDF's and some others.

Casey

[vwfye]

if you are having jetting/synching issues, i can help there. i deal with these carbs daily on VWs. jetting is most always based on venturi size, not engine size. it is all about the air/fuel ratio based on the signal the carbs get from the air flow rate.