Twin carb conversion...a proposed cheaper way..

[trevor42]

Be careful when comparing carb sizes not to get stuck on cumulative bore diameter. Especially if you're looking to replace a multi carb setup with a single or progressive.
The important number on a carb isn't the diameter of the bore but the area. A 31mm bore will have an area of around 755 sq mm. Compare that to a bore of 36 mm with an area of about 1015 sq mm. My concern would be winding up over bore when the secondaries are cracked open. Quad 31s would net a little over 3000 sq mm of bore area, as opposed to the proposed 28/36 which would net about 3230. You could end up with the air running too slow through the venturies.

[trevor42]

Of course if you're running open pipes and/or larger dia bores already, my above point may be moot.

[gregh35]

You could end up with the air running too slow through the venturies.

The key point above in these carburetors (single carburetor applications) is choke size.

32/36 DGV= cast-in chokes cannot be removed or replaced. They're intergal to the carb body.
28/36 DCD= removable chokes can be sized to displacement allowing for proper tuning.

The 26/27mm chokes in a DGV are too large for a 1000/1100cc engine. Weber does not recommend a carburetor with bore openings and chokes that large for such a small displacement engine. Carburetors have particular airflow requirements.

22 or 23mm primary chokes would be more suitable for a 1000/1100 when using a DCD.

Tune the secondary for however you ride. A 23mm secondary choke will give great economy and good performance with a linear transition. A 27mm will give poor economy and superb performance with a two-stroke kind of powerband hit when it comes on. Go too large of a secondary choke (ie. the 27mm) and you will have transitional problems that will be hard to overcome without some serious tuning patience, lots of trial and error and you'll sacrafice drivability no matter what.

Personally, I like a smooth and seamless transition from primary to secondary. Completely linear. That's what I like.

[fish]

BTW
G35 is referring to he venturis when he says "chokes"

[gregh35]

I'm really just pointing out that the DGV style of fixed-choke carb (current 32/36's in particular) are not the best choice in a single carb app. They seem to be the most popular when it comes to someone wanting to give a conversion a try.

[earthquake]

I have worked on VW's for years and have seen just about every kind of carb on them, A 32/36 DGV will work very well on a GW but just like a VW you have to have good manifold heat. on a bug you use exhaust on a wing you would use water, with out heat you will never get a DGV or any other single barrel carb to work well. IDF's will work fine on a wing with enough tuning, it may be a bit soggy off idle but it will wake up quick enough to scare you. I have a friend that is running a set of 48mm IDA [racing carbs] on a 1500 cc motor making 195hp, they have just started running IDA's on 36hp VW motors at Bonneville in the "36hp Challenge"
the 36hp motor is a 1190cc motor that came stock in VW bugs and buses from 1953-60.
I think the best set of carbs you could use on a wing would be a set of 36mm Dellortos which are the similar to a set of IDF's but easier to tune, they will bolt on any manifold a IDF fits. The big problem with dells is they are no longer in production and parts are getting hard to get for them, Weber IDF's are still being made but they are not as good as they used to be [look for Italian made one first then Spanish next] EMPI is making IDF's now and they are getting better then when they first started, EMPI is a manufacturer of HP parts for VW's and most of there stuff is made in china now including there carbs [they are called HPMX's], I allways hear how expensive Webers are, I just bought a set of IDF's for $50.00 off of Craigslist so deals are out there, I have never paid more then $300.00 for a set of used IDF's. Another Weber carb you can try is a set of single barrel ITC's [1 carb over each head] they may have a slight missfire at idle if you do not run a cross over tube to balance the intake pluses, it happens on a VW. there a video on youtube of a guy that runs ICT's on a wing, I will try to find it and post it.

Casey
Here's a picture of my wall of shame, I have a problem. I buy Webers when I see them for sale.

[earthquake]

Here's the wing with the Weber ICT's on it...
http://www.youtube.com/watch?v=kkkikZzUGvM

Casey

[gregh35]

A 32/36 DGV will work very well on a GW but just like a VW you have to have good manifold heat.

Casey
Here's a picture of my wall of shame, I have a problem. I buy Webers when I see them for sale.

Hi Casey - ...compared to what other carburetor?
My manifold is heated very nicely and found the DGV 32/36 5A primary venturi's choke/bore opening combination of 26mm/32mm to be too large to give me a consistant idle no matter how the idle circuit was jetted or tuned. Maybe I'm picky but I did find the best jetting for the application and the bike ran well enough to get the job done.
My primary solution was to use a smaller primary venturi carburetor with a smaller choke/bore opening because the DGV uses a "fixed" choke cast into the body, ...giving me a "...and that's that" solution.

I concluded (along with the Weber set-up information, tuning models and jet calculators in their books) that a 1000cc engine does not provide enough air speed through the venturi to properly activate the idle cicuitry or atomize the fuel when using the 26mm choked section combined with the 32mm bore openeing of a Weber 32/36DGV primary venturi.

I use a smaller progressive Weber carburetor. The 32/36 was not the ideal choice for my engine despite its popularity/visibility on these GL single-carb forums and elsewhere.

Keep in mind that some very powerful, highly tuned GL1000's run single Weber carburetors ...much smaller than the 32/36 for the exact reasoning above.

I believe Octane would be first on the "very powerful, highly tuned" list with a Weber 26/34 (which looks to be a Fiat's DHSA (vacume secondary) and assuming he still runs that particular carb).

PS- I experimented heavily with the variables (auxillary venturi/choke size/throttle plate/jetting/tuning) of the Weber 28/36DCD on my 1000 and found far superior results compared to the 32/36DGV in the end.

[earthquake]

gregh35
Did you try plugging the secondary Idle jet so that it was only idling off of the primary?
This can be a problem when tring to use a progressive on a small cc VW motor or a 2 barrel on a open plenum manifold. I ran a 32/36 on a 76 Honda Civic with a 1200 motor that would idle like it had fuel injection and would rev to 7500 rpm in 1st through 3rd gear, it was a auto cross car. [funny how about half the motor parts worked from a Goldwing worked in a 1200 Civic motor, we had 1mm overbore GL1000 pistons in it, GL valve springs and the timing belt and I think the rocker arms would have worked] I have seen a few Solex 34 PICT's on gold wing, its a good good carb if the bushing are in good shape, chasing air leaks can be a pain.
Here is a chart of most common carbs used on VW motors, hope it helps
http://www.thesamba.com/vw/forum/viewto ... =cfm+chart

Casey

[gregh35]

gregh35
Did you try plugging the secondary Idle jet so that it was only idling off of the primary?
Casey

No, I did not try shutting the secondary down as I did not want to modify the carburetor in any way.

I found it more interesting and enjoyable to rework the DCD for the engine. A highly tuneable carburetor unlike a DGV. Jump into any of the Weber Carburetor books using their charting and none of the calculations put a 32/36 progressive even close to a 1000cc engine. Did I believe it up front? No. I had to go out and buy a new 32/36 (and the various jetting) just to find out that the books were right.
So, I started concentrating my time on something that would work - the 28/36 DCD - and went by the book with it.
The DCD led me to the carb I run now.

Bought my first H-30/31 off The Samba. Lots of great info on that site and some great deals in their *for sale* section.
A PICT34 is too large for a 1000. I tried one of those as well.

As a note - I believe LD is selling his set-up again, and offering PICT 28's and 30's for it.

[earthquake]

I have a 28PCI I built for a friends 36hp motor in his 55bug he was going to run at Bonneville and never did, it would be fun to try it on a GW. It has a 24.5mm venturi [stock is 21mm] that a guy here in town makes and I cleaned up the top plate to smooth out the flow. It needs a float bowl vent and to have the butterfly shaft profiled to increse the flow.

Casey

[radwing]

Hey guys i'm zach and new to the forum. I own a 76 gl1000 cafe racer that I built last year. I'm trying to make it as fast as possible. Does anyone know if it is possible to to put gl1000 heads on a gl1200 block and if it will fit in my gl1000 frame. My goal is to increase the compression by using the 1000s heads. Any feedback would be great

[robin1731]

Hey guys i'm zach and new to the forum. I own a 76 gl1000 cafe racer that I built last year. I'm trying to make it as fast as possible. Does anyone know if it is possible to to put gl1000 heads on a gl1200 block and if it will fit in my gl1000 frame. My goal is to increase the compression by using the 1000s heads. Any feedback would be great

First, welcome to the forum. This question might go better in the tech section. There are some threads that do pertain to that actual mod. But yes to both questions.

We do like to see new people introduce themselves in the welcome and intro section too.

[ericheath]

There's mixed reports on the compression being raised. Some feel it is actually a slight compression drop. It's a doable mod and keeping the 1000 rearend will make it quicker. Lots of options, which carbs, which ignition, etc. The frame may need a little relief in one spot for the 1200 to fit. I would go for an 85 or newer motor. The most detailed build of it is a long one from superskypilot at the stevesaunders site. It's titled Bgirl. You have to cut valve reliefs in the pistons. He shaved the heads a bit to get the compression back. Joedrum has a running 77 with a 1200, 1000 heads and 1100 carbs. He has some posts here, but much more at classicwings.com. I have a little bit in a post here called ngw made me do it. I took 0.025 off the 1000 heads. Warm weather and I hope to find out if it was too much or not. The big gain over just a complete 1200 swap should be the much higher lift of the cams combined with bigger diameter valves. Nobody has, to my knowledge, done a dyno or timed it to see if it actually does improve. Seat-of-the pants reports are that it does. Just the displacement and the higher geared rear end should do that by itself.