VW carb switch, 34 to 30

[ericheath]

Temperature and humidity combine as factors. With 100% humidity you can have icing at 60 degrees.

I’ve been reading the single carb builds as people share them. I haven’t done one, so I can’t say, but I think there are a lot of factors and many variables. I have noticed one thing stood out as seeming to give a higher chance at success, it’s the ones who’ve used a larger plenum (vw type 4 I think) and although it is made for a 2bbl, they add a two-into-one adapter between the carb and vw plenum.

There is one guy who also successfully put on a four barrel sticking up thru the false tank with a roots blower looking scoop on it.

To me, what stands out on those as opposed to the log style is the fuel has a decent drop down before going to each cylinder. I don’t know if that’s a factor in their success or not, just an observation.

Another one that stands out as really different is using just one inch ID pipes for the runners. I have watched videos of it and it sure seems to scoot. Big runners may help at wot, but who rides at wot?

[taunusrainer]

Very interesting icing diagram. If one builds a 4to1 intake manifold, icing will occur unless it is not heated by either engine oil or coolant. When I did tests on homemade manifolds long ago, the icing thing caused me to give up. Later I grabbed a used CC products manifold (coolant heated) and went on. Weber progressive 28/36 DCD was the most successful choice, but never came close to stock carbs. It ran ok, nothing more nothing less. Fuel economy was also an issue. Maybe I never found the right combination of venturis and jetting...

[JohnB1953]

I too have thought about using a PICT30 Solex carb . I have a little experience in that I have a VW trike that I built in 2008. It had a 1600 dual port with a pict 34 carb. It was ok but could be a bit of a pain to tune. This last winter I rebuilt a 1641 single port with a remanufactured PICT 30 carb. What a difference in motors better power much smoother. That got me thinking I bought a light roll over 1981 GL1100 trike and rebuilt it for my son in 2015. The wing had carb issues from sitting and I was able to buy a nice low mileage 1100 for less time and money so I have the old GL left over. I have always thought a single carb would be worth looking into, so I really like this thread. I also found out the hard way that those EMPI and other cheep china carbs are NO GOOD. I have another stock PICT30 I am going to send out to Volksbitz and have it remanufactured . I need to do a little more research on manifold construction.I don't know why this carb wouldn't work as my VW is 1641 cc and around 50 or so hp, and like I said it runs great. So I hope to hang around here and learn. Thanks John B

[ob1quixote]

Had my wing out for a trip to TN to ride done mountain twisties. 26 mpg when spanking it on the slab, 30-32 mpg when running in the 65-70 range. Rock solid 900 rpm idle when fully warm.

[ob1quixote]

Headed for a BRP tour last weekend of the month!

[Randall.Huston]

I've been following your thread and I was wondering how it's performing lately? I did the swap last month but I went with a different style manifold and the 34 Pict 3 carb and so far I'm loving it. I did a couple of things to mine. I swapped out the main jet for a 135 and drilled out the idle jet to .008. It doesn't like cool damp air very much although it does run well after it warms up. I also cut a hole in my fan shroud so the fan blows hot air back onto the carb and manifold. Mileage isn't great at 32 but it's good enough to suit me at least for now.

[Randall.Huston]

manifold.jpg

I have this manifold. I'm switching to this one as soon as it arrives.

X manifold.jpg

[Deseenor]

I have this X manifold and a mid price be 34 pict 3 carb installed.
I had a nightmare journey with the original carbs and couldn't get them run properly.
I changed main jet to 160 on the VW carb.
It runs, not perfect but better then original.
Is there anyone can give a proper setup of jet and idle with these X manifold I would be more then happy.
With ice I have no problems.
I have problems to start the machine, it needs some 10 second to get it run first time. May be the way from carb to cylinder is the reason?
Here's some ideas would be great as well.

[ob1quixote]

My main jet on the 34 and now the 30 is a 127.5
Air correction jet is a 65.

Still have some work to do on the mid jets, been busy and hot around here!
Since I installed electric manifold heat controlled by a thermostat, I can watch the manifold temperature drop after starting the motor, until the electric heat and scavenged heat from the coolant crossover tube catches up.

After a good run, the heat of the motor will boil the fuel in the bowl. At the next start, it takes a bit for the fuel pump to refill the bowl. When I get my jetting done, I will be installing a phenolic insulator between the carb and manifold for a thermal break.

[bbuice]

I am attempting to convert my 75 GL1000 to a single carb. I am using the 34pict. I followed all the pre-install setups and can't get the bike to idle below 2k rpm. I'm wondering if I should give a 30pict a try based on your experience. Were you able to get your 34 to idle? Any ideas why I can't get mine to idle? Any suggestions would be much appreciated. Would you mind listing the final jetting changes you did? Thanks very much.

[ob1quixote]

Just did list my jetting so far! Couple posts up, ended up with the same jetting in the 30 and 34.
I did get the 34 to idle well. All I can suggest is that you only tweak on a full hot running motor, and do it on the center stand.
It was very, very tedious. Like I said in the PM, altitude changes forced me to change it en route.

My Solex 30, I have a rock steady idle at 900-1Krpm, after it warms up.

I think the smaller bore 30 is more compatible with the 1000cc motor's amount of air flow, and the 34 is just too large.

[JohnB1953]

I agree on the pict 30 being a better choice. As most don't realize that the dual post ending that the pict 34 is used on is to work on emissions crap. I have had both and my current vw trike has a 1641 single port with poct 30 and it is 2x the motor the old 1600 dual part ever was. I have an 81 wing I want to put a pict 30 on is I ever get the time.

[bbuice]

Where do you get the replacement jets?

[ob1quixote]

Ebay.
The seller with the most selection is in Italy, but you can find some in the US.

[bbuice]

Ob1quixote, I know one of
The jets is accessed by removing the drain plug but how do you get to the other one? Thanks