carb jetting

[Beany]

Hi all,
I have a 1970s VW Early Bay, single carb, twin port. I have just done a top end rebuild and changed from 1600 to 16041. It idles well, but I get lots of backfire if I try and drive. I assume the carb needs rejetting, with an increase of the main jet? But I don't know anything about the sizes or numbers. It's a Weber 32/36. I understand these can be difficult? Is there an easier option for a replacement carb? Can anyone help, please?

 

[ozziedog]

Before you get to the jets ,it sounds like you have an air leak somewhere. Try and find it with an aerosol of some description like WD or similar. Usual culprits can be manifold to head, carb to manifold same on zoorst. Watch your fingers!

Ozziedog,,,,,,,,,jets shouldn’t be much of an issue for 50cc

 

[Beany]

Thanks for the response! I will check for leaks!
I found this https://www.aircooled.net/making-weber-progressive-dfev-work-aircooled-vw-engine/
The distributer with the rebuild kit didn't have a vacuum advance, so that'll be my first change to see if it helps. Then I'll look at the heat intake.
Fingers crossed

 

[ozziedog]

How did it run before the rebuild? Was it much the same as this ?
After reading that bit ^^^ from air cooled.net it would seem that a progressive is really a non start unless you’ve got heat intake and vac advance. I didn’t know that you could get a rebuild top end kit with a dizzy in it. I’ve never had anything to do with progressives and after reading that article I’m glad I don’t. But that does make it sound like it can be made to work on the condition that you can supply heat and need an svda to play nicely. It also sounds like it’ll run smoothly (progressively) and fairly economically which is great news all round if it can be acheived but we rarely get to the ‘perfect’ bit. All the ‘issues’ seem to be mainly connected to the huge size of the inlet manifold necessary to feed both sides which requires the intervention of warmth to eliminate / minimise pooling by maintaining suspension. Where twins wins I spose.

Ozziedog,,,,,,,,,,,it is great when they run decent

 

[Beany]

Before the top end rebuild it actually ran very well... All things considering. I never had any problems besides having to re-set the point gaps; no back fire, it pulled well up hills, sat at 65 on a motorway and even the fuel economy surprised my 75 yr old dad. I clocked well over 15K miles the length of the country and through the Welsh hills.

The rebuild was decided upon when a spark plug started popping out. The thread was gone. I could have use a helicoil? But while in there we ran a compression test and found that I was running on about 1 1/2 cylinders!! I don't know how. During the rebuild it was clear that there was a lot of wear and tear and further surprise at how it had even been managing to run at all. The top end rebuild was very necessary.

A quote from the above link may explain the wear and tear:
"Their “charts and guidelines” are horrible. HORRIBLE. It’s almost like they want you to blow up your engine and wear out your rings/pistons from fuel washdown, in 5k miles."

Once it's running again I'll definitely get it on a rolling road and looked at by someone with more real knowledge. If needed I'll switch out the carb for something easier or twins. Can anyone give any recommendations for rolling road carb tuners in the UK? I'm aware of classiccarbs.co.uk. Thanks

 

[Gabs]

Hey Beany, I used JD tuning north Bristol when I put ICT 34 on my bus he did a great job getting everything set up including setting my timing etc.

They only work on classic vehicles through their work.

 

[ozziedog]

Hey Beany, I used JD tuning north Bristol when I put ICT 34 on my bus he did a great job getting everything set up including setting my timing etc.

They only work on classic vehicles through their work.

I’ve never used them myself, but you aren’t the first person to recommend this outfit to me. I’m in Bristol too.

Ozziedog,,,,,,,,,, I use Tog Hill as my rolling road.

 

[ozziedog]

Hey Beany, I used JD tuning north Bristol when I put ICT 34 on my bus he did a great job getting everything set up including setting my timing etc.

They only work on classic vehicles through their work.

I think I recognise that van, it’s way too clean for it to be any good.

Ozziedog,,,,,,,,,,,Zat Chooo Paul ???

 

[sparkywig]

Hey Beany, I used JD tuning north Bristol when I put ICT 34 on my bus he did a great job getting everything set up including setting my timing etc.

They only work on classic vehicles through their work.

John's retired now, I don't know the chap who took over the business.

 

[nickcj]

John's retired now, I don't know the chap who took over the business.

Harry

 

[Gabs]

I think I recognise that van, it’s way too clean for it to be any good.

Ozziedog,,,,,,,,,,,Zat Chooo Paul ???

Hey Ozziedog, it sure is and never got to say see you soon when I left DATC but I heard you got a win with yours. What’s your next adventure as be good to meet up again if your doing a vw festival soon.

 

[Gabs]

Harry

Harry

Harry the son.

 

[ozziedog]

So next weekend I’m at a family camping doo dah down on a farm overlooking Corfe Castle. The next few adventures have got to be Wobbly with the Castle Crew and Techenders up at Lutterworth with the LateBay gang, not sure if I got anything else concrete but I wouldn’t mind the South Gloc thingy.

Ozziedog,,,,,,,, wot you got on ?

 

[Gabs]

So next weekend I’m at a family camping doo dah down on a farm overlooking Corfe Castle. The next few adventures have got to be Wobbly with the Castle Crew and Techenders up at Lutterworth with the LateBay gang, not sure if I got anything else concrete but I wouldn’t mind the South Gloc thingy.

Ozziedog,,,,,,,, wot you got on ?

I have a couple weeks of from the 5th aug so the 7th I’m hoping for a Monday to Friday down in Dorset at bagwell farm for a chilled week and funny I was looking at the Swansea DATC today are you with the early bay lads Ozzie ?

 

[ozziedog]

If everything goes to plan , I should imagine there’ll be a few. Maybe three four five but it’ll be ace anyway. Believe it or not, it’s even more low key and chilled than the Calidicot shin dig. Mostly peeps going on the proviso they can get the time off , it’ll be great.

Ozziedog,,,,,,,get on to it nearer the time.

 

[mike202]

Thanks for the response! I will check for leaks!
I found this https://www.aircooled.net/making-weber-progressive-dfev-work-aircooled-vw-engine/
The distributer with the rebuild kit didn't have a vacuum advance, so that'll be my first change to see if it helps. Then I'll look at the heat intake.
Fingers crossed

I had an old progressive carb on my first engine for 8 years and it was ok. I had an 009 dissy. I rigged up a pipe from the warm air scoop intake up to the air filter on the carb. I think this helped a bit in colder weather.
I also added an electric choke which was really awkward to do as it attached to the front side of the carb next to the fan housing .
Again, I think it helped a bit in colder weather.

 

[Beany]

Update: Found that the primary throttle shaft was wobbly and leaking fuel/air out the side of the carb. Going to see if it's an easy parts fix, or a just a new carb rather than chasing my tail trying to recondition it. To be continued...