Carb over-fueling?? Backfires & splutters

Ask and give advice here
Post Reply
Posts: 1
Joined: Thu Dec 07, 2017 4:40 pm
What model do you have?: 68' 1300 Single Port
Location: Port Elizabeth
Flag: South Africa

Carb over-fueling?? Backfires & splutters

Post by Poenie » Thu Dec 07, 2017 6:09 pm

Hi All,

I have recently bought myself a new toy to play around with and fix up as a pet project. It is a Beach Buggy built on a 68/69 chassis. The original engine looked like it was a 1600 twin port, but this seems to have been changed to a 1300 single port engine, according to info gathered from the internet. It has a Solex H30/31 PICT carb.


Motor seems to struggle a bit to start, but once started, seems to idle ok. Problem is that it splutters and backfires when revving and definitely does not go to full RPM. It also blows out grey "petrol" smoke, so seems to be running extremely rich. Can anyone make a suggestion as to where I can start looking for the problem.

As a point of interest, this is what I have done so far:
I repaired to stripped spark plug threads via Helicoil, as cylinder 1 & 4 was staying cold on the exhaust manifold.
I have replaced the spark plugs and checked for spark on all cylinders. Fly leads are also connected correctly.
I have set the carb to the suggested setting ( 2 and a half turns from on both screws ) I have also played around with this, but not helping.
I have set the points.

I have also set the timing, but I am still trying to figure out whether I have done this correctly. I checked for TDC with piston one being "on point". The pully has two markings on it - a "slit" on the back and a small round/oval marking about 15mm to the left of that, on the front of the pulley. Which one is used as the timing "marker" so to speak. I used the slit in the back, but this could be wrong? I have read about the 7,5 degree advance etc, but I'm still not sure that I got it right. O, and the distributor has the vacuum advance on it, if that will help in anyway to find a possible solution.

Thanks in advance, if anyone can point me in the right direction.

User avatar
Tony Z
Posts: 13750
Joined: Wed Sep 14, 2005 8:33 am
What model do you have?: 2.3L 69; 1302; P/Van
Location: Klipheuwel (near Durbanville), Cape Town or working at sea
Has thanked: 110 times
Been thanked: 312 times
Flag: South Africa

Re: Carb over-fueling?? Backfires & splutters

Post by Tony Z » Thu Dec 07, 2017 7:14 pm

firstly, check for vacuum leaks - there is a sticky on how to do this in the advice section.
Then rethink your helicoil spark plug thread repair as you need to use a solid insert, not a helicoil

The timing: the dent is 0deg or TDC.
Remove the vacuum tube from the dizzy and set idle timing with a timing light to the V slot, at 900 to 1000rpm.

Do a full service and set your point gap prior to setting timing and make sure your valves are adjusted properly.

User avatar
Posts: 6519
Joined: Mon Feb 07, 2011 8:51 pm
What model do you have?: 52T1,68FB,72Bay,75FL
Location: Eich! no, in Port Elizabeth
Has thanked: 92 times
Been thanked: 309 times
Flag: Netherlands

Re: Carb over-fueling?? Backfires & splutters

Post by retrovan » Thu Dec 07, 2017 7:52 pm

Aas Tony said,...

As well as have a look at your float level, as it may not be closing and you then get fuel flowing into the pistons.

Fuel smoke is normally not timing, but too much fuel.

Are you using an electric pump, if so is it a low pressure pump below 3psi.

1952 Split Beetle 1835cc twin 34ICT's (Azure Blue)
1968 Fastback (2Lt.type4)twin 34ICT's( Red)
1972 Low Light Bay Panel Van (2Lt type 4)twin 34ICT's(White)
1975 Fleetline Panel Van 1914cc twin 34ICT's(Aqua Blue/White)

User avatar
Cyndi Kritzinger
Posts: 1033
Joined: Wed Apr 24, 2013 3:49 pm
What model do you have?: '76 BRAZILIA '78 BAY
Facebook: yes
Location: DURBAN
Been thanked: 38 times
Flag: South Africa

Re: Carb over-fueling?? Backfires & splutters

Post by Cyndi Kritzinger » Mon Dec 11, 2017 8:52 pm


Terry Phillips
Single Port
Posts: 1246
Joined: Mon Jul 16, 2012 5:56 pm
What model do you have?: T3,58,60,61beetle
Location: Kempton Park
Has thanked: 30 times
Been thanked: 70 times
Flag: South Africa

Re: Carb over-fueling?? Backfires & splutters

Post by Terry Phillips » Mon Dec 11, 2017 9:20 pm

White smoke unburnt fuel
Black smoke is air or lack of it.
Blue smoke is oil.

Post Reply