Carb over-fueling?? Backfires & splutters

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Poenie
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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.

NOW WHAT???

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.



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Tony Z
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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.

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retrovan
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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.

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Cyndi Kritzinger
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Re: Carb over-fueling?? Backfires & splutters

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

I MAY BE WRONG BUT I THINK THE GREY SMOKE IS OIL AND BLACK SMOKE IS FUEL????

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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.

Poenie
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Re: Carb over-fueling?? Backfires & splutters

Post by Poenie » Fri Jan 05, 2018 11:03 am

Hi All,

Many thanks for the advise so far. Sorry, have been on holiday for a bit, but will be starting up again in the next week or so. Will then check all of the above and will keep everyone updated as to whether the problem gets sorted or not.

Hope you all have a great 2018 ahead of you.

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Re: Carb over-fueling?? Backfires & splutters

Post by slak » Fri Jan 05, 2018 11:14 am

Also check for dirt in the idle jet " on the right side of the carb no.8 spanner" should be 2 check both
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fig
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Re: Carb over-fueling?? Backfires & splutters

Post by fig » Tue Jan 09, 2018 4:20 pm

Your symptoms could also be caused by a faulty condensor. Best to ensure everything is perfect with the ignition and timing before you start messing with the carb.

The carb settings only adjust the idle speed and mixture, and shouldn't really cause the symptoms you describe unless there's a float level or puncture problem. You should do the idle adjustment only after the engine is running right.
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