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Author: Subject:  1200 Beetle / buggy fouling plugs
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posted on January 24th, 2020 at 07:26 PM
1200 Beetle / buggy fouling plugs


Hi Everyone,

I'm new to this forum but not new to air cooled VW's. I'm having ongoing trouble with a '64 1200 engine that's on a farm buggy I've owned since 1984...

It's had an ongoing problem with fouling plugs with soot in recent years, as if it is running rich.

Here's a bit of history:
- Engine was rebuilt for a road car in 1990
- Transplanted into the buggy around 2000
- has an stainless extractor and muffler (used to have straight though buggy hotdogs, but they fell apart) so it should have normal back pressure.
- Has had hot spark electronic ignition fitted and has advance tuned by trial and error for best idle and power.
- runs unleaded (used to use lead replacement additive but thought this might have been the problem)
- The problem seems to be worse when my mother uses it for an extended period, she just putts around the paddocks at the farm. It gets better when my children drive it for a weekend and give it a flogging.
- I've tried hotter plugs and different coils
- usually when I go up for a weekend it's running on 2 or 3 cylinders, I remove the offending plug(s), clean with carb cleaner, then all is well.
- I have tried different carbs, I can't remember which model is currently fitted, Solex 28 PICT most likely.
- Choke isn't running closed
- Exhaust is clear unless throttle is snapped open and accelerator pump gives a shot of fuel, then it gives a puff of black
- I'm currently trying running idle mix super lean (about 3/4 turn at the moment)

Is there anything else that could be the issue? Anything I'm missing?

Thanks in advance,

Tony.

PS: Recently had an issue with worn flywheel ring gear, turned it 90degrees on the shaft, it worked an absolute treat!
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posted on January 26th, 2020 at 06:30 AM



Well if no one else wants to help you out, guess it's down to me
.... Try moving around the offending spark plugs / spark plug leads around to other cylinders to see if fouling stays with certain cylinders
try also to adjust your valve lash .006''
also try a compression test as this would indicate bad rings / valves / pistons
look closely as distributor cap / rotor for tracking of arc
check manifold seal rings at head
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posted on January 26th, 2020 at 06:56 AM



Also check your air cleaner is not clogged up as this will cause a rich intake mixture
overly retarded timing can also be a problem
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posted on January 26th, 2020 at 06:59 AM



too thin oil is another problem
check fuel pump diaphram is not leaking fuel in the engine making oil thin ....oil will smell of fuel
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posted on January 26th, 2020 at 07:15 AM



But ....first thing to look at is the type of fouling on the plug
black sooty dry ....to much fuel fouling
black wet with deposits ....oil fouling

Also check plug gap is correct
check plug for arc tracking on the ceramic
check plug holder and air seal for arc tracking as this will still cause a new plug to stop sparking also
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posted on January 26th, 2020 at 07:17 AM



Anyho.... just a few things off the top of my head that may help you out
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posted on January 26th, 2020 at 07:24 AM



"Exhaust is clear unless throttle is snapped open and accelerator pump gives a shot of fuel, then it gives a puff of black"

Check that the engine has not swallowed the accelerator pump brass discharge jet as it's only pressed into a taper in the carb
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posted on January 26th, 2020 at 07:28 AM



check valve guides also when setting valve lash as have had them come loose as they are only pressed into the heads
if loose that can cause oil to flood in and foul a plug
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posted on January 26th, 2020 at 07:38 AM



too much fuel pressure and your bleeding fuel/overflowing the bowl
stuck needle valve, bad float
check crank case vent is not clogged
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posted on January 26th, 2020 at 07:12 PM



Thanks Yasdnil01,

It's dry sooty, I definitely think its a combustion issue and not oil burning. Exhaust is the same, no signs of oil in exhaust system or smoke. There's also not pattern to which is the offending cylinder, it's totally random which one fails first. Clean of the inside of the plug always rectifies, which is why I've tended to look away from ignition system issues.

I'm thinking maybe I've overlooked something really simple that you have suggested, the air cleaner hasn't had any attention for a long time. It's the old oil bath type, I might give it a real birthday next time I'm at the farm.

I also haven't checked valve clearance for a while, so I'm thinking that might also be a good bit of maintenance to catch up on.

Thanks again :starhit:
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posted on February 2nd, 2020 at 06:22 AM



ok not a problem
keep us posted on the outcome


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