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Carbon build-up on spark plugs???
robnjo - March 8th, 2006 at 08:42 AM

2006...what the hell is going on with me bug???
I have only put two tanks of fuel in to it this year, thats how much I've driven it.
my problem now is massive carbon build up on 1 and 2 plugs,had them replaced just in case they were faulty. its not oil just carbon.we've leaned out the carby to see if that would help, no. its a 1600 with a new solex 34 ,009 and electronic ignition(compufire),this set has been running good all last year so I'm putting it down to fuel, I run PULP.
My Question is this , what should be my plug gap with the compufire? its runs .6mm now but was wondering if i should take it up to .8 or 1mm?
gettin' realy pissed with it....
Rob.


tassupervee - March 8th, 2006 at 09:30 AM

The fact that you have not driven it much is a pointer.
Id take a guess that that particulardriving has also been pretty tame as well?

No, the fuel alone will not carbon up plugs like thatin thats short a time. However, if the mixtures were excessively rich then that would not help. Carboning up plugs used to be a symptom of really crappy fuel waaaay back when but pretty unlikely now.
The cabon issue would most likely be a function of plenty of cold starts and light running below fully warmed up engine temps, extra/excessive oil burning in those cyclinders and just possibly, too cold a heat range of plug, the previously mentioned mixture richness and/or a combination of all or some of them!!!!
There is a cheap and nasty cure for this. Its called the "Italian Tuneup".
Just go out and beat the shit out of the engine with prolonged WOT and maximum revs!! Thatll burn or blow off the carbon!!!!!!!!!! Well, mebbe not, but you get the picture!

Plug gaps are a ticklish one as with an upgraded ignition system, opening the gaps might help with combustion but can be offset by shorter spark duration and in worse case, missfiring caused by either incomplete combustion, crappy leads and/or dodgey dizzie cap and rotor and the associated crossfiring. Kind of taking from Peter to give to Paul

If you are running the pointsless ignition alone then keep your plugs at the stock gap.
If you have added a really high powered electronic coil, high quality leads and the dizzy cap and rotor are in pristine conditionl then you "may" benefit from opening the gap.
NB: you MAY benefit!
Once again, the benefits of a "bigger" spark can be equally offset bu the disadvantages of a shorter duration spark.

In the low tech, low compression and relatively low RPM world of the VW engine, subjective dyno testing has showed little gains to be had by flash ignition systems apart from easier starting, stable tuning and the ability to fire a grunged/oiled up plug that would otherwise most likely missfire!

The rules change once you go right up in revs and C/R tho.
L8tr
E


VWCOOL - March 8th, 2006 at 10:00 AM

Italian tune up...!

Yep, drive it more often and make sure you drive it HARD (WOT, middling to high revs) several times each time you drive it, preferably just before you put it away for its little rest... burns off all the crap


tassupervee - March 8th, 2006 at 03:15 PM

Hehehehehe yer thats what we used to call it when we were apprentices LOL.


robnjo - March 9th, 2006 at 07:15 AM

thanks guys, I'll take it for a fang up to Brissy or something....I guess this is what happens when you miss Dubz by the Pub:(
...so I'll leave the gaps alone and replace some old bits.
Thanks again:!: :beer:beer


VWCOOL - March 9th, 2006 at 08:20 AM

Warm it up a bit quicker by closing your Hoodjax, too