smokey plugs

[John Mellor]

Hi folks, all 4   plugs quickly become carbonised. Known this for a while but ignored it as it seemed to be running so well.However just bought a gunson colour tune and surprise surprise colour is yellow; couldn't seem to adjust jets to give a blue colour. Lifting piston slightly caused engine misfire within a few secs. Balance as judged by ear seems ok, starts well not smokey exhaust although tail pipe is black. Needle problem???

Regards all

[RobH]

Obviously the car is running rich and you ought to be able to adjust that by screwing up the jet adjusting nuts. If that doesn't work then possibly the jet or needles are worn or perhaps the fuel level is too high in the jets?  

The other possibility is that the needles are mounted too far into the carb pistons. The shoulder on the needle should be flush with the base of the piston but it is possible to mount them further up.  

[keith1948]

Hi John

What carbs do you have? I had an issue with Strombergs a few months ago now where the ethanol in E5 petrol was causing the floats to 'blister'. Changed them for the 'stay up' ethanol resistant ones from Burlen. I checked the float height as well. If it is SU's then I don't think those floats are as susceptible although again you can get a 'stay up' type.

The other thing to look at would be the air filters. I have K&N filters on my 4A. They need washing out and re-oiling at intervals.

On Strombergs check for splits in diaphragms.

What plugs do you have fitted?

Keith

[RogerH]

Hi John,

 the blackening could be  caused by engine oil due to ''blow by''

Carb adjustment doesn't help.  You could try a hotter plug.

On the SU does the choke assembly return to the off position.? 

If you have blocked/dirty K&N do NOT wash then in petrol   they will shrink.

 

Roger

Edited April 29, 2023 by RogerH

[keith1948]

Hi Roger

K&N do a special cleaning spray and re-oiling fluid. I won't ask how you discovered that petrol shrinks the filters!

Just a thought on oil getting onto plugs, I once fitted the extra oil feed to the rocker shaft. The amount of oil it delivered was too much and I think it was going down the valve stems and I had to remove it because the plugs were getting oiled.

Keith

[RogerH]

Hi Keith 

Jeff at Moss told me about not using petrol to clean the K&N filters.

 

Roger

[John Mellor]

Hi all, jets adjusted up to stop, just about seeing blue in front two cylinders. Oil change at 1 year and 1500 miles showed surprisingly black oil - don't know if that would be normal. 

Having said that it starts a dream, crisp response to throttle opening, pulls like a steam train and has a lovely regular exhaust beat

Choke does close properly. Can't remember what plugs are in ( I'm away at the moment) .

[Ade-TR4]

Hi John

 

I assume timing etc is spot on? Worth double-checking before adjusting the carbs?

Rolling road sesh?

BWs

Adey

[John Mellor]

Hi Ade, Pertronic ignition and set up by Neil Revingtons guys less than 1000 miles ago so all good

[Lebro]

If engine setup by Revingtons, then something must have happened since I would think.

I would check Carb pistons sticking,   Float chambers overfilling, Choke not closing completely.

Or it may just be short runs with choke, & not enough time with no choke to change the colour back to being "correct"

Bob

[John Mellor]

Hi Bob, coming round to thinking it's float chamber level too high. Ordered new levers from moss, the old ones are somewhat battered