XFlow Sooty Spark Plug

[virden]

 

Is this the beginning of a problem? If so where do I look?

 

Just did 250 faultless miles yesterday, no.1 plug is very sooty, the rest are text book perfect- brown and clean, the Exhaust pipe is also very sooty. The inside of the K&n filters were spotless, but there was some oily residue on outside plates facing the carbs. Only other thing of note is that when on constant revs above 2500 I get a sound (putt, putt, putt) from the carb side similar to that of an exhaust gasket failure at the head/manifold joint.

 

1996, 1700 Super sprint, 20,000 miles, 40's with K&N filters, all standard spec except for a 4:1 exhaust. Fuel consumption is about 27mpg when sensible, uses about 200cc of oil per 1000 miles. Does not fluff or bang on over run.

 

 

[virden]

Is this the beginning of a problem? If so where do I look?

 

Just did 250 faultless miles yesterday, no.1 plug is very sooty, the rest are text book perfect- brown and clean, the Exhaust pipe is also very sooty. The inside of the K&n filters were spotless, but there was some oily residue on outside plates facing the carbs. Only other thing of note is that when on constant revs above 2500 I get a sound (putt, putt, putt) from the carb side similar to that of an exhaust gasket failure at the head/manifold joint.

 

1996, 1700 Super sprint, 20,000 miles, 40's with K&N filters, all standard spec except for a 4:1 exhaust. Fuel consumption is about 27mpg when sensible, uses about 200cc of oil per 1000 miles. Does not fluff or bang on over run.

 

Edit: Have just fired her up without the filters on. Noted that the trumpets are rotating on the rear carb, but nuts tight. Raw fuel as collecting on the filter back plates and dripping down from both carbs 😳 😳?

[john g]

IIRC undo the nut retighten the set screw carefully to hold the trumpet and retighten the nut. A little sealant around the nut may not go amiss.

[OliverSedlacek]

Just like my problem?

[Roger King]

Rotating trumpets are a nuisance, but don't really cause any problems (unless the fixing studs or nuts are loose of course).

 

Sooty plug might be nothing more than running rich on the idle screw setting for that cylinder, but at 20,000 miles a standard spec Supersprint is coming into the area where the piston rings can give up the ghost. This is not a criticism of the rings, but of the application they are being put to. They were never designed for the sort of compression ratio or revs they have to deal with and therefore are prone to failure or even breakage.

 

This does not mean that you actually do have a problem, but it is something to look at if no other cause is found. Any drop in ring performance is likely to lead to less than perfect combustion, which in turn can lead to dirty plugs.

[virden]

Have sorted the rotating trumpets (no.s 3&4), by tightening the locking screws. curiouslu both were blackened as if by fire. Is it possible the noise I am hearing is a back fire ito the carb? I shall check the tappets to ensure all gaps are correct, and then I guess a compression test for the rings?

[virden]

I fixed the rotating trumpets (No.s 3&4) by tightening the locking screws. Curiously both wee covered in light grey soot. Is it possible the noise I am hearing is a misfire through the carb? I shall check the tappet gaps. A compression test will tell me the state of the rings?