Ducati Sporting Club UK > Model Specific - Discussion, Technical Problems and Help > Sport Touring: ST4 / ST3 / ST2 > St4s spark plugs question

[PeteC]

This might be a silly question,but here goes....

Done the cam-belts today, but my spark plugs are a little worse for wear,
anyone have a recommendation for a slightly 'hotter' grade plug than the standard 'Champion RA59GC' ?


Judging by the colour of the plugs that came out, my engine is running on the 'cool' side (black and sooty).

Pete

[rockhopper]

Wouldnt it be better to stick to the correct plugs and get the reason for them being the wrong colour sorted out? Probably only needs setting. Nelly at Cornerspeed did a superb job on my ST4 and who knows, if you get there this week he might even have some real milk left!

[nelly]

I've never "got on" with Champion plugs. I prefer to use NGK. The plug you need is a DCPR9E or alternatively the DCPR9EVX.
Paul's right in that the plug is probably fine and you'll benefit more from having the injection set up correctly.

Oh and all the milk has gone.......:P

[PeteC]

I think NGK plugs tend to run 'hotter' than the equivalent 'Champion' ones anyway,
based on previous experience with other
(older) bikes. (I'm a former 'Jota' owner)

Although I don't see why the injection should need tweeking, once the idle co has been set?

Pete

[nelly]

The injection system relies on more than the idle CO to run correctly.
The throttle position sensor is the real key to having it all running correctly.
If the idle CO is adjusted to "compensate" for the TPS being set incorrectly then it'll still fuel incorrectly at anything other than "closed" throttle.
The throttle balance also affects running, and again, is possible to mask this by adjusting the air bleed screws to compenste the CO across both the cylinders.
Is one plug sooted more than the other? The rear cylinder will usually run richer if the set up is out.

[PeteC]

No real appreciable difference,if anything, front one was slightly 'sootier' (is that a right word )

Looks like I'll have to plan a visit to a workshop somewhere, trouble is the 'St' is my only form of transport, (don't have a car).

Pete