So I just put some new NGK DCPR8E's in today & was wondering what the correct gap is.
Manual says .10 to .15 mm & the plugs came out of the box @ .08mm..... should I leave them alone ???
Also, I have one of thse .99 gappers from Harbor Freight..... no wires just a dial that starts @ zero & works it's way up......on that guage my plugs register .8mm...... must be the guage.... old plugs that came out have the same gap as the new ones.
On the plus side I managed to pull the right side plugs off without losing them in the belt covers [laugh]
Workshop/service manual for '06 S2R1k says 0.7 - 0.8mm.
Quote from: Speeddog on February 26, 2009, 03:08:31 PM
Workshop/service manual for '06 S2R1k says 0.7 - 0.8mm.
+1 on the 06' S2R1k, so is '07 S4R.
Thanks guys [thumbsup]
Funny my manual says .10- .15mm in the paragraph & on the pic it shows .7/.8mm....damn Italians [laugh]
At what interval are plug changes reccomended ???
When it comes to spark plug gaps, bigger is better. The larger the spark kernel that is generated by a spark jumping the electrode gap, the more likely and complete the fuel burn will be, and the smoother the engine will run. That is, the larger the spark gap that's exposed to the air/fuel mixture, the easier it is to initiate combustion. This translates directly into improved throttle response. Not more power mind you, better throttle response.
The transition between throttle positions involves a wide range of fuel/air mixtures and the ability to fire these less-than-ideal mixtures with a minumum of misfires is what throttle response is all about.
So, the larger the plug gap you can run (without misfires) the better.
Unfortunately, the greater the plug gap, the higher the voltage requirement to jump the gap. The difficulty lies in that, any added gap creates more strain on the other ignition parts. Coils, for example, may not have enough stored energy to cross the gap, creating a misfire. Old plug wire insulation can break down at the higher voltages required to fire a larger gap.
The stock Ducati coils are good enough to fire a 1.1mm plug gap. Any gap larger than this will likely result in more misfires (there's always a few) and subsequent power loss. The correct new plug gap is specified at about 0.6mm-0.9mm). But, remember, as a plug wears, the gap opens up further.
If you use conventional sparkplugs, start with the recommended gap and try opening the gap up in 0.05mm increments. You should note a progressively smoother throttle response if not more power. When the bike begins to lose power, go back a bit and this will be your optimum gap.
I as a good rule-of-thumb, if you go more than 0.2mm over the out-of-the-box gap you won't maintain parallel surfaces between ground and the center electrodes. So if you reach that point, change to a plug that starts at a larger gap. The NGK dash 9 series starts at a 0.9mm gap, and is used for that reason.
If you run iridium or platinum electrode plugs, start with the 0.9mm gap that they are shipped with. Don't run them at smaller gaps or you'll loose throttle response.
If you have a older bike, you may arc over the plug wires before you can reach the optimum plug gap. If the spark plug wires have inadequate insulation, the wire cannot maintain a high enough voltage across the insulation and will arc to ground before firing the plug gap. The factory spark plug leads are stranded wire covered with an EPDM jacket and although the wire itself will last a long time, the jacket will start to break down after a couple of years which is why most good aftermarket wire is insulated with silicone rubber.
If this is the case, replace the stock spark plug wires with a set of Magnecor or similar quality wires. This will allow running a larger plug gap without a concern for insulating the higher voltage needed to jump the gap.
excellent write up on spark plug gap! thanks.
you should put it over in the Tutorials section.
One thing not mentioned in the piece above. If you run a larger gap, the resulting increase in voltage across the plug electrodes will cause more material transfer between the plug electrodes effectively shortening its life. To avoid the need for all the above and the mentioned pitfalls, just use fine wire plugs (Iridium(best), Platinum etc). The electrodes are thinner/finer which increases the kernel area right out of the box and they use less voltage to fire any given gap. Material transfer in fine wire plugs is next to non-existent. They cost more initially, but last longer and perform better. They really do eliminate the need for over-gapping. Just .05 worth from an ex 20 year mechanic....
Back in the day when moto ignition systems were barely sufficient to fire a plug at all we'd use fine wire plugs, accel coils, and an increased gap.
It definitely made a difference in smoothness at idle and acceleration/throttle response.