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Spark Plug Gap

Larry Vance said:
Is anyone using a bigger gap than factory spec .06-.07 If so, what are the results. Thanks
Click to expand...

Not a good idea. Gap actually increases as miles accumulate and electrodes wear away. Increasing the gap requires more voltage to jump the gap. That can adversely impact coils. I've always set plug gap to the tight side so that they stay in range longer.
 
john zibell said:
Not a good idea. Gap actually increases as miles accumulate and electrodes wear away. Increasing the gap requires more voltage to jump the gap. That can adversely impact coils. I've always set plug gap to the tight side so that they stay in range longer.
Click to expand...
I've always considered this to be correct. Another thing to enhance your spark is to have sharp corners on the electrodes, like they are when new. Once upon a time we used to file and gap plugs to keep the spark hot. If you use Iridium or Platinum plugs you'll notice that the electrodes are much smaller, hence, even when they wear they remain sharper. However, iridium/platinum plugs hardly wear at all anyway. As a rule, you'll get noticeably better performance with them, and for a lot, lot longer - minimum 100,000Km. I haven't used conventional plugs for >20 years and I sure don't miss buying them, gapping them and changing them every 10,000Km or more. First plug change, in with iridiums.
 
john zibell said:
Not a good idea. Gap actually increases as miles accumulate and electrodes wear away. Increasing the gap requires more voltage to jump the gap. That can adversely impact coils. I've always set plug gap to the tight side so that they stay in range longer.
Click to expand...
Hi, it's me again...How can I find the spark plug gap for my California Stone?
 
Georgianna DeGregoria said:
Hi, it's me again...How can I find the spark plug gap for my California Stone?
Click to expand...

Read the manual. If you don't have one the gap should be 0.7mm or 0.027 inch, Since we don't have metric feeler gauges in the US, I set with a round wire gauge to 0.025 inch. BTW, this question should have been asked in the Tonti and Loop section.
 
john zibell said:
Read the manual. If you don't have one the gap should be 0.7mm or 0.027 inch, Since we don't have metric feeler gauges in the US, I set with a round wire gauge to 0.025 inch. BTW, this question should have been asked in the Tonti and Loop section.
Click to expand...
Thanks John, I've been looking for a "Manual" but can't find one and the resource link under downloads does not have one for my bike...ugh...is there another place to find one? I would like to have one by my side, thanks again!
 
V7 III manual says .9mm. Is that something one would stick to or is it better to close the gap. Mind you, mine as an 820.
 
The V7ii manual gives the plugs as NGK CPR8EB-9. The "-9" means they come out of the box at 0.9mm gap. The manual says gap should be between 0.6mm and 0.7mm. Which means they need adjusting from new. Many garages will fit them out of the box without re-gapping, which is wrong - it needs more volts as stated above, and can result in missing sparks particularly as higher revs. I re-gap the plugs with metric spark plug gap wires to 0.7mm, by go/no-go, the 0.65 passes, the 0.70 sticks, with the electrode faces parallel (which cannot be done with flat feeler gauges). I have experimented - gap of 0.5mm misfires all over the place, bike is unridable - gap of 0.9mm misses sparks like the battery is dead. Metric gauges are available; the rest of the world is all-metric and are thoroughly pained by trying to use the inch. Italy has never used that inch, you will find conversion errors in their literature.
 
Louisv97 said:
V7 III manual says .9mm. Is that something one would stick to or is it better to close the gap. Mind you, mine as an 820.
Click to expand...
I would check the manual. 0.7mm is normal on a motorbike with electronic coil ignition.
I doubt Moto Guzzi has managed to change the laws of physics for the III ;)
The limiting factor is getting the coil back up to 12V before the next spark. We can juggle volts, charge (Coulomb), and amps but to get a healthy spark we need the coil at the full 12V, and which means no more than 0.7mm spark gap. A "firing pack" might use a larger gap, no coil as such. The coil windings ratio could be re-wound to give sufficient output volts to jump 0.9mm but then insufficient charge to ignite the fuel; the coil has to get back up to full charge in under 40 milli-seconds at idle nevermind at full pelt.
 
Brilliant thread, who would have thought such a simple question could produce so much information, better than any manual I've have ever read, I'll be paying a lot more attention to my plugs from now on.
Thanks folks.
 
Vagrant said:
BUT,!!! He is asking about a III not a 1 or a 2. The heads are different. It is 9 or 36 thousands.
Click to expand...
Hi

I am doing my 50,000 km maintenance on my 2017 v7iii and just noticed i have been setting the plug gap wrong. My manual says 1.92" which is obviously wrong so I assumed they misplaced the decimal and have used .020" ( like my old brit bikes) all these years. I have never had any problems, the plug colour is good and the bike performs perfectly. I just realized the metric spec of .9 mm is .035" and will use this.
Since everyone else in this thread seems to recommend .7mm I just wondered if you have any issues (as noted in some other replies) with your bikes using the .9 mm gap?
 
jefrs said:
The V7ii manual gives the plugs as NGK CPR8EB-9. The "-9" means they come out of the box at 0.9mm gap. The manual says gap should be between 0.6mm and 0.7mm. Which means they need adjusting from new. Many garages will fit them out of the box without re-gapping, which is wrong - it needs more volts as stated above, and can result in missing sparks particularly as higher revs. I re-gap the plugs with metric spark plug gap wires to 0.7mm, by go/no-go, the 0.65 passes, the 0.70 sticks, with the electrode faces parallel (which cannot be done with flat feeler gauges). I have experimented - gap of 0.5mm misfires all over the place, bike is unridable - gap of 0.9mm misses sparks like the battery is dead. Metric gauges are available; the rest of the world is all-metric and are thoroughly pained by trying to use the inch. Italy has never used that inch, you will find conversion errors in their literature.
Click to expand...
I agree that this is what the manual says - my V9 is the same
But it makes no sense to me that MG would specify a plug with a 0.9 gap when they could have specified it with 0.7 for example if that's what the bike needs
 
I always gap plugs, NEVER believe they are correct out of box. That is only for single electrode you can get to, multi electrode I use a wire type gauge seen as they are curved on the edge.
Do as the book says or .035"
 
tris said:
I agree that this is what the manual says - my V9 is the same
But it makes no sense to me that MG would specify a plug with a 0.9 gap when they could have specified it with 0.7 for example if that's what the bike needs
Click to expand...
It does not just apply to Moto Guzzi but pretty much any vehicle (modern cars with "firing packs" can be a bit weird). There is some difference in time constant between points and electronic. Points, old school 0.025-inch "25-thou". With electronic 0.70mm, that final nought means +/-0.05mm. I actually experimented with a bike, a single with gaps of 0.5, 0.6, 0.7, 0.8, 0.9 mm. The 0.5mm produced random sparks all over the place, the bike would not run. The "out of the box" 0.9mm misses at high revs, there's not enough time for the charge to build up enough to jump 0.9mm at high revs.
 
I thought that iridium plugs as fitted to most modern bikes are non-adjustable because of the risk of damaging the central electrode?
 
I thought that iridium plugs as fitted to most modern bikes are non-adjustable because of the risk of damaging the central electrode.
 
Sorry. I withdraw these double posts. It is, of course, possible to adjust the gap on an iridium plug. Mea culpa - early senility……
 
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