Replacing spark plug wires/boots/coils for 750?

TeddyG

TeddyG

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Location
Portland Oregon
To eliminate a possible cause for continual spark plug fouling (NGK B 7 and 8s) from my 750SF, I'm considering replacing the spark plug wires and boots, and possibly the coils. The battery cables were corroded, so I'm assuming the same for the wires and caps. I've searched the Forum and see MSD 8mm silicone wires/boots mentioned, but only see them sold in multiple sets. Can I use an automotive equivalent, and what type of plug boot and does it need to be non-resistor for the spark plug? Or is there an NGK model available? I made the battery cables myself using 4 gauge wire w/ copper crimped connectors.

Ditto on the Dyna coils- just buy 2 -3 ohm, and is there a specific power rating, etc, I need to know for ordering?

Thanks guys!
 
I buy copper core plug wire by the meter in any number of auto electricity supply sites. I usually use Vehicle wiring products and Auto electric supplies or their French outlets.
I use NGK 5 Ohm resistor plug caps obtainable from motorcycle suppliers.
I have used new Bosch coils on one of my 750s.
Paul
 
5K Ohm ( 5000 Ohm ), spark plug covers, when you can find them, 7mm copper core HT lead from motor mower shops also. Not Bosch GT40 coils,only on points if you must. Any Japanese 3,3 Ohm primary winding ignition coil will be adequate HTH j
 
B7 plugs! You are very game ... never run anything hotter than 9s in my SF1. Later transformed into more an SFC, now more modded again - never fouled a plug, never. If you're fouling plugs in an SF something else is wrong, so going for new ignition parts is a very good idea.
 
I disagree.
My high comp 750s are plug killers, S and SFC. Plugs are very choke sensitive. Ive' gone down from NGK 9s to 8 on both the S and the C.
Paul
 
Thanks guys,

The bike came to me w/ the B7 plugs (which the seller probably installed to rectify the fouling) and I bought new B8 and will also try Champion NC2. Based on the corroded battery cables it came with, I'm hoping new wires and caps will stop the fouling and then look into new coils if needed.
 
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Never had plug fouling issues on any of my previously own 750s and currently owned SFC running B9s.
Same as the 1200, I usually change the plugs because they're rusty. I fitted new plugs to the Motodd for my recent trackday, the ones replaced were the original ones I fitted when the motor was rebuilt in 2013.
 
Paul Marx said:
I disagree.
My high comp 750s are plug killers, S and SFC. Plugs are very choke sensitive. Ive' gone down from NGK 9s to 8 on both the S and the C.
Paul
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Very odd. Perhaps Euro fuel is causing probs, Paul? Of all the SFs I've worked on (years in a Laverda dealership included) or owned over the last 45 years I've never seen one foul a plug - and they all used B9s. Choke use had no bearing on it. My SF motor ran 10.25:1 for decades on B9s.
 
piranha-bro2 said:
Very odd. Perhaps Euro fuel is causing probs, Paul? Of all the SFs I've worked on (years in a Laverda dealership included) or owned over the last 45 years I've never seen one foul a plug - and they all used B9s. Choke use had no bearing on it. My SF motor ran 10.25:1 for decades on B9s.
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It's only been happening the last few years.
They all appear to be running rich. I've gone down 10 points on the S pilots, 5 on the SF2 and the 500.
There's no such thing as euro fuel by the way.
Paul
 
Paul Marx said:
It's only been happening the last few years.
They all appear to be running rich. I've gone down 10 points on the S pilots, 5 on the SF2 and the 500.
There's no such thing as euro fuel by the way.
Paul
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Fuel for Australia will be different to fuel for Europe- they change the formula to suit the seasons, more volatile in the winter for ease of starting. I doubt Australia would need a volatile mix for cold starts. Saudi petrol is almost pure, no additives and caused Jaguar fuel pumps to wear out! Reason your idle circuit is running richer is indeed modern fuel vaporising more easily, running rich at idle seems common , worse in hot traffic .
Your plugs are fouling because your still using points- electronic ignition would completely eliminate this!😂
 
Exmoor beast said:
Fuel for Australia will be different to fuel for Europe- they change the formula to suit the seasons, more volatile in the winter for ease of starting. I doubt Australia would need a volatile mix for cold starts. Saudi petrol is almost pure, no additives and caused Jaguar fuel pumps to wear out! Reason your idle circuit is running richer is indeed modern fuel vaporising more easily, running rich at idle seems common , worse in hot traffic .
Your plugs are fouling because your still using points- electronic ignition would completely eliminate this!😂
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Even on my Electronica?

As I said, there's no such thing as Euro fuel. The climate in Finland is very different to that of Grece. Not to mention legislation and taxes.
Paul
 
I should clarify by saying the bike is stationary and still being sorted out, so perhaps thats causing the plug fouling. I pulled the spark plug wires and see there's not much of a connection to the coil, and I'll be replacing the wires w/ 7mm copper, a better connection to the coil, and new plug caps. I tested the coils and seeing 3-4 OHMS primary and 10 for the secondary.

Most fuel here has ethanol but I'm using only ethanol free premium on this bike
 

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As notables here proffer, fouled plug will not be attributable to faulty ignition, apart from wet fouled from unburnt fuel. If sooty then that is confirmation that the ignition HT is working, burning an over rich mixture, or excess oil in the combustion chamber. HTH j
 
Thanks- I'm trying to rectify the plug fouling by checking any possible causes. It's possible the bike needs to be ridden under load to prevent the fouling. I recently bought it and it required extensive servicing including new carb O rings, gaskets, and new slides will be installed next. I've checked the valve clearances, points gap, and ignition timing is spot on one cylinder and slightly advanced on the other. It fires right up, but won't give even carb synch readings possibly due to the scored slides. I've tried both lean and rich settings on the mixture screws with not much change to fouling. A leak down test showed no audible hissing and compression test 130 lbs both cylinders. The plug fouling immediately made me think too rich a mixture but it idles better at start up w/ less enricher needed when mixture screw is turned out more from the default 1.5 turns out, and turning screw in results in more enricher needed. B7 or B8 plugs both foul the same and next I'll try Champion NC2s. Next time I get it running I'll take it around the block and look at the plugs.
 
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TeddyG said:
Thanks- I'm trying to rectify the plug fouling by checking any possible causes. It's possible the bike needs to be ridden under load to prevent the fouling. I recently bought it and it required extensive servicing including new carb O rings, gaskets, and new slides will be installed next. I've checked the valve clearances, points gap, and ignition timing is spot on one cylinder and slightly advanced on the other. It fires right up, but won't give even carb synch readings possibly due to the scored slides. I've tried both lean and rich settings on the mixture screws with not much change to fouling. A leak down test showed no audible hissing and compression test 130 lbs both cylinders. The plug fouling immediately made me think too rich a mixture but it idles better at start up w/ less enricher needed when mixture screw is turned out more from the default 1.5 turns out, and turning screw in results in more enricher needed. B7 or B8 plugs both foul the same and next I'll try Champion NC2s. Next time I get it running I'll take it around the block and look at the plugs.
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It's good that you're going through the list Teddy. You can eliminate scored slides as a cause of fouling - from memory, your slides actually looked in good nick, but even when badly worn (like right through in heavy 'chafing' areas) it won't cause plug fouling.
Not sure why you can't get ignition timing spot on for both cylinders? You can make a very slight increase or decrease in points gap to allow the timing to be set within the available slots.
From what you're saying, you are getting uneven readings using a vacuum gauge to set the carb sync?? It really isn't necessary to use vac gauges on twins if you're just getting the thing running (and TBH I've never used vac gauges on my or anyone else's twins) - for initial startup just wind the throttle stop screws right out until the slides seat in the bottom of the carbs and adjust the cables so the slides both lift at the same time. Again, slide wear won't make any diff unless severe.
Really sounds to me like an ignition system cleanup will do the trick - all contacts (including if you're running everything through the main key switch ie no relay), contacts through switch blocks and onto coils etc. A weak spark would likely cause plug fouling.
 
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