Spark plugs

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tigman88

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Hi, I was wondering what you guys think are the best plugs to use on the commando
 
I have had the best luck with Champion N7YCs. NGKs seem to misfire.

Greg

'70 750 Commando
930 carbs
Boyer ignition
 
Well, opinions vary....

The BEST I've used are Denso Iridiums. A bit pricey but they're great plugs.

Failing that, I've no problems with NGKs.

Not really a fan of Champions, although my knowledge of/experience with them is quite dated, and they may be better these days.
 
Hi Tig,
Ive had nearly every NGK plug fail that ive put in my 750 commando. Ordinary NGK's & Iridium ones too.
I am now using Champions N7YC. The bike runs fine now & has done over 1000 miles on the current set of plugs. I did 300 miles the other weekend without any problems.
When I first rebuilt the commando it was running a bit rich on a single mikuni 36mm carb with boyer electronic, Boyer Power box, standard compression pistons & standard cam.
Now I have weakened the mixture & used champions the plug failure seems to have stopped.
The usual time for failure was when starting the bike after not using it for a couple of days & leaving it running on choke for too long. It may have been the choke making the mixture rich that caused the failures.
I run on super unleaded fuel as the octane is slightly higher than standard unleaded.
My commanmdo does smoke a bit if I leave it ticking over for a long time, so burning oil could be one of the reasons for plug failure.
I would try both NGK & Champion if I were you & discard any brand as soon as it gives you problems
Nowdays I always carry a couple of new spare plugs with me just in case.
Best of luck & enjoy riding your commando.
cheers Don
 
much like the oil debate..
but i like autolite AP63s - easily found and a platinum plug - very good plug and i do about 5-8k per season on 1 set with no problems.

I like champions, hate NGKs
 
I've used Champion N7s or N7YCs as they now are for more than 100,000 miles and never had a single one fail. A similar story with old Land Rovers. I just change them on the Commando when the outside starts to look corroded :)

When I trialled a Yamaha (OK it was a 2-stroke) then one or two from every box of NGKs was a duff one.
 
I've used NGKs since the 70s and always though they were "the best". I don't know what's changed but the last few years I've had various NGKs (including nearly new ones) fail in british bikes and not just Norton. I've gone back to RN7YC (with copper leads) and had no trouble since.
 
I ran thru every kind of plug imaginable until I finally got the ignition and carbs tuned in...Now I have the same BPR7ES plugs in there without trouble for over a thousand miles. Not saying they are the best, they just happened to be the ones I had on hand when I finally got everything else right. I am with Ludwig, if your plugs fail a lot, there is something else going on.

Russ
 
Most of the time I stick with NGK. I also use Champions from time to time. I have found them both to be good plugs. Years back I would not use a Champion in anything but they seem to have resolved their problems since. Of coarse the Champion company of years ago is not even the same company today. The one thing I have noticed is the NGK plugs tend to run a little cooler than the equivalent Champion. So if you have a bike that is a little on the rich side [most Nortons with Amal carbs] then you will likely find the Champions will stay running a little longer.
One thing I avoid is plugs with no plating on the threads. Of the heads I receive with siezed spark-plugs they are nearly always non-plated plugs. Jim
 
Sometime ago I read about autolite AP64 plugs running well in commando's that tended to run rich. I have a few in the garage that are marked norton, gap 35-40. I know the info came fromInoa list and I think this was a debate about 6-7 years ago on the same list. I generally use the NGK's though.
 
You can always make a bike that is a little rich run better with plugs that run a little hotter. But not nearly as well as it could run if the jetting were right. I have always found better performance going one step cooler than stock [NGK b8es] and then jetting leaner to keep the plug clean. Of course you need to have a working cold start enrichener or they will be hard to deal with cold.
Going hotter than stock on the plug is risking engine damage. If the bike gets leaner because the jetting has been corrected or a bit of dirt gets in the jet you can end up with a glowing electrode which will cause pre-ignition and damage the engine in a matter of seconds. Jim
 
I'd had more Champion dead right out a box than NGK. Best results in rich tuned slight valve guild oil leaking Combat was and is Bosch Platinum with 2 to 4 electrodes. I got great 6 months running hard and far on my 1st Combat-pre-Peel and not knowing even where points were located green novice by using these Bosch wonders. Other brand plugs tended to foul in a few miles, cleaned to only get a few more miles before misfiring stumbles. Its actually easiest to sit in saddle to change-clean plugs away from home. My buddy Wes before he re-did engine last year carried plug tools in his jacket and every stop or when missfiring caused a stop he wipe out tool suck out hot plugs and have em back in a few minutes. On our 04' Ohio trip I had to give him Peels Bosch Plat's and use his to get on down the road to rally. YMMV of course.
 
Hi all,
Ludwig is probably right about somthing causing the burning out of plugs but our Nortons are all getting old & lots of them are far from perfect. The fault on mine is probaly a rich mixture caused by the wrong jetting or burning too much oil & makeing it run hot, but if the champions run under these conditions then they are the plugs to use.
Its cheaper to buy different plugs that to have a rebore, buy new pistons, change valves & guides & replace all other worn parts.
I will look into buying a plug that is designed to run at a higher temperature & see what they run like.
Cheers Don
 
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