Spark plug colour

Previously nick_ohare wrote:

Hi advice welcomed Here is the situation. 72 750 fettling to get back on the road.

1) Carbs replaced with new Amal 932s. Plrobem of intermittent misfire when cold and occasionally when accelerating from 2000 to 4000 rpm (seems ok over that but I dont ussually hold it at that for long)

2) Repalced the Champion N7YC with N6YC. Took four kicks not the usual one t or two to start. Same misfire symptoms as above. No difference really.

Checked plugs after a 20 minute run up and down the rev range. New plug's N6YC electrodes are now white Pic1. N7YC that were in the bike when bought a month ago Pic2

It seems that I am now running a weak mixture even though no changes have been made to the carbs. Any thoughts? Thanks Nick

Previously nick_ohare wrote:

Hi advice welcomed Here is the situation. 72 750 fettling to get back on the road.

1) Carbs replaced with new Amal 932s. Plrobem of intermittent misfire when cold and occasionally when accelerating from 2000 to 4000 rpm (seems ok over that but I dont ussually hold it at that for long)

2) Repalced the Champion N7YC with N6YC. Took four kicks not the usual one t or two to start. Same misfire symptoms as above. No difference really.

Checked plugs after a 20 minute run up and down the rev range. New plug's N6YC electrodes are now white Pic1. N7YC that were in the bike when bought a month ago Pic2

It seems that I am now running a weak mixture even though no changes have been made to the carbs. Any thoughts? Thanks Nick

Hello well hear some Spark plugs that self clean NGK BR7ET or Bosch W7LTCR these are both mid range heat, suits your Commando Engine But Check them out first,, yours Anna J

Hi Tony and Anna,

Thanks both for your info. I tracked down a pair of NGK BP7ES plugets and got NGK equivalents in the palladium version. Havent had a chance to try them yet Friday is the next chance. I will track down the Bosch plugs too. I think it is worth trying to find the best to suit the bike and the nasty fuel we use. Nick

Hello the NGK BR7ET are Three point spark plugs like Bosch ones , there Self Cleaning for this nasty fuel we now have to use , Happy riding in the sun , yours anna J

The advance and retard on the Boyer can be suspect it tends to be unstable at low revs. I'm not sure how you would test it, other than with a timing light and posibly the primary cover removed to see more of the degree guage.

Regards Alan

Previously nick_ohare wrote:

Hi all, Chabged the plugs for NGK Palladium versions of the BPR7ES. Miraculously, NO Misfire! Great news. However:

1) Right hand plug white (ish) but definetly lean.

2) Left hand plug more of a tan colour so OK but still the lean side of ideal?

3) Had the tank on and off multiple times as I have been struggling with wiring and the carb control cables (revs up with bars to the right, cuts out bars to the left). Finally got it running right an ticking over at just shy of 1000 rpm. The problem is that stud that scews into the tank is unscrewing with the nut at the bottom. Tried thredlock but need something more tenacious. Any suggestions?

Cheers Nick

Not too sure of the set up on early tanks, but if the 'stud' is reversible, i.e: same thread both ends, would it be possible to do just that? Then the more tenacious thread goes in the tank, and the 'not so' end gets the nut, which can be helped by an appropriate washer, maybe...?

Previously robert_tuck wrote:

Just to make it clear,It was running reasonably but with a bit of missfire and the plugs looked a fair colour. A change of plugs (and nothing else) and we have some very omminous looking plugs.

I tried some lodge 2HLN plugs and the colour of the insulator was pink no matter what the heat in the engine or mixture or anyrhing. !!

I didn't even have to take the plug out !!!!!! So maybe 'LODGE' brand is the answer

Cheers Colin

Hi. i haven't got a commando but just a thought if there are two separate coils one for each plug there could be an output difference between them with reference to plug colour. also if an oil cooled coil is mounted on its side it slowly leaks loosing its oil that cools it and the coil will just burn out in time. if there are any dents on any of the the coils around the bracket area i would replace them it would cause a shorting out inside on the caseing more so in damp conditions. just trying to help. Baz

Previously anna jeannette Dixon wrote:

Previously Phil Hannam wrote:

The proof is usually in the pudding..........or in my case road testing. I fitted a new single Amal Premier 32 Concentric to my 750 Commando in March of this year. I have now done over 1000 miles including the Irish International last week. I got it from Surrey M/Cs because Amal informed me they had a 6 week waiting list and also could not give me any info regarding a single carb set-up. The main jet was a 220. I was concerned that this was a bit low in view of running a Mercury with a 930 and 260 main. I was assured that this would be ok as the new carb was manufactured much better. However, an obvious alck of oomph and a plug check led to a 240 main jet plus K&N cone filter. This resulted in a light brown plug colour and 55 mpg at 70 mph.

I got a miss-fire while riding across Wales in the very heavy rain. Wet electrics being the cause. A clean up around all the major connections sorted this and I was able to paddle home.

I use either NGK BP7ES or Champion N7Y plugs with a Pazon. All ok. As the original posting mentioned a miss-fire in a specific rev range then I would recommend checking the parts of the carbs that cover that. I would also be checking the whole wiring loom for a wire shorting out on the frame.

Hello Your all using the wrong type of spark plugs for E5 fuels Bosch are better than Nkg or any other make they where the first too make spark plugs anyway , there Three point Plug give a direcet spark to the fuel and are And shelded type of spark plug this mean it shelded from Fouling and glasing in the procilin witch then make a earth so the half the spark runs to gound under perssure, relsuiling in a miss fire, you need something like FR7DTC Check out the Bosch range but the heat range is from 6 to 7 on the chart find out more at www.boschsparkplugs.com yours anna j

Nice but DimPSorry I know the current Plugs thread is pretty well played out but i"m still a bit confused .Like most of us,i"m a sucker for a bit of techno go faster kit,especialy if it"s only a few quid. Reading the thread, I thought Anna had reccommended Bosch fr7 dtc only for this to be gazumped by w7L tcr a few responses later . Mines an 850 by the way. Also on another tack, I can"t seem to get the damn end screw thingy off. If the plug already has an integral supressor , then like to use caps without an extra one built in! It seems welded on or something, or am I just being feeble Many thanks

Previously tony_clements wrote:

Previously nick_ohare wrote:

Hi advice welcomed Here is the situation. 72 750 fettling to get back on the road.

1) Carbs replaced with new Amal 932s. Plrobem of intermittent misfire when cold and occasionally when accelerating from 2000 to 4000 rpm (seems ok over that but I dont ussually hold it at that for long)

2) Repalced the Champion N7YC with N6YC. Took four kicks not the usual one t or two to start. Same misfire symptoms as above. No difference really.

Checked plugs after a 20 minute run up and down the rev range. New plug's N6YC electrodes are now white Pic1. N7YC that were in the bike when bought a month ago Pic2

It seems that I am now running a weak mixture even though no changes have been made to the carbs. Any thoughts? Thanks Nick

Hello well hear some Spark plugs that self clean NGK BR7ET or Bosch W7LTCR these are both mid range heat, suits your Commando Engine But Check them out first,, yours Anna J

Previously alec_stevens wrote:

Nice but DimPSorry I know the current Plugs thread is pretty well played out but i"m still a bit confused .Like most of us,i"m a sucker for a bit of techno go faster kit,especialy if it"s only a few quid. Reading the thread, I thought Anna had reccommended Bosch fr7 dtc only for this to be gazumped by w7L tcr a few responses later . Mines an 850 by the way. Also on another tack, I can"t seem to get the damn end screw thingy off. If the plug already has an integral supressor , then like to use caps without an extra one built in! It seems welded on or something, or am I just being feeble Many thanks reviously anna jeannette Dixon wrote:

Previously tony_clements wrote:

Previously nick_ohare wrote:

Hi advice welcomed Here is the situation. 72 750 fettling to get back on the road.

1) Carbs replaced with new Amal 932s. Plrobem of intermittent misfire when cold and occasionally when accelerating from 2000 to 4000 rpm (seems ok over that but I dont ussually hold it at that for long)

2) Repalced the Champion N7YC with N6YC. Took four kicks not the usual one t or two to start. Same misfire symptoms as above. No difference really.

Checked plugs after a 20 minute run up and down the rev range. New plug's N6YC electrodes are now white Pic1. N7YC that were in the bike when bought a month ago Pic2

It seems that I am now running a weak mixture even though no changes have been made to the carbs. Any thoughts? Thanks Nick

Hello well hear some Spark plugs that self clean NGK BR7ET or Bosch W7LTCR these are both mid range heat, suits your Commando Engine But Check them out first,, yours Anna J

the thing is the fuel type has changed from the fuel that was used when these Nortons where new , and compress may of changed has well so the spark plug the was recommed back in there day will have a job the fire this new type fuels has it has a single ground electroid with a smallish flame cornel , so if you then change and try out the 3 point ground electriods with a derect flame conel has a bigger fat spark to cope with modern fuel under higher pressures, The way My Great uncle Freddie tuned his engines with exhaust pipes off so he could see the colour of the fames coming out of the exhaust ports fun and games

yours anna j

Previously nick_ohare wrote:

Previously alec_stevens wrote:

Nice but DimPSorry I know the current Plugs thread is pretty well played out but i"m still a bit confused .Like most of us,i"m a sucker for a bit of techno go faster kit,especialy if it"s only a few quid. Reading the thread, I thought Anna had reccommended Bosch fr7 dtc only for this to be gazumped by w7L tcr a few responses later . Mines an 850 by the way. Also on another tack, I can"t seem to get the damn end screw thingy off. If the plug already has an integral supressor , then like to use caps without an extra one built in! It seems welded on or something, or am I just being feeble Many thanks

Hi Tony, as I havent got to the bottom of this I hope the wise heads still proffer their five bobs worth! I am on plug comparison mission, 2 types of Champion, 2 types of NGK. I reckon I have some more detective work to do. Trouble is that plug colour is our only window we have to see what combustion has been like.

The suppressor caps are always coming loose in my experience, try WD40 and a pair of grips?

I am beginning to suspect the advance / retard on the Boyer is an issue. Anyone with opinions on this problem with electronic ignition?

Cheers Nick

reviously anna jeannette Dixon wrote:

Previously tony_clements wrote:

Previously nick_ohare wrote:

Hi advice welcomed Here is the situation. 72 750 fettling to get back on the road.

1) Carbs replaced with new Amal 932s. Plrobem of intermittent misfire when cold and occasionally when accelerating from 2000 to 4000 rpm (seems ok over that but I dont ussually hold it at that for long)

2) Repalced the Champion N7YC with N6YC. Took four kicks not the usual one t or two to start. Same misfire symptoms as above. No difference really.

Checked plugs after a 20 minute run up and down the rev range. New plug's N6YC electrodes are now white Pic1. N7YC that were in the bike when bought a month ago Pic2

It seems that I am now running a weak mixture even though no changes have been made to the carbs. Any thoughts? Thanks Nick

Hello well hear some Spark plugs that self clean NGK BR7ET or Bosch W7LTCR these are both mid range heat, suits your Commando Engine But Check them out first,, yours Anna J

Well after the Lord Mayor"s Show I know, but I would be interested to know what octane fuel Anna uses with along her all singing all dancing Boshe plugs? Does that make any difference? Thanks,Alec.

Previously alan_sessions wrote:

I had a similar experience last year with a new pair of Amals 932 (not premiers) for my mk3 850 - set them up exactly as the old ones but the bike ran poorly - I checked all the jets and channels - eventually took them off and put the the new slides and float bowl assemblies back on the old carbs and put them back on - it ran as sweet as a nut (and still like that after 3K miles) - can only assume there was a bad batch of Amal castings.

Hi Alan,

I had a similar problem (850 mk2) with a weak mixture on one cylinder and stuttering, bad starting etc, after fitting new 932 carb bodies. I eventually gave up trying to fix the problemand refitted the old worn original carbs and theproblem was cured.

Later I read a post on access norton refering to poorly made amal carb bodies, the problem being that the small core plug which is pressed in from underneath the carb body (next to the main jet) was not sealed properlyand allowed additional air to be drawn into themixing chamber.

That explained the weak mixture, stuttering and poor starting. Also the faulty carb would not respond well to mixture screw adjustment.

Hope this helps Nick.

Thanks for this info Nick - I can see the plug which covers the pilot jet outlets so will give them some sort of leak test - Alan

Previously gordon_robertson wrote:

Previously alan_sessions wrote:

I had a similar experience last year with a new pair of Amals 932 (not premiers) for my mk3 850 - set them up exactly as the old ones but the bike ran poorly - I checked all the jets and channels - eventually took them off and put the the new slides and float bowl assemblies back on the old carbs and put them back on - it ran as sweet as a nut (and still like that after 3K miles) - can only assume there was a bad batch of Amal castings.

Hi Alan,

I had a similar problem (850 mk2) with a weak mixture on one cylinder and stuttering, bad starting etc, after fitting new 932 carb bodies. I eventually gave up trying to fix the problemand refitted the old worn original carbs and theproblem was cured.

Later I read a post on access norton refering to poorly made amal carb bodies, the problem being that the small core plug which is pressed in from underneath the carb body (next to the main jet) was not sealed properlyand allowed additional air to be drawn into themixing chamber.

That explained the weak mixture, stuttering and poor starting. Also the faulty carb would not respond well to mixture screw adjustment.

Hope this helps Nick.