Forum

[Graham43]

Nigel thank you for your kind offer. I didn't buy the Bosch plugs after looking on the site, I got the plugs B9ES. I now think that it was most likely the wet sumping that caused the plug failure, but it has been an interesting discussion as always on this forum. Thanks again everyone.

[bikerhifinut]

Read this with interest.
Ok my outfit is a 2011 500 EFI so its the bosch twinspark plug variety.
Heres my experiences.
I had no real issues starting and slow running as long as the battery was healthy, using the Bosch Plug.
I Only had the one plug and no spare so I sourced a pair of NGK BP6ES (I thinks its that type, may be BPR6ES) based on a phone call to our hosts. I admit I got No1 nephew to get em but as he's in the motor trade may i be forgiven?
Now at first I was impressed with the NGK plugs, the bike seems to go really well on it.
The trouble started over the winter and short runs etc.
What seems to happen is that the NGK fouls up and if you are warming the engine a bit before riding off it starts to run rough and slow due to what I think is a poor spark. Eventually the darn thing won't start properly at all and I just get the Bosch out of my jacket pocket and swap it in and Bingo the bike will start on the kick starter with a half flattened battery.
So in future I shall get myself a couple of the twinspark Bosch jobs and that's the end of it. I dont care how cheap the NGK's were, if they are only any good if they are either brand new or as I found out, freshly cleaned of all the oily gunk round the electrode tip then they arent suitable.
Now I did notice something else with the NGK, the elctrode tip seems to have a slightly longer reach and although its likely less than a couple of mm maybe thats enough to get the tip nicely fouled up when the motors a bit cold. Not knowing the physics or chemistry of the combustion process this can only be a conjecture on my part.
Andy.

[Frank]

The longer the tip the hotter the plug which would burn off the deposits more readily in a cold engine.

[Presto]

There has been lot of disappointing experiences with various spark plugs on the EFIs, and while in no way doubting what is reported on this site, the whole thing seems a bit of a mystery. NGK have a superb reputation and I’ve never known one to fail. But they seem not to perform well in a range of different applications.

I did notice that Andy made a point that he wasn’t sure if the plug fitted was a BPwhatever, or a BPRwhatever. But there is a difference, and a BPR (R=resistor) type plug should not be used with a cap that contains a resistor. The result if they are used together is a decrease in current reaching the electrodes and a weak spark. Just a thought. But it would be useful to get to the cause of these failures - whatever it may be.

[Presto]

The difference between a hotter and a cooler plug is not the length of the exposed electrode but the exposed length of the ceramic insulator. A HOT (or soft) plug has a longer, thinner ceramic tip insulator, with more of the ceramic tip exposed to heat and less of tip in contact with the plug body. This reduces heat dissipation, and the plug runs at higher temperatures. A COLD (or hard) plug has less of the ceramic tip exposed and more in contact with the plug body, heat being dissipated more efficiently, allowing the plug to run cooler.

[bikerhifinut]

The plug hasnt failed, it just seems to make starting and slow running tricky. It seems to foul up easier, thats all I can think.
I did 50 odd miles yesterday on the NGK, the bike was a pig to start and only went after I had given the plug a good clean, even then it wouldnt idle, just slowing down until it stalled. This never happens with the Bosch. Strangely enough, after a good old "thrapping" over the N Yorks Moors, the bike started and idled impeccably, but I didnt have to do much slow running. I am still going to stick with the Bosch factory fitment in future though. It aint broke and I dont think I need to fix it. Oh and the fuel was fresh, Shell Optimax.
These are my experiences, and I have to say once its running and up to temperature the bikes quite a pleasant thing to ride.

Andy

[bikerhifinut]

I think I may have got to the nub of it.
The 500 EFI is running fine now using the NGK BP6ES after a decent run out.
2 things spring to mind, firstly the battery got a good charge up after getting somewhat flattened in the starting attempt and secondly I'd only run the engine up in the garage over the winter until it was warmed up just to keep the oil circulated and stop fuel going off in the lines. I think after a couple of those, the plug has basically just got clogged with deposits from idling and slow running and a good hard run out may have cleaned the pipes so to speak.
I tried it today after a couple of days idle and it started on the button immediately. The battery was obviously well charged judging by the willingness of the starter to turn. I normally use the kick start from cold but I wanted to see how well it worked on electric foot.
So my problems were possibly self inflicted to an extent, but I never had any of these issues with the Bosch. So on balance I think the NGK is fine if you use the bike for decent runs out but if you do a lot of shorter journeys maybe the Bosch is better suited. I'll be getting a couple of bosch plugs to stick in the jacket pocket instead of the NGK's.

Incidentally, whats this "wet sumping" malarkey? The EFI engines are a wet sump design anyway.
Andy

[Presto]

Thanks Andy for that feed-back – it partly confirms my view: that NGK plugs are not ‘rubbish’ or what-have-you. They are as good any plugs and better than most – provided they are used as intended. You are fair enough Andy to recognize that the use you put those plugs to over winter wasn’t really giving them a fair chance. <
>

There is a little point worth making about the Bosch for the GT Continental – it has a ‘Q’ in its reference. This indicates ‘QUICK HEAT’ – that means the ceramic near the tip is thinner than normal – the idea is to reduce build-up of deposits on the plug tip when starting from cold. The thinner ceramic prevents rapid heat dissipation through the central ceramic body – this allows the plug tip to retain more heat – which in turn allows the plug more efficiently to ‘self-clean’.

[bikerhifinut]

Good info presto.
I agree about the quality of NGK in general. Since starting motorcycling in the 1970's I rapidly developed a respect and preference for NGK plugs in whatever flavour of bike I had, from mundane eastern european 2 strokes through to high performance oriental Sportsbikes and a few sorts in between. I wont say I never "Cooked" an NGK but those incidents were usually due to hammering a 2 stroke at full chat for longish periods QED.
Yeah Plugs aren't as simple as many of us think and its good to learn what the numbers mean.
Andy.