Hitchcocks Forum

Hi all,

I wonder if anyone can shed some light on why my spark plug in my bullet efi 500 keeps fouling and getting covered in carbon?

I had a problem with bad idling but managed to rectify it after changing the bad plug but unfortunately 7 days later I had the same problem. I know that I'm using the correct plug for the bike but it's happening almost after every journey. Yesterday I managed to start the bike first time after a 2 week 'rest' but 30 minutes later when I came back out to start my journey it wouldn't start. I changed the plug for a new one and hey presto...

Now most of my journeys are slow commutes to work and I've read that a higher temp plug may be more suitable, could this be right?

Also, I can't guarantee it 100% but I'm pretty sure the I check that the 'choke' is fully off before I ride so unless it's faulty I don't think it's that...

Steve

I don't have an efi so might be corrected, but I seem to recall other efi riders having issues with the standard fitted plug. Is it not a chinese made bosch or something odd? Anyways, the usual answer, certainly on the usa enfield site, is to bin it and fit an ngk plug (whilst being aware of the huge number of snide ngk plugs on the market). Someone will be along soon no doubt with the correct grade or of course you can always phone Mr H for advice.

What sort of carbon sudburys, "dry" black soot or more "wet" shiny stuff.

Not wanting to be ‘funny’, but if the plug keeps failing then it isn’t the correct plug for the bike and the use being made of the engine. Especially in cold weather and given the fairly slow journey you take I’d suggest the problem may be an incorrect heat range – a common problem on Bullets. For this time of year and for most types of riding the recommended plug is, in my opinion, too hard. It never gets sufficiently hot to self-clean and the consequent carbon build-up initiates a vicious-circle of reduced heat and increased likelihood of failure. Try a grade or two softer (hotter) plug – with NGK, go from say a 7 or 8 to a 6 or 7 grade. Keep an eye on the plug after making the change, just to be sure it’s not too ‘soft’.

Perhaps your TPS unit is within factory spec, but running at the richer end of it.

NGK heat ranges go the opposite way to Champion et al. The recommended NGK (standard) plug is a BPR 6ES. Try a BPR8ES. If it's that bad I doubt that it is the plug anyway, if you've already changed it. When mine showed the symptoms you have it turned out to be the tps connector having become detached....I assume that the plug is sooty black (rich mixture) not oily black (oil burning). If the "choke" is stuck on it doesn't cause rich running; all it does is the equivalent of holding the throttle open a little as it isn't really a choke. If it has stuck on you'll just get higher than normal engine revs when the engine has warmed up. The fault finding logic for these EFI bikes differs in some respects from the more traditional Bullets.

Not having a good day today. Standard plug is as stated, but if it fouls you need one with a lower number eg 5ES. I was thinking the normal way of heat rating. Sorry.

Once the plug starts fouling it misses sparks which leaves unburnt fuel in the cylinder, that makes it run rich and creates soft fluffy carbon, which makes the plug foul, which...

I've just had this happen with the NGK iridium plug. That has a very small electrode so once that gets fouled it can't find another spot to spark properly from.

I'm using Redex in the tank and italian tune-up to try and burn it out. The engine has to be got hot to burn out carbon like this. I may have let the motor idle too long but I don't ride all that slowly so I'm not too sure of the cause, I'm leaning towards 'wrong plug'.

The motor is air cooled so much depends on how hard you make the engine work esp in cold weather.

The Bosch-India plug I had from new was badly corroded, if you're still using one then bin it, netter still drop it in a neighbours bin up the street, you want it as far away from your bike as possible.. NGK BPR6ES or Bosch WD7DDC4 which has two electrodes (which may be better, and is the stock plug type). Do note that double-D which means twin electrode, C is for copper, almost rocking horse poo and Bosch.de don't list them but H have them.



A plug with more ceramic cools the electrode more than one with a thinner ceramic electrode insulator (that's inside the plug, the 'nose'). The thinner insulator gets the electrode hotter and so burns carbon off of it better but it won't make the engine run hotter or colder; it has to be matched to the engine's combustion chamber temperature. With the EFi the plug colour is meaningless. Examining the plug works with a carb but this motor is 'lean burn'. I can never remember which way is hot and cold or hard and soft for plugs nevermind the plug numbering systems. Apparently Bosch '8' is hotter than a Bosch '7'.

tpyo - "better" not "netter". There is a Bosch WR7DC which is the wrong plug and not to be confused with Bosch WR7DDC

Hmm, I find this forum/message board extremely frustrating to use. Though by no means a touch typist, I'm reasonably proficient and I believe what happens is that I type too quickly for the web-based board to keep up, so it seems to lag with strange results. It's even worse on my iphone with predictive text and the frustration is compounded by the feeling that I've got to get a move on with a lengthy post or I'll lose the lot when I getted logged out. Not having the facility to edit within the message board only adds to the trouble I have. (Yes, I know I can copy and paste, but it's all a bit tedious really). Also, having no access to emojis (as far as I know) means one can't easily express tongue-in-cheek comments etc. I'm afraid life is too short (at least life pre-arthritis is) to spend time trying to fathom how to post a picture. I'll leave that to those who can and want to do so. I've only recently managed to install Windows 10 on my dual boot laptop that had Linux and Windows 7 on it; I learned a lot about boot loaders and cracked it in the end, so I'm not exactly computer illiterate, but on balance I'd rather be riding or tinkering with my bikes than annoying people on here too often.