Forum

[david bailey]

I have already noted that the factory fit Bosch spark plugs are inferior to the likes of NGK but cannot find a reliable source to tell me exactly which one? Lots of people make different recommendations some of which are clearly stated by the manufacturers as only being suitable for bikes up to 2017. Others seem to say that the plug cap also requires changing for a resistor or non resistor type so it all gets very confusing.

So which (not Bosch) spark plug for a 2020 Royal Enfield bullet 500 Trials and does the plug cap require renewal for a resistor/non resistor type with this new spark plug?

Thanks
David

[trophyvase]

I think you'll find that an NGK BPR6EIX iridium plug will do the job.
I'd fit an NGK plug cap too - with a resistor. NGK recommend that both plug and plug cap should feature resistors.

Hope that helps.

[david bailey]

Thanks for that I'll get one - is it easy to change the cap as there seems to be very little slack on my plug lead.
David

[several]

I also have a 2020 Bullet Trials that I bought new recently. In answer to your original query, an iridium plug is unnecessary in these crude low power engines and costs much more. Contrary to some comments, there is no power or reliability gain from iridium An ordinary suppressor plug NGK BPR6ES or the hotter BPR5ES will do just fine which are the equivalents of the original Bosch plug. Iridium lasts much longer which may be worthwhile in modern car engines where just accessing the plug requires a major dismantling, but in the Enfield the plug is easily accessible so no need for it. Ordinary plugs last well long enough anyway and because they are quite cheap, I'd rather replace them every few thousand miles than be stuck with a pricey iridium.

I fitted an NGK waterproof suppressor cap. Got a red one as I have the red bike. The old cap screws out of the HT lead and the new one pushes on. As you say it's a bit fiddly due to the lack of slack but it does go on. There is an existing rubber type sleeve on the HT lead you'll see when you remove the old cap. When you fit the new one, if you get the same type as mine, ensure the sleeve goes over the cap fitting, thus greatly reducing the changes of water or contaminants getting in to the cap.

The reason to have a suppressor cap and plug, as originally fitted on these bikes, is to prevent possible electomagnetic interference with the ECU. Very unlikely but there is no practical downside for not using suppressors so best to stick to these.

In due course I intend to replace the HT lead as the original may not be the best quality but that involves removing the tank to access the coil so haven't got round to it yet. Bought a length of it, also in red, to match.

Here are the Amazon links for these items:

NGK plug BPR6ES
https://www.amazon.co.uk/Genuine-NGK-BP ... 20&sr=8-14

BPR5ES
https://www.amazon.co.uk/NGK-Genuine-BP ... 20&sr=8-14

NGK suppressor waterproof cap
https://www.amazon.co.uk/NGK-LB05EMHRed ... 142&sr=8-5

[Haggis]

Change the HT lead as well.
The original one is rubbish and the plastic goes hard and perishes in no time.
A nice bit of copper core silicone lead will last a life time.
It screws into the coil the same way as the plug cap screws on to the lead.
I use ngk BPR5ES and cap YB05F-R.

[david bailey]

Thanks for that very detailed response - you have told me everything I need to know on the subject. I also have a red bike as I didn't fancy all the chrome on the green one. Now all I need to do is lower the seat a bit somehow and get the bike run in as I get in the way of all the 4x4's round here while I'm plodding round the back lanes trying not to do more than 40 mph! The bad news for them is that I won't be doing much more than 40 on most of the back lanes round here even when the bike is run in.
Thanks once again.

David

[Wheaters]

Conversely, the HT lead and cap on my 350 Electra are the 16 year old originals and work perfectly.

I fitted one of those “far more expensive and unnecessary” NGK Iridium plugs ( actually only cost me £9) and I’m very happy with it. Obviously, I could have fitted a copper cored one for a whole £4 less and changed it twice as often. Hang the extravagance, I say.

[Breezin]

I've seen it said many times that the Bosch plugs are inferior, but I haven't seen any reason stated as to why. Can I ask how this is experienced?

A sparkplug seems a rather basic standard piece of tech at this stage.

[Haggis]

David, you dont need to stick to 40mph, infact you'll be doing more harm than good if your in top gear at that speed.
Just gentle acceleration with a light throttle, 50 mph is more suitable speed for engine revs in top gear.

[several]

I've seen it said many times that the Bosch plugs are inferior, but I haven't seen any reason stated as to why. Can I ask how this is experienced?

A sparkplug seems a rather basic standard piece of tech at this stage.

I haven't personally experienced any probs with the original plug, which incidentally is their WQR8DC by Bosch India, fitted to the bike from new but was swayed by a number of reports from other owners as to its unreliability evidenced by misfiring and poor starting etc. Same with plug cap and HT lead.

I ran the bike stock with the original Bosch plug and whatever the cap was, to the first service which I did myself at about 300 miles and nothing went wrong with the HT circuit at all. It started and ran fine, no misfires etc. reported by some owners. Maybe I was just lucky or maybe it would have gone wrong with greater mileages but because a new NGK plug and cap is very cheap, I thought I'd install them. Nothing to lose and everything potentially to gain from using NGK.

I'd add that the latest UCE engines, the last of the production, appear to have been improved in this respect. On older UCE models the plug cap was a poor quality metallic looking thing and it is those which seem to have caused problems. But on my Trials it had a black rubberised cap, similar to an NGK. So it may well never have caused any problems but as I say, nothing to lose by going with the leading brand NGK.