[adrian]

I change the spark plugs of my Royal Enfield Standard 350 UCE every 10000 Kms. So last year I approached the authorized spares dealer in Trivandrum and asked for the spark plug combo designated for UCE 350s. Instead I was given the spark plug combo for UCE 500s remarking it to be an upgrade as advised by Royal Enfield. I declined the offer and contacted Royal Enfield as follows :



I must say that Royal Enfield was prompt to respond to the mail



The person in charge of the spare for this region contacted me over phone and after hearing my side, he remarked that it is indeed an upgrade of spark plugs.

On my mentioning the chances of the engine over heating due to the different heat range of the spark plugs, he hung up after telling that he will get back to me after contacting the company.

After a short while he called back and remarked that the Engineer from the company had commented that "with the spark plug upgrade, the motorcycle may over heat at full throttle on highways and it is perfectly OK to use for city rides".

When I commented that I won't use the upgrade on my motorcycle, the spares person assured that the old spark plugs will be available at Royal Enfield dealerships and that I will have access to them along with the upgraded plugs.

So there ended a happy conversation.

Extract of parts manual prescribing the spark plugs







Original plugs specified for 350 UCES







Now after 10K on my odo meter, I approached the authorized spares dealer in Trivandrum for the original spark plugs of 350 and got the reply that only the upgraded spark plugs are available.

I tried the luck at the spares division of Marikkar Motors Trivandrum and got the same reply - "the old spec spark plugs are not coming; only the upgraded ones are in stock".

I tried every spare shop in Trivandrum for the Bosch W5DC & UR5DC spark plug, but in vain. As a matter of fact, they are not available online as well

So I went back and bought the upgraded ones for comparison.

The so called upgrade - WQR8DC & UR6DC in place of W5DC & UR5DC



SPARK PLUG (M14) COMPARISON- W5DC TO WQR8DC







SPARK PLUG (M10) COMPARISON - UR5DC TO UR6DC






While the spark plugs are physically identical, the are of different heat ranges.

The change of heat range in the M10 plugs (5 to 6) is negligible but that of M14 plug (5 to 8) packs a risk of pre ignition.

So I won't be installing the upgrades in my 2011 Standard UCE 350.
I never had problems with the W5DC / UR5DC combo in my motorcycle and is tested with my experience.

So that brings up a few questions

1. With Royal Enfield withdrawing the spark plugs for older models and the lack of availability of them in local as well as online markets - What next ?

2. How risky is this heat range upgrade from 5 to 8 ?

BHP-ian Dr.Deepudev also found it difficult to find a replacement plug for his Thunderbird 350 UCE. But for the time being he was lucky enough to find a last piece at a spare shop in his home town.

I plan to contact Royal Enfield on the matter. So technical advises on heat ranges and the like please.

Thanks for bearing with such a long post.
regard Adrian

[Aditya]

Thread moved from the Assembly Line to the Motorbikes Section. Thanks for sharing!

[VW2010]

1. With Royal Enfield withdrawing the spark plugs for older models and the lack of availability of them in local as well as online markets - What next ?

2. How risky is this heat range upgrade from 5 to 8 ?

Its a Bullet. I use a four point spark for last 8 years. Spark plug availability is the least worry i have with any motorcycle as there are so many after market products that do wonderful job.

I would not be worried about this development. RE withdrawing barrel piston will only be my concern. Everything else available outside and the bike is generally repairable by oneself if they can sit some time to apply their common sense skill.

I have a 500 CI and I always look out for barrel piston in OLX.

[adrian]

Originally Posted by VW2010

I would not be worried about this development.

Sir, I totally agree with you. If you have the technical know how, you can dig up compatible spark plugs from the market.

In this case, the emphasis was on the attitude of the company in withdrawing the spark plugs of 350 UCE motorcycles of the 2009-2013 batch without any notification of any kind. After all it is not fair to leave the hands of their guinea pigs that early.

The reason for the spark plug upgrade, as specified by the dealer was "for emission control purpose".
May be their later 350 UCE models were designed to use spark plugs with a heat range of 8. But what is the effect of such an upgrade on a motorcycle specified to use a spark plug with a heat range of 5.

We here in Team-BHP look for minute details concerning our automobiles. Please think of people who gets a spark plug upgrade from the service centers without knowing what it will do to their machines.

If Royal Enfield is following this : The spark plug upgrade for emission purpose is most welcome, as long as you convince us that it is perfectly safe for our 2009 -2013 batch 350 UCE motorcycles.

As in this case : Why such a discrete circular on the spark plug upgrade to the parts dealers alone ? Customers deserve a notification of the same on your Official website.

regards Arun

[ArizonaJim]

adrian

First, I'll point out that many dealers try to put technical things into common terms for the common man who knows little about mechanical things.
The comment that this change by RE was "for emission control purpose" may be an example of this. Then again, that may be what RE told him and he is just repeating what he was told.
In either case, changing the heat range of a spark plug probably has more to do with people complaining about their engines running poorly because their spark plug has fouled than it does with emission control.

Although you have not had a problem with it, looking at the photo of your spark plug tells me that it is a bit too cool for your style of riding.
That is causing the buildup of fouling that shows on the center insulator.
Although this fouling is not a black carbon buildup which could cause mis-firing, a lighter tan or "off white" color would be better.

I tend to agree with the RE engineer about your overheating concern.

The hotter heat range spark plug should be fine for city riding and could only cause a problem if the engine was ridden for long stretches at high speed with a lot of "almost wide open throttle", or used for racing.

I am sure you already know this but for those who don't, using a spark plug with too hot of a heat range really won't over heat the engine. It can overheat the center electrode of the spark plug and in this overheated condition the center electrode can become hot enough to ignite the air/fuel mixture prematurely. That can cause the dreaded "Ping" or "Pink" as some call it. (It sounds like someone is shaking a metal box with marbles inside of it.)

At the moment, I would suggest that you install the hotter spark plug with the "8" heat range and ride the motorcycle normally for at least 500 km.
Then, remove the spark plugs and inspect the condition of the center insulator next to the spark plug gap.

If it is "off white" or a very light tan color and it shows no signs of blistering it should be fine.

If the insulator is bright white and has areas that appear to have irregular
glassy looking blisters on it, it is too hot and should be replaced with a cooler heat range spark plug.

By the way, the old "Iron Barrel" engines ran considerably hotter and due to this, the cooler #5 heat range plugs were commonly used.
The greatly improved aluminum cylinder head and cylinder causes the spark plug to run much cooler on the UCE engines is the reason the hotter spark plugs are often a better choice for these newer engines.

[adrian]

Originally Posted by ArizonaJim

adrian

At the moment, I would suggest that you install the hotter spark plug with the "8" heat range and ride the motorcycle normally for at least 500 km.

Sir, Thank you very much for your time for the detailed explanation on the matter. Will do as per your advise.

regards adrian

[rahul4321]

That's worrying. I have a '11 Electra and I hardly use it for riding in the city. It does only highways and with the roads in Gujarat and it almost full throttle most of the times. I'd hate to be stranded somewhere with an overheating bike just because someone at RE decided that it's easier to just manufacture one heat brand of spark plugs.

Not fair RE!

[ArizonaJim]

For what it's worth, my 2011 Royal Enfield G5 Deluxe (comparable with a chrome 500cc Electra model) came with a # 7 heat range Bosch spark plug.

There is not a great deal of difference between the Bosch #7 and the #8 heat ranges.
For the last 6 years, I've been using a NGK BPR6ES plug which is the equivalant of the Bosch #7 heat range and many times, I have ridden my motorcycle at an average speed of 100 kmph for distances of over 120 km without stopping without any signs of the spark plug overheating.

Actually, I was rather surprised to see that Royal Enfield had been using a #5 heat range on their earlier 350cc UCE's. That is 2 steps colder than the #7 and quite frankly, there is not a great deal of difference between the 350cc and the 500cc engines when it comes to the amount of heat either one of them produces.

I understand your concern but if the only spark plug you can get for your motorcycle from Royal Enfield is a #8, I suggest that you try it.

Ride normally on your high speed ventures and after you get to your destination, pull the spark plug and examine it.
I really doubt that it will show any signs of overheating.

Not being in India, I'm not sure what brands of spark plugs are available but many of us in the United States have switched over to NGK plugs.
If these are available, here are some equivalent spark plugs:

BOSCH UR5DC = Champion RG6YC, DENSO IU2O, DENSO U20EPR9

BOSCH WR5DC = Champian RN6Y, DENSO IW22, NGK BPR7ES, Autolite 62 or 63

[pedrolourenco]

I really do not see any issue with this. Spark plugs are usually not manufactured by vehicle manufacturers. Most spark plugs are either Bosch, Champion or NGK. I'm sure you can find an equivalent one from one of these manufacturers.

[adrian]

Had sent an e-mail to Royal Enfield along with the link to this thread.



Immediately received an automated reply that their team will get back to me. 8 days have passed and no response from that end.

Being Royal Enfield, I have no high hopes of getting enlightened by their support team.

[roshanjathanna]

Is RE still selling BOSCH w145Z1 plugs for bullet 350 CI engine ? I used to keep stock of these plugs earlier for my own use, now exhausted, looking for another 10 plugs

I know I can use W175Z1 which is easily available,but both belongs to different heat range.

[adrian]

Originally Posted by ArizonaJim

adrian

At the moment, I would suggest that you install the hotter spark plug with the "8" heat range and ride the motorcycle normally for at least 500 km.
Then, remove the spark plugs and inspect the condition of the center insulator next to the spark plug gap.

If it is "off white" or a very light tan color and it shows no signs of blistering it should be fine.

If the insulator is bright white and has areas that appear to have irregular
glassy looking blisters on it, it is too hot and should be replaced with a cooler heat range spark plug.

.

Been running around with the new spark plugs for a while (city rides only). Pulled the plugs out and there isn't any problematic signs. The central insulator is clean compared to my older spark plugs.

So I guess the upgraded plugs are not problematic for older machines. Appreciate the time of ArizonaJim for the detailed advice

P.S : Yet to test the plugs on the high way going WOT.