• Welcome to the forum website of the Vincent H.R.D. Owners Club.

    Should you have any questions relating to the Vincent H.R.D. Owners Club, or Vincent H.R.D. motorcycles in general, please contact Graham Smith, Online Forum Webmaster by calling 07977 001 025 or please CLICK HERE.

    You are unrecognised, and therefore, only have VERY restricted access to the many features of this forum website.

    If you have previously registered to use this forum website, you should log in now. CLICK HERE.

    If you have never registered to use this forum website before, please CLICK HERE.

Use of Iridium Spark Plugs

AngloArm

Forum Website User
VOC Member
Greetings. Can anyone advise if I would improve starting on my '50 Comet C (standard 6 volt magneto) by using an Iridium spark plug? When I bought the machine it was fitted with an NGK B7ES for which the equivalent NGK Iridium plug is a BR7 EIX. I read that these plugs need 5000 volts less to spark. If not recommended what plug would you suggest.

Thanks

Richard
 

greg burt

Well Known and Active Forum Website User
Non-VOC Member
I used protruded Iridium plugs for years No Problems
Yes, they are a resisted plug , Resistors have been used for years , Page 113 Richardsons Book
I now use platinum Protruded Plugs , Bosch in 1 and NGK in another ,it's all about ignitability
NGK have a (DFE) Double fine Electrode) Ultra high Ignitability Spark Plugs
Bottom line is - Have a Healthy Mag , have it serviced so it will perform at its Best
 

BigEd

Well Known and Active Forum Website User
VOC Member
VOC Forum Website Moderator
If your bike is difficult to start due to ignition problems then an Iridium spark plug might help. They have an electrode made from an extremely corrosion resistant metal (Iridium) so the electrode can be made thinner but still have a long life.
The thinner the electrode the less voltage needed for a spark to jump a gap. You can achieve the same result by filing a standard plug to a finer point but it would need adjusting more often.
You can also close up the gap on your plug to 0.010" to give the magneto an easier time but you may then have fouling problems if your engine is oily. Also non-resistor plug caps and leads ensures any available voltage get to the plug gap.

I use B7ES in my Rapide. The ideal grade of plug depends on several factors such as state of tune, operating conditions and how oily your engine is. A smaller NGK number helps combat plug fouling if your engine is oily. A higher number is better for highly tuned engines that may be run hard for longer periods. NGK plugs seem to have a have a fairly wide heat range so within reason the grade is not too critical.

You say that you have a "standard 6 volt magneto". Magnetos do not use the battery or charging circuit of a bike but generate their own electricity so they are not 6 or 12 volt. If your ignition is 6 volt then perhaps you have a magneto body that has been adapted to take an electronic conversion in which case you need a good battery or charging circuit to run.

If the engine is in good tune and the carb is in good condition with fresh fuel then difficult starting is often an indication that the magneto needs attention. A new or different plug may help starting but it will not cure a failing ignition system.

Greetings. Can anyone advise if I would improve starting on my '50 Comet C (standard 6 volt magneto) by using an Iridium spark plug? When I bought the machine it was fitted with an NGK B7ES for which the equivalent NGK Iridium plug is a BR7 EIX. I read that these plugs need 5000 volts less to spark. If not recommended what plug would you suggest.

Thanks

Richard
 

Bill Thomas

Well Known and Active Forum Website User
VOC Member
Hello Richard, I tried these plugs, A lad from AUS told us to use a hard type. They cost the earth and my bike which had always been good became a pain!! And I am on D type dist'. Make sure the plug lead is a wire type, Not like they use on cars, And the plug cap is not a resistor type Cheers Bill.
 

Tom Gaynor

Well Known and Active Forum Website User
VOC Member
The (NGK) recommended plug for a standard Vin (Rapide, Shadow, Comet, Meteor) is an NGK BP6E, although if plug fouling is a problem, a 5 will be even better. I've run both. IMHO 7 is far too hard. (The plug for a Manx Norton is an 8.) The plugs with small centre electrodes carry the suffix "V". A plug takes less voltage to spark if the centre electrode and side electrodes are filed square with sharp edges. I suggest trying an NGK 5E before experimenting with something more expensive.
I've used NGK BP6ES without problems, in a variety of motors, for years, but stopped because I found new NGK plugs failing after a few hundred miles. This has been happening to me, and to others, for several years. There's been some discussion of it in the forum. I now use NoS Champion N9YCC (copper core), the exact equivalent of BP 6 ES.
There is no reason to use resistor plugs with a magneto (NGK resistor plugs have an R in the prefix) and good reasons for not using them: it may be true that they work if the mag is in perfect condition, but that's because if the mag is NOT in perfect condition, they will accelerate its demise. My twin wasn't an easy starter with NGK BPR plugs (they weren't labelled as resistor) until I added caps that weren't labelled "resistor" either. No more problems after that: there was no spark at all. I had to get the mag rebuilt.
My experience has been that starting problems are more often carburation... even if the mag is weak, it is at its strongest when cold, failing once it heats up.
 
Last edited by a moderator:
Warning! This thread is more than 12yrs ago old.
It's likely that no further discussion is required, in which case we recommend starting a new thread. If however you feel your response is required you can still do so.
Top