oldgrumps Posted November 3, 2015 Report Share Posted November 3, 2015 My evo came with a ngk bpr 7es plug. I swear I read in the manual the plug was the bpr. Was going to pick up a few extra plugs so to double check I opened the manual online which says ngk br7es. Which one is it? Old Quote Link to comment Share on other sites More sharing options...
heffergm Posted November 3, 2015 Report Share Posted November 3, 2015 They're the same heat range, the P is just the protruding electrode version. My 2013 used a br7es fwiw. I wouldn't expect the 2015 is any different, but I don't know for sure. Quote Link to comment Share on other sites More sharing options...
oldgrumps Posted November 3, 2015 Author Report Share Posted November 3, 2015 Thanks, I guess you could just run either. Quote Link to comment Share on other sites More sharing options...
billyt Posted November 4, 2015 Report Share Posted November 4, 2015 (edited) The R stands for Resistor which is required when using a CDI as the Beta has. So there is a BP which is non resistor type and BR which has the resistor. Buy the BR7ES resistor type which is the correct plug. Edited November 4, 2015 by billyt Quote Link to comment Share on other sites More sharing options...
dadof2 Posted November 4, 2015 Report Share Posted November 4, 2015 Do a search on NGK resistor spark plug technical information. Many use non resistor plugs with no ill effects but why take the risk Quote Link to comment Share on other sites More sharing options...
heffergm Posted November 4, 2015 Report Share Posted November 4, 2015 (edited) This is what the 2014 owner's manual specs, and what came on my 2013 (i.e. as delivered from the factory, it had a br7es fitted, not a bpr7es): Spark plug ............................................................................ NGK BR7ES Edited November 4, 2015 by heffergm Quote Link to comment Share on other sites More sharing options...
steve_earle Posted November 4, 2015 Report Share Posted November 4, 2015 In the U.K and other cold climates alot of people use the BPR6ES, Runs cleaner if you use low revs alot of the time! 1 Quote Link to comment Share on other sites More sharing options...
tlrmark Posted November 4, 2015 Report Share Posted November 4, 2015 In the U.K and other cold climates alot of people use the BPR6ES, Runs cleaner if you use low revs alot of the time! Oldgrumps lives in the tropics. Hawaii Quote Link to comment Share on other sites More sharing options...
oldgrumps Posted November 4, 2015 Author Report Share Posted November 4, 2015 I'm 99.9 percent sure the BPR is resistor type plug. The difference between the BPR and the BR is the projected plug tip. Old 1 Quote Link to comment Share on other sites More sharing options...
thesolidman1 Posted November 5, 2015 Report Share Posted November 5, 2015 The owner manual (CD) for the '15 models states 125-200 cc use BR7ES, 250-300 cc use BPR7ES Quote Link to comment Share on other sites More sharing options...
dan williams Posted November 5, 2015 Report Share Posted November 5, 2015 As Billy observed you can't go wrong with the stock plug. The resistor plugs actually came about to suppress radio noise in autos. By reducing the edge rate of the spark the resistor plugs reduced the radio waves generated by the ignition firing. They also slightly increase the duration of the spark while dissipating a small part of the available energy. Performance wise there is virtually no difference. Cleaning your air filter will make a much larger difference. Can you blow up your CDI with a non-resistor plug? Very unlikely. Consider how the CDI works. A coil charges a capacitor up to around 300V. The charge in this capacitor is dumped through the primary of the ignition coil by triggering an SCR. The SCR is similar to a transistor that acts like a switch. A pulse of current from the trigger coil (yeah the bit that usually fails on a Beta stator) shorts the SCR. I admit that's a bit simplistic as the modern CDI has a microcontroller in it that senses the trigger pulse and adds a delay to the trigger based on engine speed (which is how you can have programmable ignition curves). So this large current of respectable voltage gets dumped into the ignition coil which is actually two coils with a common core A.K.A. a transformer. The primary winding which is thicker wire with less turns to build up a nice strong magnetic field, and a secondary winding with lots of turns of smaller wire to build up a nice high voltage in the tens of thousands of volts at a still respectable knock you on your ass current. The spark plug gap in the cylinder is what's called a negative resistance device like a flash bulb or a lightning bolt. With no voltage across it presents a resistance of many giga Ohms. As the current in the ignition coil secondary builds up it has nowhere to go causing a voltage to build across the plug gap. It's worth noting at this point that the 10kOhm resistance of the plug cap and/or resistor plug in series with the giga Ohm resistance of the gap is insignificant. As the voltage builds up the air fuel mixture in the plug gap starts to ionize. Electrons are stripped away from the atoms in the gap and a path of ionized gas is created between the electrodes. Once this happens the resistance of the plug gap effectively goes to zero. When this happens the energy stored in the magnetic field of the coil is dumped across the gap. Since the resistance of the gap is now nominally zero the voltage out of the coil drops as the current is dumped across the gap creating the hot part of the spark. Now the plug/cap resistance come into play limiting the peak current the secondary winding can dump across the gap and extending the duration of the spark. Current will continue to flow until the voltage of the secondary drops to the point where the mixture in the gap is no longer able to maintain an ionization path. The only possible mechanisms I can see for a non-resistor plug to damage a CDI is if a larger inductive kickback to the primary coil occurs. I think that's pretty unlikely though as the impedance looking back into the SCR is fairly low The projected tip plug is a similar story. In the early days the wide temperature swings of air cooled bikes running 32:1 mixtures had better plug longevity with projected tips because they are better at cleaning residue off the insulator. Modern water-cooled, electro-fusion cylinder bikes running at 80:1 - 100:1 oil ratios with higher compression ratios don't have the fouling problems so a projected tip plug isn't necessary. Will it hurt the engine? Not unless there is an interference with the piston. 2 Quote Link to comment Share on other sites More sharing options...
thesolidman1 Posted November 5, 2015 Report Share Posted November 5, 2015 . Will it hurt the engine? Not unless there is an interference with the piston. It's the OEM specified plug. Also for some reason, Beta has changed the spec for the plug to the projected tip version. Must be a reason for it. That said, I just checked my '15 and it has the regular BR7ES version in it. I'll give the project tip one a try. Here's what NGK says about it: A projected spark plug protrudes into the combustion chamber further and provides higher ignitability and improved performance. Simply this can be understood by representing the combustion chamber as a circle. A projected spark plug in effect produces a spark in the middle of the circle (or combustion chamber) allowing for an even flame spread. Conversely, a non-projected spark plug means the flame spread is not even. Quote Link to comment Share on other sites More sharing options...
oldgrumps Posted November 5, 2015 Author Report Share Posted November 5, 2015 (edited) Ok thats where I saw the bpr plug spec; on the cd that came with the bike. I'm sticking with the bpr plug since that is what my owners manual calls for. Thanks Old Edited November 5, 2015 by oldgrumps Quote Link to comment Share on other sites More sharing options...
dan williams Posted November 6, 2015 Report Share Posted November 6, 2015 I just meant in general the projected tip shouldn't be a problem. You never really know why some things get incrementally changed Maybe Beta got a deal on a big box of one type of plug or the other. Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.