Autolite substitute for NGK BPR8ES

Anyone know the proper autolite plug? They didn't have the ngk's and gave me autolite 3923, and I don't think that's correct.

 

What bike is this for? The BPR8ES doesn't seem to be a match for the '85 XJ 700 N Maxim....

EDIT: I guess it does match according to Chacal. Every other website I found lists the BPR7ES


But you can check here:

http://www.sparkplug-crossreference.com ... _PN/BPR8ES

Looks like possible matches for the BPR8ES would be:

Autolite AR51
Autolite 4251
Autolite 4053
Autolite 51

 

I've been running BP8ES, but today looked in the XJ7600N owners manual and it lists BPR8ES (NGK) or W24EPR-U (Nippon Denso). Don't know why it would need resistor plugs, but that's what I am looking for.

 

So I have autolite 63's right now. I have a sooty plug and was wondering if 63's are resistance plugs. I can't find any info on the net and my multimeter sucks and is getting weird readings. I'm using resistance caps as well and hoping that's the reason for it being sooty.

 

I don't know if it works the same for bikes, or not........when I was growing up, our driver-ed teacher taught us that resistor plugs were used to cut down on the 'RF frequency' so that it didn't interfere with people listening to the radio or watching tv in houses or other automobiles that we drove past. How accurate that is, I have no clue. But that's the way I learned it.

 

And that's the way it is. The need for resistor plugs on motorcycles is to eliminate RF interference with the ignition system. Electronic ignitions don't like being interfered with.
If we had points ignition we'd be able to run without the resistor caps.

 

i've run mine without resistor anything without any problems. TV intrefearance went away with cable TV, radio went to FM, might still mess with the ball game on AM. ?

 

Might still mess up the unshielded transistors in the TCI. Note that I didn't say it definitely will, just that it can. Any unshielded electronic device is subject to "funky operation" when exposed to the sort of dirty RF that's generated by a spark ignition system.

 

Required to accept the interference by law, even!
Sorry, Im a ham. These things amuse me.

Anyhow, My bike came to me with NGK BPR7ES plugs in it. Im assuming this is a resistor type plug. Ive noticed someone in the thread say they have "resistor" caps and normal plugs. How does on tell the difference in the caps?

 

The R in BPR does designate that as a resistor plug. You can unscrew the plug caps from the wires and check them with an ohm meter to see if they are plain or resistor caps. My dad was a ham, so I am also easily amused by all things electrical.

 

So, then Im assuming that if one has resistor caps, they should avoid the use of resistor plugs then?

Im sure this has been covered before, but its the first time I have run across it.

 

So long as the total resistance is the same as what Yamaha specifies you can do whatever you like. I tend to stick with the stock arrangment to keep things easy for the next caretaker of my machines (resistor caps (the resistence varies depending on which XJ you have) w/ non-resistor plugs).

 

I fully intend to go out there with my multimeter and unscrew my caps today. Thanks for the heads up.

 

*ding*ding*ding* we have a winner! Bob, tell the man what he's won!

Resistance is the key. Some of our bikes came with resistor CAPS and specified non "R" plugs; those that didn't specify resistor plugs.

It's not just about radio interference. The total (recommended) resistance greatly affects spark duration and thus performance.

Yes, you can monkey around and play mixy-match. But I've also found the path of least resistance (sorry, couldn't resist, lololol) is to stick to the stock configuration.

Unless you have some RESISTANCE to the idea... (I just can't help it. It's irresistible...)

 

Ugh... the things that I forget to mention. Spark duration is a really, really big deal. Our engines were desighed to take advantage of a relatively long-duration spark (spark duration plays directly in to how combustion chamber design and valve timing are figured to give as near to an optimal burn as possible). Thanks for the reminder Fitz.

 

Interesting contradiction. My XJ700N owner's manual stipulates BPR8ES (NGR) plugs. My XJ700 Maxim Service Manual stipulates BP8ES (NGR) plugs. I decided to go with the BPR8ES plugs assuming the owner's manual is correct. My bike starts and runs great so I'm staying with the resistor plugs.

 

My 85 XJ700N had the 8's. My son in laws 86 XJ700N had 7's.
After my 2 carb conversion, I had 8's on the outside cylinders and 7's on the inside cylinders. I did this because the inside cylinders were a tad rich and I couldn't adjust it out with 1 carb for 2 cylinders. Worked out fine though.