Let's talk about spark plugs.

What spark plugs for the 32 year old beast?
I need to find out the spark plug number and gap so I know what to buy.
Do any of those fancy plugs increase/restore performance and or gas mileage?


what about brand?
I heard a little about ngk iridiums that they can increase torque a little.

I know nothing on this subject.

 

Forum search "spark plug(s)". It's been talked about. Hope this helps.

Gary H.

 

Thanks rocs,
Care to point me to a particular thread? I did search but had trouble finding the answer to my question - about plug brand and types pros and cons. That sort of thing.

My forum search turned up four pages of results. THIS thread was the only thread with any relevant info about what I am looking for. The rest of the results where trouble-shooting threads far as I can tell without opening every result.

 

32 year old bike designed to run with a 'vintage' (inexpensive) spark plug design - I would stick with the stock recommendation from the manual.
I believe it is NGK BP7ES for my 81 XJ650 Maxim.

Snake oil on all that other stuff - if 3 electrodes are better than 7 would be friggin' awesome!

 

Would if i could. I've read several threads talking about this on the old site when i was recommissioning my 650. I've decided to stay with the stock plugs + resistant caps set-up. Sorry bro.

Gary H.

 

so this would be fine then? http://www.ebay.com/itm/Yamaha-XJ75...-Plugs-BPR7ES-x-4-2023-set-of-4-/160870157565

I have the Haynes Yamaha XJ650&750 Owners Workshop Manual but cannot find the part where it tells me EXACTLY the plug number I need. I found the above using google.

 

Pg. 147 section 9. Standard is NGK BP7ES (which i use) or ND W22EP. And or research catalog (it'll tell you) or send Chacal a e-mail; he'll tell you. Make sure you get the correct ones for your model. I also have a owner's manual that says these are the correct plugs for my 650j. Hope this helps.

Gary H.

 

The BP7ES (non-resistive) plug is stock for the XJ650 (except Turbo) and the XJ750 air-cooled models; the BPR7ES is the same exact same plug but is 5K resistive. The ignition system is set up to run with a certain secondary (plug-wire side of the coils) circuit resistance; in the stock set-up, the plug wires and the spark plugs are non-resistive, and the resistance in the circuit is provided by the plug CAPS (the hard plastic spark plug "boots", which have an internal 5K ohm resistor embedded within them).

You can use the resistive BPR7ES plugs, but you really should then change the stock plug caps to non-resistive BOOTS....this mean you'll need to crimp terminals onto the end of the stock plug wires, and use a flexible rubber BOOT to replace the stock resistive CAPS. Otherwise, you'll be doubling the resistance in the secondary circuit (from 5K per plug to 10K per plug). Although doing so won't kill the ignition coils, it will upset the factory-engineered balance in the system (higher resistance results in a longer spark duration, but at the cost of reduced spark power per unit of time ----- same total voltage output, but just spread out over a longer period of time, thus lower voltage at any instant in time over the longer time frame).

 

Been a long time since I was in one, but can't the resistors be pulled out? Just make a dummy from an appropriate bolt.....

 

On some (but not all) oem and/or aftermarket caps, he resistors can be removed and re-freshed (we actually have replacement resistors available for those that can). On some, they can't. Don't have the slightest idea why.

 

these have about 5000 miles on them with green dyna coils

NGK BPR7EIX IRIDIUM

 

I'd rather pay $2 a pop for stock plugs and change them every 2500 miles or so.

But those sure are some nicely balanced carbs and absolutely spot-on mixture-wise. TEXTBOOK it don't get any better than that.

 

i changed the coil and plugs at the same time and if you could flip a switch and go back to regular plugs and oem coils i think you could tell a difference. but if you changed it back on Wednesday and rode it Saturday i don't think you could tell a bit.
any change probably comes from the coils, but since i paid so much for the plugs i'am going to have to tell you their the greatest thing there is you know how that goes

 

I put in a set of these last time: http://www.e3sparkplugs.com/. Wouldn't say that it changed the performance any, but it does fire up a little quicker on a cold start. I also have Dyna coils.