Hello, I'm looking for a new spark plug and the DT1C parts manual says the spark plug is NGK B7E, however I can't seem to locate any of these so I assume there would be a replacement available - can anyone advise on this, thanks 

I’ve been using Autolite spark plugs MarkT turned me on to them I think they are better. 4054 autolite = B8ES its a colder plug than the B7ES

I use a B8ES in my 69 250 . Although the book calls for a B7ES , the colder plug colours up nicely .
I'd be really reticent using a B7ES with todays fuel . The Autolite suggested would be a good alternative .
As a side note Syd . One of our mutual friends with a Suzuki TS 250 ,( who shall remain nameless , to
protect the guilty ) burned a hole in his piston , using a manual specified B7ES ,
against my recommendation to use a B8ES .
 

All of the NGK B8ES, B7ES spark plugs should be available on eBay for a slight premium. People have them even though they were discontinued.

AsHo

the Lucas oil I am using in my bikes' yamalube systems probably makes a 1/10th of the smoke as what I remember back as a kid working in a small engine shop and leaves virtually no oily deposits on electrode (yes, pump outputs to spec), so I use a colder "9" in all of my bikes to reduce the odds of burning a hole in my piston.

Only exception is my little LS2 which called for a "7" so I went up to an "8" for same reason

Thanks for the info gents. My owners manual says B7E not B7ES - what's the difference? You can't seem to get B7E plugs now in NZ but the B7ES, B8ES and Autolite 4054 plugs are available. Oh dear, I didn't know our ex fearless leader burnt a hole in his piston..

Typo? There are B7ES and B7HS etc, where H is short reach and S is longer reach, but I haven't come across B7E plugs.  Doesn't mean they don't exist, of course! 

NGK added the "S" in the early 1970's.  B7E was replaced by B7ES at that time.

The designation after the "E" (thread reach and seal identifier) is the center electrode type.  I'm not sure if it was a "marketing move" or if they actually made a change to the center electrode metallurgy when they added the "S"? 

Anyway, a B7E was the basic standard spark plug and it was replaced by the B7ES...  the "S" was said to stand for "super wide heat range electrode" (No joke!) but most people assumed or called it "standard".  Another common electrode type for these NGK plugs is the "V" (B7EV) which designates a "fine wire center electrode".  I think NGK used gold palladium for the "V" plug center electrode.

B7ES or B7EV is fine. 

BR7ES is a resistor plug and can be used if you swap the spark plug cap for a non-resistor type.

BP7ES or BPR7ES should not be used as the "P" stands for "projected tip" which could cause engine damage. 

If it were me, I'd use the "8" heat range as others have suggested.  Yamaha went to an B8ES in 1971 on the 250 if I remember correctly.

NGK has web pages on how to identify counterfeit plugs... Ebay and Amazon have had problems with NGK counterfeits being sold.  Lots of NGK counterfeits out there. 

Thanks Mark! 

Here’s the email that you can send pictures to at NGK to understand whether a plug is genuine or not.  I was contacted by a real person with contact info and all, who asked me for a pic of insulator printing and the hieroglyphics on the steel base.  

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