How to gap a BKR6EKU plug

[TownsendsFJR1300]

so the plug manufacturers gap trumps the engine makers gap?

IMO, no.... One plug will fit different machines AND slightly different gaps per the manufacturer.

And not ALL the same plug # WILL be the same gap. Handling shipping, etc, can throw off a gap(ie some one drops a box, etc).

I would gap per Yamaha spec's but its apparent there's a typo in your manual.

As noted above, you shouldn't change the gap of the new plug more than .008" . Thus, the new plug should be pretty close if not on, right out of the box.

You also want to gap on the tight side (if need be). As the plug wears, the gap gets wider.

IME, I've found a "wire" spark plug gauge is a bit safer checking gaps, especially Iridium (precious metals easily damaged) plugs..

To eliminate and clarify for yourself, call NGK tech directly and speak with the tech department (I have previously). They can answer any questions W/O simply reading what the "internet says"...

[rodbolt17]

why not simply look at the Yamaha Marine Technical guides?
they explain both methods with words and pictures.
you can use a .o24" pin vertically between the insulator and the ground electrode or a .062" pin horizontally between the center electrode and the ground electrode tips.

[428street]

I'll call NGK.

rodbolt17, I'm not a marine mechanic and am not aware of the Marine tech guide. I am mechanical and like to do my own stuff as much as I can not because I'm trying to save money but because I like to learn and I have some time. That being said, the first thing I did was directly consult the manual that came with my engine which I thought was the defacto correct place to go for settings and specfics...apparently that is wrong so I will have to start all over again and maybe even call Yamaha but my guess is they will direct me to a dealer and have to do that dance.

I did not expect this to be this much of a can of worms but it is...

[TownsendsFJR1300]

Your owners manual as a PDF:

http://www.yamaha-motor.com/assets/s...07-03_1417.pdf

From page 56, the gap spec's, how to check, etc. (same as Boscoes earlier post but this pic is from YOUR OWNERS MANUAL)





.

[cpostis]

Your owners manual as a PDF:

http://www.yamaha-motor.com/assets/s...07-03_1417.pdf

From page 56, the gap spec's, how to check, etc. (same as Boscoes earlier post but this pic is from YOUR OWNERS MANUAL)





.

Hold your horses, I just bought your plug and took measurements and pics. Your ground electrodes are semi circular at the tips. IMO, THE BEST WAY TO CHECK GAP IS WITH A 1/16" drill bit between the ground electrodes and center electrode, both vertical. This gap should be
.059-.063".
When I get the time, I'll post the pics.
Better off, change your plugs per Yamaha maintenance schedule in your owners manual.

[pstephens46]

Is this plug designed to prevent detonation?

[boscoe99]

Is this plug designed to prevent detonation?

No, it is not.

[boscoe99]

why not simply look at the Yamaha Marine Technical guides?
they explain both methods with words and pictures.
you can use a .o24" pin vertically between the insulator and the ground electrode or a .062" pin horizontally between the center electrode and the ground electrode tips.

For the owner/end user, which takes precedence? An owner's manual that is provided with each motor or a MTG that is not always available to 99% of the owners?

In the flying world, by law, the operators manual has to be followed by the maintainer. Should it be so in the marine world?

[boscoe99]

I'll call NGK.

rodbolt17, I'm not a marine mechanic and am not aware of the Marine tech guide. I am mechanical and like to do my own stuff as much as I can not because I'm trying to save money but because I like to learn and I have some time. That being said, the first thing I did was directly consult the manual that came with my engine which I thought was the defacto correct place to go for settings and specfics...apparently that is wrong so I will have to start all over again and maybe even call Yamaha but my guess is they will direct me to a dealer and have to do that dance.

I did not expect this to be this much of a can of worms but it is...

You and 99.999% of all Yamaha owners.

Hard to argue with what the anganeers in Japan are saying to do via the owner's manual. The Service Manual, also created in Japan, give the same specification as does the owners manual.

If you call Yamaha USA you may talk to four people and get 8 different answers. What answer would you like to be given sir?

Might it be that there are two different ways to measure the spark plug and still come up with the exact same clearance?

[boscoe99]

Where is our resident measurement speciallist Mr. Fairdeal? I bet if he took some measurements of an HPDI spark plug using his high tech test equipment that we might find there are two ways to measure the gap. With both having the same end result.

If I measure from further away and use a greater clearance, but then measure from closer end using a lesser cleareance, the result might just be the same.

[cpostis]

Image below of what I used to measure the gap:
1/16" drill bit measured with micrometer at .060" actual diameter shaft
.025" feeler wire gauge measured with micrometer at .024" actual




Image of ground electrodes with circular "tips"



Image of .060" drill bit vertical flush to circular ground electrodes and center electrode. Measurement is .060" and within Yamaha specifications



Image of feeler wire gauge .024" vertical flush to circular ground electrode and center porcelain insulator. Measurement is within NGK specifications



Note: I could not see how Yamaha's (Rodbolt's) horizontal method with a pin punch would work as the circular ground electrodes will not allow access to measurement?

This forum would only allow 4 images per post. I will post another with pics of why horizontal method does not work.

[TownsendsFJR1300]

Hold your horses, I just bought your plug and took measurements and pics. Your ground electrodes are semi circular at the tips. IMO, THE BEST WAY TO CHECK GAP IS WITH A 1/16" drill bit between the ground electrodes and center electrode, both vertical. This gap should be
.059-.063".
.

That's what I (and Rodbolt)posted earlier, post #16, to use a wire gauge ESPECIALLY FOR A CURVED ground strap..

It fits in that gap precisely and accurately...

The stock plugs (non iridium NGK's) for my motorcycle have the same style ground straps as these plugs in question.. And gapped exactly the same...

[cpostis]

Drill bit placed horizontally. Circular ground electrodes do not allow proper measurement.




Wire feeler gauge placed horizontally. Circular ground electrodes do not allow proper measurement as well.

[cpostis]

That's what I (and Rodbolt)posted earlier, post #16, to use a wire gauge ESPECIALLY FOR A CURVED ground strap..

It fits in that gap precisely and accurately...

The stock plugs (non iridium NGK's) for my motorcycle have the same style ground straps as these plugs in question.. And gapped exactly the same...

Not to argue, but Rodbolt's post #8 says otherwise (horizontal to vertical), although he may have meant different. Your post says nothing about horizontal or vertical.

Factcheck, are you guys telling the truth?

Just posting pics to clarify for the OP and others interested.

Now I'll go get a beer or two!

[boscoe99]

So why are the side ground electrodes circular at the tip? NGK does not say in this document. Which is a pretty good read. Thought plugs were simple? Apparently not.

https://www.ngk.com/glossary/8/spark-plug/M