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Discussion Starter · #1 ·
Napa guy told me to gap my gl650I spark plugs at .35. It doesn't sound right to me. I was thinking .28. If your reading this and know what to gap them at would you please let me know.
 

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I found THIS with a search. Odd that different plugs list different gaps.



Also noted that the listed plugs seem to be for differing size engines. The two for 650's list 0.020" and 0.028".



Just noticed that the plugs listed are iridium (which I use). I suppose that standard plugs would gap the same, certainly not more (larger gap).
 

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I thought they came pre gapped.
 

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I know you said GL650... but when I had called my Honda dealer they said THEIR plugs come pre gapped- after some pressing to get the info just so I have it, he told me for my GL500 it was .64



you guys have .020 and .028, and mine is .64???
 

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I know you said GL650... but when I had called my Honda dealer they said THEIR plugs come pre gapped- after some pressing to get the info just so I have it, he told me for my GL500 it was .64



you guys have .020 and .028, and mine is .64???


Even if they meant 0.064 they're way off or quoted metric as 0.64 would equal a bit less than 0.026"



The service manuals should be on the dropio website.



0.02 sounds too small for anything, 0.026 - 0.028 should be the right range.
 

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Napa guy told me to gap my gl650I spark plugs at .35. It doesn't sound right to me. I was thinking .28. If your reading this and know what to gap them at would you please let me know.




My Silverwing GL650 Manual says the spark plug gap is 0.031" to 0.035"

And, I have always checked and found the NGK plug gap from the box to be right in the range.

Regards,
 

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Discussion Starter · #8 ·
I'll go check the manual in the quick reference section.



I'd like to see what Larry, Sam I am, Gray Wolf, Abes, David in Wisconsin, Sly Fox, have to say.
 

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According to the Owners manual that came with my '82 GL500I it says:



Spark Plug Gap: 0.6-0.7mm (0.24-0.28 in)



The FSM (Factory Service Manual) for the CX500 on the Drop I.O. site says the exact same specs.



And finally my Clymers manual for Honda CX & GL500/650 Twins 1978-1983 also says .024-.028 in (0.6-0.7mm)



Greg
 

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Discussion Starter · #10 ·
THank you Graywolf. I'm backing mine down to those specs. Maybe it will sound a wee different.
 

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I found THIS with a search. Odd that different plugs list different gaps.



Also noted that the listed plugs seem to be for differing size engines. The two for 650's list 0.020" and 0.028".



Just noticed that the plugs listed are iridium (which I use). I suppose that standard plugs would gap the same, certainly not more (larger gap).


I went and looked at the site in the link above.



It looks like they are suggesting the larger (.032-.035)gap for larger (over 1000cc's) engines.

The plug for 650 cc's on this web site does show a gap of 0.028"



Greg
 

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Most plugs are pre gapped, doesn't hurt to check 'em.



Running on Metric system over here, so plugs are always set at 0.6mm. If having stator issues, reset the gaps to 0.5mm, will get you home OK. (Thanks Glen)



Also, if the plugs you remove are OK, keep them in your tool kit. You know they work.

Have had a bad plug, straight out the box. Took us hours to fault find.
 

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The manual spark gap specifications are referenced on the following pages:

Section 1-3,

Section 3-7,

Section 17-1,

Section 23-5, and

Section 24-4.

0.024-0.028 is written for Section 1-3 and 3-7

0.02-0.03 is written for Section 17-1

0.024-0.028 is written for Section 23-5

and

0.031-0.035 is written for Section 24-4

Since this thread got started with a question about the GL650 and the Addendum portion of the manual is devoted exclusively to the GL650 (Section 24-4) it follows that the spark gap is wider for the GL650 than the GL500.

I've never owned a GL500, so I cannot compare results of the spark plug changeouts, but for the riding I've done I have always inspected the condition of my plugs when doing the maintenance and found them to appear to be textbook Tan-colored. Plus my gas mileage is consistently in the 50+ mpg. So, it appears the factory intended the wider spark gap for the GL650.

Regards,
 

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I had 4 champion brand spark plugs all not fire straight out of the box. Took me days to figure it out. Being young and inexperienced I thought I'd done something stupid until I put the old plugs back in and it fired right up. That was 30 odd years ago and have never bought a champion plug since.
 

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Discussion Starter · #15 ·
So many opinions of the spark plug gap. I believe the section wingsofthe101 is probably correct.



So which leads me to my next question. Supposedly spark plug gap affects timing. If this is true then a wider gap would either advance or retard the timing a wee bit. Anybody care to weigh in on this one?
 

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The points gap in the older systems affected timing, larger gap sparked earlier. Don't know about plug gap. Think this has more to do with the ignition firing power and compression ratio of specific motors.... but I have been wrong before.
 

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Discussion Starter · #17 ·
The points gap in the older systems affected timing, larger gap sparked earlier. Don't know about plug gap. Think this has more to do with the firing power and compression ratio of specific motors.... but I have been wrong before



Exactly what I was referring to. However I have read in the same manuals that the gap has some affect to timing. But that is why I brought it up. Sounds like hog wash to me. But I don't know.
 

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Shouldn't affect timing at all. Points, timing chain slack etc can, but all the plug does is fire. Apparently the spark jumps across carbon atoms, so gaps are different if you run different fuels, LPG, Avgas, premium etc.



'course I could be wrong also....happens all the time.
 
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