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Plug temperature question

  • Thread starter Thread starter GS750GUY
  • Start date Start date
G

GS750GUY

Guest
I notice the manual for my 78 GS750EC says to use NGK B-8ES spark plugs and I find the prior owner has been using NGK G-7ES plugs.
Can someone out there tell me if the B-8ES plugs are a cooler plug? Did the prior owner possibly switch up one notch to a hotter plug?
If so should I stay with the hotter plug or go back to using the manual recommended B-8ES?
I think I read somewhere where the factory tends to determine plug choice based on the bike being used under its worst conditions.
The prior owner, like myself, is a very conservitive rider rarely running the engine at its top end capabilities and spent most of the time just cruising aroud at in-town speeds. Could it be the prior owner, due to his riding habits was possibly constantly fowling plugs so as a result his mechanic possibly switched to a hotter plug?
I appreciate the wisdom and advice of GS plug geru's out there.
GS750GUY
 
GS750GUY said:
Could it be the prior owner, due to his riding habits was possibly constantly fowling plugs so as a result his mechanic possibly switched to a hotter plug?
Click to expand...

my thoughts exactly

my plugs tend to foul if i stay too long at under 3000rpm
yes, the carbs are clean etc etc

but i sort that out by not riding below the 4k rpm :D
 
GS750GUY said:
I notice the manual for my 78 GS750EC says to use NGK B-8ES spark plugs and I find the prior owner has been using NGK G-7ES plugs.
Can someone out there tell me if the B-8ES plugs are a cooler plug? Did the prior owner possibly switch up one notch to a hotter plug?
If so should I stay with the hotter plug or go back to using the manual recommended B-8ES?
I think I read somewhere where the factory tends to determine plug choice based on the bike being used under its worst conditions.
The prior owner, like myself, is a very conservitive rider rarely running the engine at its top end capabilities and spent most of the time just cruising aroud at in-town speeds. Could it be the prior owner, due to his riding habits was possibly constantly fowling plugs so as a result his mechanic possibly switched to a hotter plug?
I appreciate the wisdom and advice of GS plug geru's out there.
GS750GUY
Click to expand...

Or maybe they were out of B8ES, someone told him it would go faster, or maybe he was riding in the Yukon in February.
I'd try the B8ES if all else is original and see how it works.
 
Many times the plugs are changed to hotter plugs because they are fouling. Rather than fix the cause of the fouling, they just put in hotter plugs. If the bike is jetted correctly, you should get along fine with the B8ES.

By they way, riders don't come much more conservative than my wife.
Here is a shot of two spark plugs. One of them, TheCafeKid has just removed from his (former) GS1100G after about 5,000 miles. The other is from my wife's 850L and it has about 15,000 miles on it.
Which one is which? :-k

IMG_7651.jpg


By the way, my wife's plug went back into her bike.
TCK's plugs got rescued out of the trash and got put into my parts box as spares.
If he keeps changing them at 5,000 mile intervals, I will have free plugs for life. :dancing:
 
Steve said:
Many times the plugs are changed to hotter plugs because they are fouling. Rather than fix the cause of the fouling, they just put in hotter plugs. If the bike is jetted correctly, you should get along fine with the B8ES.

By they way, riders don't come much more conservative than my wife.
Here is a shot of two spark plugs. One of them, TheCafeKid has just removed from his (former) GS1100G after about 5,000 miles. The other is from my wife's 850L and it has about 15,000 miles on it.
Which one is which? :-k

IMG_7651.jpg


By the way, my wife's plug went back into her bike.
TCK's plugs got rescued out of the trash and got put into my parts box as spares.
If he keeps changing them at 5,000 mile intervals, I will have free plugs for life. :dancing:
Click to expand...
And I will....so just keep stockin up my friend :P
 
Run the B8ES, if you see there is a problem, probably won't be, then start looking for the cause & remedy.
 
I'm guessing your wife's plug is the one on the right.
GS750GUY
 
Actually, If i remember correctly, the one on the LEFT is his wifes...the right one is one of my throwaways..
 
Ok, I'll be the one to ask. Why did you change out perfectly good plugs ?
 
GS750GUY said:
I'm guessing your wife's plug is the one on the right.
Click to expand...
Sorry, you lose. :oops:


TheCafeKid said:
Actually, If i remember correctly, the one on the LEFT is his wifes...the right one is one of my throwaways..
Click to expand...
Yes, you remember correctly. :D


don_gibb6512 said:
Ok, I'll be the one to ask. Why did you change out perfectly good plugs ?
Click to expand...
I asked the same thing as he was tossing them into the trash can. He said something about keeping the fresh. That's when I pulled my wife's plug for comparison.

I have always changed plugs based on appearance and measurement, not time or miles. Depending on the bike/car/van they were in, the mileage changed, but they usually go considerably longer than most people think. When the new plugs are installed, if there is a gas mileage improvement, it's too small for me to notice. Wife's bike is approaching 17,000 miles on her plugs. I have yet to change the plugs in my Wing since I got it. No idea when the previous owner changed the plugs, but I got the bike with 91,000 miles on it, it now has over 136,000. I change the plugs in my vans every 100,000 miles only because they are platinum-tipped and I have to remove the front passenger seat to get to them.

.
 
don_gibb6512 said:
Ok, I'll be the one to ask. Why did you change out perfectly good plugs ?
Click to expand...
It wasnt perfectly good. It had over 5k miles on it. They were in the bike when I bought it, no idea how long theyd been in there, so I put fresh ones in. I was going on a long trip, and covered everything I could think of. And Yes, i change my plugs (would normally change at 7-10k miles, but these were questionable) and oil (EVERY 2k miles or less) at short intervals. Some call it paranoia, I call it preventative maintanence. :p
 
B6ES-- north pole-- too hot for most of us.
B7ES hot-- winter time
B8ES cooler general use
B9ES colder-- hi performance or summer time riding
B10ES super cold -- death valley desert racing ultra high performance engine lots of timing advance


but a hotter plug will damage piston crown and top ring land by helping detonation and pre-ignition during improper combustion (carbon build up, bad jetting,wrong timing all factor in)

when it runs bad... bad things happen to the parts inside the engine
 
Some call it preventative maintenance, some call it paranoia, I say it's doing what suits you.
 
trippivot said:
B6ES-- north pole-- too hot for most of us.
B7ES hot-- winter time
B8ES cooler general use
B9ES colder-- hi performance or summer time riding
B10ES super cold -- death valley desert racing ultra high performance engine lots of timing advance
Click to expand...
Just please remember:
The 'temperature' of the plug does not control the temperature of the combustion. Putting in a 'hotter' plug does not make the engine run hotter.

The 'temperature' of the plug is a measure of its ability to dissipate heat from combustion. A 'hotter' plug has a longer heat sink path, so it stays warmer. Hopefully, warmer enough to keep it clean. A 'colder' plug has a rather short heat sink path, so it tends to run cooler. This is desireable when you are running the engine hard, like in racing conditions.

When all is said and done, the actual temperature at the tip of the plug should remain in a range that is warm enough to keep deposits from forming, but cool enough to not light the mixture before the spark happens. And, this temperature will be about the same from one heat range of plug to the next, if they are used as intended. That is, the tip temperature of the B7ES that you put in for your low-speed commute should be about the same as the tip temperature of the B9ES that you put in for racing on the weekend.

But, rather than use hotter plugs to burn off deposits, why not fix what is putting the deposits there in the first place, and run standard plugs?


(No, I did not stay in a Holiday Inn Express last night. I actually attended a seminar several years ago that was put on by Champion Plugs. VERY informative.)

.
 
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