Spark plugs ...can I use a little hotter plug? Maybe 9's instead of 8's??

1982 KZ1100 Spectre spark plugs ...can I use a little hotter plug? Maybe 9's instead of 8's??

If you just put around town they probably would be ok but out pounding the pavement on the interstate may burn a hole in the top of the piston. Don't ask how I know.

What brand are you using.
Generally 9's run colder than 8's.
I run 9's in all my Zeds.
A hotter plug than an 8 would be a 7 .

zed1015 wrote: What brand are you using.
Generally 9's run colder than 8's.
I run 9's in all my Zeds.
A hotter plug than an 8 would be a 7 .

True for NGK, but some brands (eg. Autolite) have the heat ranges reversed.

For them, a 9 would be hotter than an 8. Dunno why anyone would use Autolite in anything tbh haha

blackumi wrote:

zed1015 wrote: What brand are you using.
Generally 9's run colder than 8's.
I run 9's in all my Zeds.
A hotter plug than an 8 would be a 7 .

True for NGK, but some brands (eg. Autolite) have the heat ranges reversed.

For them, a 9 would be hotter than an 8. Dunno why anyone would use Autolite in anything tbh haha

Yes! That's why I wrote " Generally".
Just in case he was using something other than the normal NGK or Denso such as Bosch or Champion.

Barry2 wrote: If you just put around town they probably would be ok but out pounding the pavement on the interstate may burn a hole in the top of the piston. Don't ask how I know.

Pretty sure using a hotter plug won't cause and increase in combustion temperature. It's about plug life; the right temperature plug is not so hot that it melts the electrode and not so cold that it fouls it. The only reason to go hotter is if you are fouling the plugs you are using.

zed1015 wrote:

blackumi wrote:

zed1015 wrote: What brand are you using.
Generally 9's run colder than 8's.
I run 9's in all my Zeds.
A hotter plug than an 8 would be a 7 .

True for NGK, but some brands (eg. Autolite) have the heat ranges reversed.

For them, a 9 would be hotter than an 8. Dunno why anyone would use Autolite in anything tbh haha

Yes! That's why I wrote " Generally".
Just in case he was using something other than the normal NGK or Denso such as Bosch or Champion.

ya know reading isn't my strong suit

zed1015 wrote: What brand are you using.
Generally 9's run colder than 8's.
I run 9's in all my Zeds.
A hotter plug than an 8 would be a 7 .

Was looking at the spark plug thread. Realized we run NGK '9' in the old Hemi Blown Gasser. Burning Methanol, 1500 HP engine.
I started saving the NGK plugs. Run them about 15-20 1/8 mile passes.
Not much difference, 2 Hemi heads! KZ1000 & 1955 Chrysler Hemi 354 Little bit bigger on the valves
Plus I used Autolite 403 plugs. Awhile back "Rock Auto dot com" had closeout sale on the Autolites 403's for 97 cents a piece.

I'd never recommend going the other way either..... one step cooler (unless your beating on it all the time maybe) .... a few bike shops talked me into it and although they didn't fowl I needed to go through a few gears to clean em out before it ran best.

Had it happen to a friends bike and I was the one that fixed it. Had a hole about the size of a pencil right under the plug.

The real question is "what are your trying to accomplish by running a hotter plug?". A hotter plug does not dissipate tip heat as well as a colder. However, a hotter tip does not mean increased spark or performance. If you're experiencing excessive carbon build up, the plug may not be reaching a high enough temperature to burn off deposits or clean itself. Typically this would be caused by cold temperatures (ambient), extended periods of slow operation, rich fuel mixture or lack of ignition advance. Carbon plug fouling is a symptom, but not necessarily the problem. Going to a hotter plug may solve fouling issue, but too high tip temperature can also cause per-ignition and detonation. Given the choice of having to clean fouled plugs or rebuild a destroyed engine, I'd err towards a cold plug. Check that your ignition is advancing properly and your carbs are jetted correctly before you start messing with plug heat ranges.