colder plugs

[odieoh24]

bike was running a little rough on initial take off, even after warming it up for 8-10 min. started with the plugs and was unable to obtain a set of new iridiums, or the stock dpr8ea-9. i was able to get a set of dpr7ea-9's. installed them and the bike has run better than it did prior to the problem. am i gonna screw stuff up by running a plug one size colder than stock? the bike sure seems to like it!

thanks odieoh24

 

[hubeerjw]

Aren't the 7's actually hotter? I thought I was using DPR9-EA9's as a colder plug... I'll look it up and let you know.

 

[hubeerjw]

I just found this on NGK's website:

Heat range

The term spark plug heat range refers to the speed with which the plug can transfer heat from the combustion chamber to the engine head. Whether the plug is to be installed in a boat, lawnmower or racecar, it has been found the optimum combustion chamber temperature for gasoline engines is between 500?C?850?C. When it is within that range it is cool enough to avoid pre-ignition and plug tip overheating (which can cause engine damage), while still hot enough to burn off combustion deposits which cause fouling.

The spark plug can help maintain the optimum combustion chamber temperature. The primary method used to do this is by altering the internal length of the core nose, in addition, the alloy compositions in the electrodes can be changed. This means you may not be able to visually tell a difference between heat ranges. When a spark plug is referred to as a ?cold plug?, it is one that transfers heat rapidly from the firing tip into the engine head, which keeps the firing tip cooler. A ?hot plug? has a much slower rate of heat transfer, which keeps the firing tip hotter.

An unaltered engine will run within the optimum operating range straight from the manufacturer, but if you make modifications such as a turbo, supercharger, increase compression, timing changes, use of alternate racing fuels, or sustained use of nitrous oxide, these can alter the plug tip temperature and may necessitate a colder plug. A rule of thumb is, one heat range colder per modification or one heat range colder for every 75?100hp you increase. In identical spark plug types, the difference from one full heat range to the next is the ability to remove 70?C to 100?C from the combustion chamber.

The heat range numbers used by spark plug manufacturers are not universal, by that we mean, a 10 heat range in Champion is not the same as a 10 heat range in NGK nor the same in Autolite. Some manufacturers numbering systems are opposite the other, for domestic manufacturers (Champion, Autolite, Splitfire), the higher the number, the hotter the plug. For Japanese manufacturers (NGK, Denso), the higher the number, the colder the plug.

Do not make spark plug changes at the same time as another engine modification such as injection, carburetion or timing changes as in the event of poor results, it can lead to misleading and inaccurate conclusions (an exception would be when the alternate plugs came as part of a single precalibrated upgrade kit). When making spark plug heat range changes, it is better to err on the side of too cold a plug. The worst thing that can happen from too cold a plug is a fouled spark plug, too hot a spark plug can cause severe engine damage

 

[odieoh24]

so should i pull the ones i have in there and try the 9's? bike did run fine prior to the plug issue. everything has cleared up. i'll pull the 7's and make sure i tell the guy at auto parts plus he's an idiot. i shoulda done the research myself. thanks hubeer

later odieoh24

 

[526 turbo]

hi guys, wanted to know which plugs u recommend also. have a 19913 with 1986 carbs, with F1 slip ons, bike pops. took plugs out and they are white almost no burn coloring on them. they r stock plugs, do I need colder ones maybe. thx guys:ummm:

 

[naughtyG]

hi guys, wanted to know which plugs u recommend also. have a 19913 with 1986 carbs, with F1 slip ons, bike pops. took plugs out and they are white almost no burn coloring on them. they r stock plugs, do I need colder ones maybe. thx guys:ummm:

It sounds more like you're running a bit lean. I would first try giving all 4 AF screws half a turn anti-clockwise, and if that doesn't help then look at your jetting.

How does the bike run?