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Just wondering what kind of spark plugs you use i seen some manuals say b8es and some say b7es. My bike seems to run good with both but i don't know what one runs it better. I do have pod filters but am unsure what jets are in it, it seems like i change the plugs more than i should because they are getting black like carbon fouled or something.

PLEASE add your bike's year and exact model to your signature line. Doing so will help you get accurate answers. Ed

OEM manual is the bible.

Both spark plugs would work well. NGK site explains the numbers. Basically the B7ES is hotter thant the B8ES, meaning it transfers less heat. Considering your description indicates you are running too rich, the B7ES is better until you figure out a better setting.

...your problem does not seem to be spark plugs, but rather deviating from stock, with the so called 'performance mods' which is like opening a pandora box.

hugo wrote: Both spark plugs would work well. NGK site explains the numbers. Basically the B7ES is hotter thant the B8ES, meaning it transfers less heat. Considering your description indicates you are running too rich, the B7ES is better until you figure out a better setting.

...your problem does not seem to be spark plugs, but rather deviating from stock, with the so called 'performance mods' which is like opening a pandora box.

Huh??? The correct spark plug would depend entirely on what model bike it is to be used in; they do not all use the same plugs. Without knowing what motorcycle he's talking about it is impossible to recommend the correct spark plug. Does he have a KZ200, GpZ550, GpZ900, KZ1300 or what other model of the many possible models? Ed

Additionally the workshop manuals did get updates and amendments issued by KHI. For example the original KHI manuals for 650B's specified 8's and was later revised to 7's.
But either way use Denso equivalents, they seem to be much more sympathetic to "misuse"

Warren3200gt wrote: Additionally the workshop manuals did get updates and amendments issued by KHI. For example the original KHI manuals for 650B's specified 8's and was later revised to 7's.
But either way use Denso equivalents, they seem to be much more sympathetic to "misuse"

Exactly! The 8's may have worked in the KZ650 on the race track, but didn't work well at all on the street even if the bike was ridden quite hard. Ed

Thanks guys, i really don't know much about these motors as i just purchased it but funny its on a suzuki LT500r quad frame! Converted to 520 chain

I don't know who told you that is a 1979 motor, but they were wrong. That is a 1977 KZ650 motor. You should use either NGK B7ES plugs or (Denso / Nippondenso) ND W22ES-U plugs. Personally I have found the ND W22ES-U plugs to work a bit better in my 1977 KZ650 than the NGK B7ES plugs. Ed

Thank you for the info. i'm just going by what the engine says, its stamped KZ650B3 which i thought was a 1979 but could be wrong, you guys know more than i do about these.

Where is the "KZ650B3" number stamped? The actual engine serial number should be stamped next to the oil filler cap, and it should not have KZ650B3 or any other specific KZ650 model number stamped there. It should be stamped with KZ650BE024200 where those last 6 digits represent the actual engine serial number. If you post that number we should be able to verify the engine's year beyond any doubt. The reason I said it is a 1977 KZ650 engine is the fact that it has the 3 allen bolts in the generator cover. No other year KZ650 had those bolts because that generator was only used in 1977. After 1977 the generator cover had no allen bolts. Below is a photo of the generator cover on my 1977 KZ650 and a 1978 cover. Ed

1977 COVER


1978 COVER

I will get a pic of the engine serial number this weekend. thanks for your help this is helping me out a lot