Air cooled RD spark plugs

[2t Fan]

which all air-cooled RD350.s came out with B8ES plug. European 522/521.s use them I have heard of. I understand that most US RD350.s use B8HS plugs. Did 1975 bikes use B8ES?

[SoCal250]

All US-model 1973-75 RD250/RD350 use B8HS (5510) 1/2" reach plugs.

The 1975 521 RD350 & 522 RD250 in Europe (and maybe some other regions) use a B8ES (2411) 3/4" reach plug. If the bike is equipped with 521-11111-00 RD350 heads or the 522-11111-00 RD250 heads then it requires the longer plugs.

[2t Fan]

thanks so much