Spark Plug thread length

My derbi kits head has a deeper plug hole than the stock head. Will running a regular plug cause problems. It seems like it would cause an uneven burn. Do the plugs come in both versions of say a BH7S?

Re: Spark Plug thread length

You need to check a derbi manual to see what plugs they recommend, and then compare thread length to other plugs. I'm sure there is some sort of something in the plug name/number that indicates thread depth, but fuck if I know what it is. Just figure out what you need, or get ahold of a plug the manual recommends, and then take it into the auto parts store to get plugs that correspond.

Re: Spark Plug thread length

b7es is the longer ones. i think thats what you need.

Re: Spark Plug thread length

Yep you need an es plug. Pat at 1977 was running an hs plug in his and after relizing it needed an es he said it picked up some low end power ( higher compression). Horray free performance gains.

Re: Spark Plug thread length

) Cupermcnewbster ( /

B7 or B8ES is your plug. They give you a little power boost as paz says coming from an HS

Re: Spark Plug thread length

Thanks I had a long bosch plug and threw that in to test it out. I'll get the B7ES tomorrow.

Want to post in this forum? We'd love to have you join the discussion, but first:

Login or Create Account