Topic: NGK Plugs for 73 CB750K Anyone tried DP7FA9

[mrmach5]

My 73 CB750K has a habit of fouling plugs in a short period of time,
compression 135 -145
stock airbox
Busso 4 into 4 340 reproduction exhaust
Valves adjusted
Timing on spot
Sea level
105 mains 40 pilots needles 3rd grove
have not test driven yet but recently drilled the top eight emulsifier tube holes to 0.039" and installed 35 pilot jets .
Has anyone tried NGK DP7FA9 plugs in these bikes ? Looks to have about a 1mm projected tip.
Their description.
Designed to operate over a much wider heat range than ordinary plugs. Heat Range: 7
Resists carbon buildup and pre-ignition
High alumina ceramics for better heat transfer and electrical insulation
Solid copper core and nickel tipped electrode provide a longer plus life

[Deltarider]

Do you mean DP7EA-9?
See: https://www.ngk.com/compareproducts
I see no objection but I leave it to the experts here to judge whether the electrodes will be too close to the piston. Gap is a bit wide which in theory may shorten the burn time somewhat.
I have no idea what you expect of drilling the top eight emulsifier tube holes to 0.039.

[mrmach5]

Wow ,
Sorry,,, my mistake. Yes NGK DP7EA 9 

[Don R]

 I put them in a big bore engine and the pistons closed the gaps, but it has high compression pistons.

[HondaMan]

I have no idea what you expect of drilling the top eight emulsifier tube holes to 0.039.

This is commonly done in the 657A/B carbs of the 750 to reduce plug fouling in city traffic situations when running too much octane (or today, when using ethanol-laced fuels). It also helps blend the transition from 1/2 throttle upward, where the wasp-waist in those carbs causes a 'flat spot' in the throttle response right around 70 MPH-75 MPH in the K2/3 bikes in top gear, in particular.

[dave500]

check your plug caps resistance.