Topic: Will hotter plugs help or hinder CB750 w/ 4-2-1?

[SpacemanSpiff]

'74 CB750,  First bike project, 14 months in, running but not quite road worthy.

I have a 4-2-1 older Yoshi exhaust, and replacing stock carb jets today and I want to replace my plugs, but will hotter D7EA run better than standard D8ea? thanks.

[flybox1]

are you changing size to accommodate exhaust or intake changes or just swapping out because the new ones are shiny?
run the proper D8EA plugs, and get the mixture right.

[SpacemanSpiff]

I'm jetting to 120 to accomodate 4-2-1 exhaust, and existing plugs are old, unfouled and unused D8EA w/ 105 main carb jets and idles beautifully BUT producing severe lack of power in gear, low-through to mid-range. Had a set of 110 jets, swapped them out (carbs are recently cleaned, and synced) and it ran better, but still loss of power, hence the 120 jets i'm testing tonight, got em out of the mailbox minutes ago.

So I was thinking of buying a new set of plugs to cover all my bases, in case the old ones are clean but tricking me into thinking they're sparking 100% of the time. And if I'm buying new plugs, do I want hotter ones to accommodate new jets or is that totally irrelevant?

I'm also investing in an oil cooler soon...

[flybox1]

I'm jetting to 120 to accomodate 4-2-1 exhaust, and existing plugs are old, unfouled and unused D8EA w/ 105 main carb jets and idles beautifully BUT producing severe lack of power in gear, low-through to mid-range. Had a set of 110 jets, swapped them out (carbs are recently cleaned, and synced) and it ran better, but still loss of power, hence the 120 jets i'm testing tonight, got em out of the mailbox minutes ago. But we all know main jets dont control low through mid range ....so why not make adjustments there first?       You have mixture screws, pilot jets, and needle clip positions to adjust specifically for what you described....  Your plugs arent the problem, your IDLE -> 2/3 throttle position carb jetting is.

So I was thinking of buying a new set of plugs to cover all my bases, in case the old ones are clean but tricking me into thinking they're sparking 100% of the time. And if I'm buying new plugs, do I want hotter ones to accommodate new jets or is that totally irrelevant? 

I'm also investing in an oil cooler soon...

as i said above, D8EA plugs are correct. 

[flybox1]

you might help us help you by including the pertinent info, like:
carb model
current jet sizes(stock or aftermarket),
needle clip positions
mixture screw settings
intake type (be specific)

[SpacemanSpiff]

Making notes from your post and coming back here later after shop time

[Mr Freeze]

You could also try the Denso X24ES-U plug. I've been running those for the past year and they'be been really good. Haven't pulled one in a while to check them out because I've been riding almost every day.

[PeWe]

Warmer plugs will not help when carbs are wrong jetted.
My carbs were too lean whith bad throttle response. Standard needles? Aftermarket might need other setting according to other threads here.
Not tuned engine, std needle setting (middle notch), main around 115 with std airfilter box. I used std pilots (40).
Ignition OK? Too late will give bad response, too early pinging. (too lean will help pinging to occur as well).

I use NGK D8EA. Irridium plugs did not work better in my tuned engine. Denso std plug mentioned will also work.