Topic: Cb450 the next hotter plug

[kerryb]

We’re trying to tune a cb450 motor in a custom bobber. So far we have fouled plugs on this setup  see pic
  With k&n oval pods, we raised the clip one notch from center (lowered needle), and it fouled the pugs in a couple short trips.  So after a little discussion we are seeking the next hotter plug from ngk DPR9EA    9  my  local chopper shop is recommending  D0R8EA, would you agree?
   Carbs are Mikuni 32 mm, exhaust is very low restriction,

[seanbarney41]

The P in DPR is for "projected" as in projected tip.  So I don't think there is any such thing as a DOR ngk and if there is, it is not because of the heat range.  So yeah, I believe you are correct to look for the DPR9EA.  What are you using for fuel?

Everyone always says not to use heat range to correct a fueling problem but I have done that in the past, at least to keep it running long enough to assess performance.

Amazingly enough, I recently installed a set of VM32 Mikuni's on a CL450 for a customer.  The throttle shafts on his stock Keihins had worn to the point that they would no longer seal.  We used a custom fit for the 450 kit from Niche Cycle.  Fit was very nice and jetting was very close right out of the box, but I have no idea what settings were in there.

[kerryb]

The P in DPR is for "projected" as in projected tip.  So I don't think there is any such thing as a DOR ngk and if there is, it is not because of the heat range.  So yeah, I believe you are correct to look for the DPR9EA.  What are you using for fuel?

Everyone always says not to use heat range to correct a fueling problem but I have done that in the past, at least to keep it running long enough to assess performance.

Amazingly enough, I recently installed a set of VM32 Mikuni's on a CL450 for a customer.  The throttle shafts on his stock Keihins had worn to the point that they would no longer seal.  We used a custom fit for the 450 kit from Niche Cycle.  Fit was very nice and jetting was very close right out of the box, but I have no idea
what settings were in there.

I,m confused, DPR9EA  is what we have now, what would be an appropriate hotter plug?

[scottly]

With NGK, the smaller the number, the hotter the plug, so an 8 is hotter than a 9, and a 7 is hotter than an 8.

[seanbarney41]

Ok...stock plug for 450 should be D8EA I believe (please look it up to confirm)  That plug is discontinued.  NGK wants you to use DR8EA in place of that.  I don't know why you are getting that projected tip suffix in there?  Maybe that is all NGK offers in that size and range?  It is going to move the spark farther out into the combustion chamber though, no idea if you really want to do that or not. 

The number designates heat range.  So your 9 is one range different than an 8 that is stock for the bike and now that I think about it, (please check this too somewhere authoritative, like NGK?) 9 is cooler than 8.  If you want to go hotter you need a 7.

...or Scottly, confirms this

[CycleRanger]

You ought to ask the folks over at https://www.vintagehondatwins.com/forums/

Lots of CB450/Mikuni experience over there.
Also, whatever plugs you end up with make sure you don't double up the resistance by combining resistor plugs (DR8EA) with resistor caps.

[MauiK3]

Is it just me? If the engine in question is a CB450, the second photo does not look like the DOHC twin 450, is there another 450 I’m unaware of?

[seanbarney41]

No, you are right.  That is a later 1980's 450 twin.  I believe it is sohc.  Forgot it's designation but it may be based on bikes like Nighthawk 450.  I know nothing about these.

Pretty sure that picture was not there when I originally posted.  No idea how it appeared later.