Spark Plug Differences

[mcgovern61]

I pulled my spark plugs yesterday and they were in real good condition; slightly tan, no worn electrode, still gapped at .24 inches. I decided that since they had 11,000 miles on them I would replace them anyway (cheap enough). Checking the manual for yucks, the plug recommended for the '82 engine is NGK DPR8EA. The Clymer manual lists the '80-'81 as using the NGK DP8EA which are the plugs I had in the bike. They were new for the last 100 miles on put on the '81 engine so I just transferred them to the '83 engine when I swapped them out. My question is, should I be using the NGK DPR8EA plugs? At the parts store, he brought both plugs out and the NGK DPR8EA is a few MM longer than the NGK DP8EA.

With the interference engine, I didn't want to chance a longer plug! But then again, they are recommended for the '82? Got me to thinking, should I change out the plugs? What would be the advantage (if any)?

Before anyone replies, please know this:

'83 engine in an '82 frame with '81 carbs, '81 wiring harness, '81 coils, no resister in the wires like original (that I know off.....they were changed to Grey Dyna Spark Plug Wires).

 

[dan filipi]

I would go with the 83 plug.
Reason being is the ignition is essentially the same and reach is more important here.

 

[backlander]

My references show that the D8EA is the plug needed for 80-81 model. The two plugs you have listed are for 82-83 model, the DP8EA-9 and the DPR8EA-9. The only difference in those two is the DPR is a resistor plug. All three plugs have the same reach, 19mm and are the same heat range of 8, according to NGK's website specs on the three plugs.

 

[AApple]

backlander » Sat Jul 27, 2013 7:04 pm[/url]":3lwa3qlr]
The only difference in those two is the DPR is a resistor plug.

+1 :yes:

 

[mcgovern61]

backlander » Sat Jul 27, 2013 7:04 pm[/url]":21pgn6zb]
My references show that the D8EA is the plug needed for 80-81 model. The two plugs you have listed are for 82-83 model, the DP8EA-9 and the DPR8EA-9. The only difference in those two is the DPR is a resistor plug. All three plugs have the same reach, 19mm and are the same heat range of 8, according to NGK's website specs on the three plugs.

Specs might say they are the same, but when we put the plugs side by side, there are more threads on the DPR8EA-9. I am using the D8EA plugs, but it is an '83 engine. Is it the other ignition parts that take preference ('81 wire harness, '81 coils)?

What does the resistor plug do? How is it different?

 

[toytender01]

Resister Plugs areused for nouse suppressiom for radios

 

[ekvh]

Just emailed NGK last week about how much more projection it has. They emailed back that the dpr8ea is 0.081" longer than d8ea. The r is for resistor and shouldn't affect piston clearance. I am toying with putting the dpr8ea in the 1000.

 

[mcgovern61]

toytender01 » Sat Jul 27, 2013 10:01 pm[/url]":33p9cju1]
Resister Plugs areused for nouse suppressiom for radios

Is that in combination with the resistor in the plug cap? I am using the Dyna wires instead of OEM without the resistor caps on the plug wires.

Just emailed NGK last week about how much more projection it has. They emailed back that the dpr8ea is 0.081" longer than d8ea. The r is for resistor and shouldn't affect piston clearance. I am toying with putting the dpr8ea in the 1000.

Good thing to know that my eyes did not fail me on that one! :hihihi: If it does not affect piston clearance, than will it be advantageous to have plugs that reach deeper?

 

[ekvh]

Honda decided that with numerous others as near as I can tell around 1983. It has been found there is an ideal spot for flame propagation and hence performance. I am just wondering on the 75-82's. I know the 75-79 pistons were more hemi shaped than the 1200, but the 1200 came up proud of the block where the early models did not. I may give it a try. I think it will clear. Why not right now? Okay, I will. I will watch the plugs regularly for evidence of too warm, or heaven forbid aluminum on them.

 

[ekvh]

I did it for about twenty miles of city driving. Seemed a little worse than iridium at idle, but seemed better at cruise. All seat of the pants feeling. Plug gap is 0.035 and probably too much. I'm going to run a tank through it and see what the mileage does. I will pull them in the morning. I'm away for a few days.

 

[ekvh]

They were pretty clean and maybe too white. I went another 15 miles last night. At cruise it runs great. I am watching my mileage for this one. I'll take another look at them this morning.