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‘78 CX500 spark plug question

2K views 16 replies 10 participants last post by  bobnstuff 
#1 ·
Okay. I’ll try to keep it short.

my new (to me) cx500 seems to lack some pep and seems to run better on the left cylinder than the right. I swapped the spark plugs after some tinkering with other things to see if there’s a difference. Seemed to help some BUT when I pull the plugs theyre D7EA NOT D8EA, which from what I e read is stock. Would this cause issues? I am planning on replacing them as theyre cheap and if it helps at all I’d be happy but want to ensure I use proper parts.
Any help or guidance is appreciated.
 
#2 ·
The FSM says D8EA for all CX500 models with CDI.

As you can see from the chart below, the number indicates the heat range of the plug and 7 is one step hotter than 8. The GL500 FSM recommends 8 heat range as standard with 9 for high speed extended riding and 7 for cold weather (below 41f/5c). FWIW, I use 8s in mine all winter (DR8ES-L for my GL500 engine).

It is possible that your bike's PO changed to 7s for cooler weather or to attempt to deal with the plugs fouling, or even in an attempt to compensate for the effects of the pod filters. Or that he just bought the wrong number and didn't notice.

Unless someone with more knowledge of pod filters tells you different I would recommend using the stock 8s in a place as warm as Texas.

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#3 ·
The FSM says D8EA for all CX500 models with CDI.

As you can see from the chart below, the number indicates the heat range of the plug and 7 is one step hotter than 8. The GL500 FSM recommends 8 heat range as standard with 9 for high speed extended riding and 7 for cold weather (below 41f/5c). FWIW, I use 8s in mine all winter (DR8ES-L for my GL500 engine).

It is possible that your bike's PO changed to 7s for cooler weather or to attempt to deal with the plugs fouling, or even in an attempt to compensate for the effects of the pod filters. Or that he just bought the wrong number and didn't notice.

Unless someone with more knowledge of pod filters tells you different I would recommend using the stock 8s in a place as warm as Texas.

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Awesome. I looked into it more while waiting and noticed the heat range difference. Went ahead and snagged the D8EA plugs.
thank you for the reply and knowledge!
 
#5 ·
It starts and runs okay but the throttle response seems sort of slow. I am hoping to pull the carbs and clean them soon and really look at the pilot jets as I’ve heard they can cause some of the issues.
having said that, the plugs did seem to help some as well so that’s a plus! Thanks
 
#6 ·
Have you done the stator resistance checks? It is easy to do and should be one of the first things done when chasing running problems with a CDI bikke.
 
#16 ·
Okay. I’ll try to keep it short.

my new (to me) cx500 seems to lack some pep and seems to run better on the left cylinder than the right. I swapped the spark plugs after some tinkering with other things to see if there’s a difference. Seemed to help some BUT when I pull the plugs theyre D7EA NOT D8EA, which from what I e read is stock. Would this cause issues? I am planning on replacing them as theyre cheap and if it helps at all I’d be happy but want to ensure I use proper parts.
Any help or guidance is appreciated.
I would also look at a set of carburetor kits ,had trouble with balancing my cx 500 but after replacing and cleaning of the internal of the carb she ran sweet as ,good luck buddy,
Cheers yab
 
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