NGK CMR7H Plug?

[ChuenouXiao]

I bought this spark plug for my XB from NAPA and it looks like just after the threads are align, it's already got tension comparing to the stock H-CMR5 from Redcat. Why is that? People say they use the NGK for there Redcat here so I don't know why It wouldn't fit. I don't want to damage my thread..... help me people! The stock H-CMR5 goes in smoothly with no tension until it reaches the bottom.

 

[GTS 666]

Yeah I wouldn't force it. But I don't know why it wont fit.

 

[Deluge]

Weird. This is the second time I've heard this. They SHOULD be the same thread.

The number you provided MIGHT be the equivalent of an NGK CMR5H, which is the same as an NGK CMR7H, it's just hotter. They both have 10mm threads, so the CMR7H should fit without any issues.

 

[ChuenouXiao]

Weird. This is the second time I've heard this. They SHOULD be the same thread.

So yours fit? Any other plug you know for sure fit?

 

[ChuenouXiao]

I cleaned my stock plug with brake fluid and brush with steel brushes. Its pretty clean now but my car wouldn't start also. I still think it may be the stock plug too even though its cleaned already. I will try to un-flood my engine to see if it will start. Do you guys have a known spark plug that will work? Note that my XB has always start up perfectly fine with this needle setting so it's either the plug or the engine is flooded. Please help!

 

[ChuenouXiao]

Weird. This is the second time I've heard this. They SHOULD be the same thread.The number you provided MIGHT be the equivalent of an NGK CMR5H, which is the same as an NGK CMR7H, it's just hotter. They both have 10mm threads, so the CMR7H should fit without any issues.

Hotter? Is that bad or good? Do you know any known good plugs that won't damage my engine?

 

[ChuenouXiao]

It seems that the NGK has a fatter entrance thread at the beginning of the thread. This cause the tension before the plug even gets to the bottom. Could it be a manufacturing defect for the NGK?

 

[Deluge]

If it's flooded, take the plug out and let it sit for an hour or so. As far as a known spark plug, everybody pretty much uses the CMR7H, so it's not the plug. Maybe the threads within the head are muffed.

 

[Deluge]

Hotter? Is that bad or good? Do you know any known good plugs that won't damage my engine?

Hotter plugs just dissipate heat slower. Colder plugs dissipate heat faster. The CMR7H is pretty much the standard with these engines.

 

[cordy]

I use these in my xb.ngk#3066=cmr7h= cold plug use in summertime. ngk#20866=cr8hsa=hot plug use in wintertime. Autolite #4194 same as cmr7h.

 

[Deluge]

Here's an NGK vid about spark plug heat ratings. There's really no need to change the plug during winter, or summer.

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[ChuenouXiao]

I also bought a NGK CR7HSA and it seems to fit the thread perfectly. My engine still wouldn't start. Un-floading and waiting over night to see if I can start it the next day. It may not be spark plug? We will see.... still troubleshooting...... Any tips people please let me know.

 

[ChuenouXiao]

Here's an NGK vid about spark plug heat ratings. There's really no need to change the plug during winter, or summer.

Hey Deluge!

Do I take off the washer from the aftermarket NGK or should i use it and leave the washer on? It seems the NGK washer is thicker and I'm not sure if that good or bad? I don't know if its even possible to take it off.

 

[Deluge]

That washer acts as a seal. Leave it on.

 

[Deluge]

I also bought a NGK CR7HSA and it seems to fit the thread perfectly. My engine still wouldn't start. Un-floading and waiting over night to see if I can start it the next day. It may not be spark plug? We will see.... still troubleshooting...... Any tips people please let me know.

Strange. That plug has the same thread size as a CMR7H.

 

[ChuenouXiao]

Strange. That plug has the same thread size as a CMR7H.

I think it's a case by case incident? Could be manufacturing defect on certain CMR7H? I don't know to tell you the truth. Going to test the CMR7H on my brother in laws XB once we run together and will let you know.

 

[ImminentFailure]

Mine had some resistance as well, same plug after replacing stock. I just ensured it wasn't a cross thread situation, and then use my spark plug wrench. Ran it in, ran it out, checked threads, ran her back in and worked great all summer.

 

[bigboysrctoys]

so is their any advantage of using the cmr7h over the factory plug? I am going to go and get a few tomorrow and start over on the tuning and just want to be sure.

 

[Guantanamo Joe]

They do seem to run the engine a little smoother in my experience... seems as if there is a tiny bit of performance gained.

 

[Guest]

so is their any advantage of using the cmr7h over the factory plug? I am going to go and get a few tomorrow and start over on the tuning and just want to be sure.

The factory plugs are cheap. All of mine have filed with in the first year. Just keep a back up.