Engine Trouble spark plug help

Slogger · May 8, 2015

Hi man,
Just get one of each, they last about forever, really. Clean and check the gap occasionally.
I ran a 5 in the winter cold, a 6 when it got into the 50's and a 7 now. An 8 might be good in the heat of summer in the desert. I think the 7 is cold enough, myself.
It gets into the 90's around these parts, not too bad but pretty warm.

SRPM · May 8, 2015

Thanks but I just found out the store doesn't have the B6HS only the B7HS's so I'm going to het a couple of them.

SRPM · May 8, 2015

Just got back from the auto parts store with two of each NGK B7HS and B6HS what would you recommend for a ride to work in the morning weather says it's going to be about 50°f. Thanks rpms

Slogger · May 8, 2015

How hot will it be coming home?

It isn't all that critical. The higher numbered plugs transfer more heat out of the combustion chamber so they are 'colder' running plugs. On the old NGK site I think it was 50 degrees C difference for each step. The 7 runs 50 degrees C cooler than the 6. Colder plugs are for high rpm running in hot weather. Too cold of a plug will start fouling at low speeds and having long warm-up times.
A hotter plug is fine in cold weather for putting around, never working the engine hard. Hard running with too hot of a plug can burn a hole in the piston.
The 6 or 7 should be fine.

SRPM · May 8, 2015

It says about 60°f from the ride home. Its up hill basically both ways the first hill I have to pedal with the engine to get up the other one is less steep but I still have to pedal a bit to help it along.

kerryh · May 9, 2015

Hi guys, I'm reading this with great interest. I live in phoenix where it is common to be 115-120F daytime and not less than 90 even at night. I'm using a 6 at about a 24:1 ratio to try to compensate. should i also be running an 8? (didn't even know they were sold...)

SRPM · May 9, 2015

If you read Sloggers post before my last he says

Slogger said:
How hot will it be coming home?

It isn't all that critical. The higher numbered plugs transfer more heat out of the combustion chamber so they are 'colder' running plugs. On the old NGK site I think it was 50 degrees C difference for each step. The 7 runs 50 degrees C cooler than the 6. Colder plugs are for high rpm running in hot weather. Too cold of a plug will start fouling at low speeds and having long warm-up times.
A hotter plug is fine in cold weather for putting around, never working the engine hard. Hard running with too hot of a plug can burn a hole in the piston.
The 6 or 7 should be fine.

so a 7 would keep your engine 50°c cooler and the 8 should be 100°c cooler if my understanding is correct. My problem it seems was I was running to cold of a plug on to cool of a day. I would try it out couldn't hurt, but I would also get a second opinion.

Slogger · May 9, 2015

kerryh said:
Hi guys, I'm reading this with great interest. I live in phoenix where it is common to be 115-120F daytime and not less than 90 even at night. I'm using a 6 at about a 24:1 ratio to try to compensate. should i also be running an 8? (didn't even know they were sold...)

I would.

Slogger · May 9, 2015

SRPM said:
If you read Sloggers post before my last he says so a 7 would keep your engine 50°c cooler and the 8 should be 100°c cooler if my understanding is correct. My problem it seems was I was running to cold of a plug on to cool of a day. I would try it out couldn't hurt, but I would also get a second opinion.

Not the engine, just the combustion chamber temps, all other factors being equal. If you have too lean a fuel air mixture it will over heat anyway, for instance.

SRPM · May 9, 2015

Oh but doesn't combustion chamber temp effect engine temp. If combustion chamber is running cooler then less heat is applied to engine right?

Engine Trouble spark plug help

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