Read My Plugs

Big_Jim59

Big_Jim59

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My pipes are pretty blue and of course that could be leftover blueing from my previous worn Amal debacle. I have put some miles on the bike with the single Mikuni set up. It seems to run fine, pull great with no flat spots or other issue. Since I am a cranked up worrier I was wondering if you all could take a look at my plugs and give me your honest opinion. The images below are the same plugs just different sides. I am running Autolite 63s which are the same type plug Debby was running.
 

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Those autolite 63 translate to an NGK BPR6ES, which is a slightly hotter than standard plug for a commando. An autolite 62 translates to an NGK BPR7ES which is a standard commando plug. You could try the #62 and see if it darkens up slightly with the cooler plug, or try an NGK BPR7ES and see if it looks different. Your plugs look about as lean as I would want to be on my commando, but it does have a nice light tan that someone running a race bike might think is perfect. I would think it's a little lean for a road bike, but if it has power in all ranges of throttle, it might just be lean and perfect....
 
Unfortunately the cross-over numbers aren't exactly the same...brand X plug will not be exactly the same heat range as brand Y. Stick with one brand..NGK is the most common..and then you can accurately choose a hotter or colder plug.
 
I think I have a set of NGK BPR7ES's. I'll try those. When I was running the Amals the plugs were dry chalky dark grey.
 
Oh, and thanks for the plug read!

I looked out in the shop and I have a box of 64 Autolite (too hot) a box of N4C Champion (not a fan of Champion anything) and two NGK BP6ES (which I thing are hotter than BP7ES) plugs. That's it. You would think I would have something in my plug box?
 
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Big_Jim59 said:
My pipes are pretty blue and of course that could be leftover blueing from my previous worn Amal debacle. I have put some miles on the bike with the single Mikuni set up. It seems to run fine, pull great with no flat spots or other issue. Since I am a cranked up worrier I was wondering if you all could take a look at my plugs and give me your honest opinion. The images below are the same plugs just different sides. I am running Autolite 63s which are the same type plug Debby was running.
Click to expand...
I'm impressed you got plugs looking that nice using pump gas on the road. Nice tan colour which yes I would be happy with when racing. Perhaps it would be best to try the BP7ES plugs for the road. I'd be inclined to be a bit more conservative road riding over a range of temperatures and usage.
 
Big_Jim59 said:
My pipes are pretty blue and of course that could be leftover blueing from my previous worn Amal debacle. I have put some miles on the bike with the single Mikuni set up. It seems to run fine, pull great with no flat spots or other issue. Since I am a cranked up worrier I was wondering if you all could take a look at my plugs and give me your honest opinion. The images below are the same plugs just different sides. I am running Autolite 63s which are the same type plug Debby was running.
Click to expand...
Well worry no more. Since you did not mention what fuel, it's assumed unleaded pump gas.
"Reading" plugs since the mandated unleaded fuel (yup, well over 40 years) is impossible unless you are:

A) burning engine oil
B) crazy rich mixture like a sunken float, etc.


Also, unless the bike is parade ridden, blue pipes are expected. After blue they go dark gray.
 
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johnm said:
I'm impressed you got plugs looking that nice using pump gas on the road. Nice tan colour which yes I would be happy with when racing. Perhaps it would be best to try the BP7ES plugs for the road. I'd be inclined to be a bit more conservative road riding over a range of temperatures and usage.
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The plugs are half tan and half white. I tried to show that in the pictures. If the plugs were all tan I wouldn't be concerned. The weather here has been mild with temperatures being in the 70s. It's not summer here in Texas yet and I do not want to run hot if I can help it.
 
Plug readings are usually only used when setting main jets after a blast up a very long road on full throttle. If you look inside the plug, there should be a black ring on the porcelain right down inside where it meets the metal. The heat range of the plug affects the rate at which the carbon burns-off. If you use hot plugs for tuning, then colder ones for normal running, you should stay safe. Most valves and pistons get burned when the bike is ridden for long periods at full throttle. Or if the exhaust system is changed without re-tuning the carbs. When a bike is normally ridden, plug readings do not mean much. If your motor misses while you are riding the bike, that can be an indication of lean carburation - always stop and raise the needles one notch. If it still misses, you probably have an exhaust leak. When I set the needle heights, I usually lower them until I get the miss then raise them one. (- Don't do that with a two-stroke.)
 
Big_Jim59 said:
My pipes are pretty blue and of course that could be leftover blueing from my previous worn Amal debacle. I have put some miles on the bike with the single Mikuni set up. It seems to run fine, pull great with no flat spots or other issue. Since I am a cranked up worrier I was wondering if you all could take a look at my plugs and give me your honest opinion. The images below are the same plugs just different sides. I am running Autolite 63s which are the same type plug Debby was running.
Click to expand...
Jim, Very curious to what jetting combination you are running in your Mikuni? Those plugs look good to me. Cheers
 
Same here, hard to tell with the gas nowadays. But I agree with Steve, they have that nice light tan look to them.
 
I used to run BP6ES for urban commuting on my MKIII and that was about right according to a plug reading. Retarded ignition timing will cause blue pipes.

Nowadays, I have no idea how to read plugs so I just tune the way it used to work and how the bike runs on the road. I now run BP7ES on the road in both the Commando (lower compression) and the Atlas (higher compression). The only time I could tell that plug readings meant anything recently was when I was chasing down a clogged muffler on an Atlas. The plug would actually foul out and be black. New muffler fixed the problem after exhausting all other alternatives.

Could someone clarify whether it's the ethanol or the lack of lead that makes plug reading not work. It seems to me that it would be the ethanol but I don't know. I've heard lots of opinions but don't know what to believe. Back in the leaded gas days, the lead would show up on the rear bumper of my 66 Pontiac and I could always tell when a customer was burning Shell gas with "Platformate," as the plugs would be yellow. Didn't the amount of lead change the color of the plugs regardless of temperature?
 
Thomasa said:
I used to run BP6ES for urban commuting on my MKIII and that was about right according to a plug reading. Retarded ignition timing will cause blue pipes.

Nowadays, I have no idea how to read plugs so I just tune the way it used to work and how the bike runs on the road. I now run BP7ES on the road in both the Commando (lower compression) and the Atlas (higher compression). The only time I could tell that plug readings meant anything recently was when I was chasing down a clogged muffler on an Atlas. The plug would actually foul out and be black. New muffler fixed the problem after exhausting all other alternatives.

Could someone clarify whether it's the ethanol or the lack of lead that makes plug reading not work. It seems to me that it would be the ethanol but I don't know. I've heard lots of opinions but don't know what to believe. Back in the leaded gas days, the lead would show up on the rear bumper of my 66 Pontiac and I could always tell when a customer was burning Shell gas with "Platformate," as the plugs would be yellow. Didn't the amount of lead change the color of the plugs regardless of temperature?
Click to expand...
To me, tan implies E0 gas, leaded or not. IMHO, with E10 (all I use) the center insulator, half-way up should be black and the rest white. Can't see down inside his plugs so if E10, I cannot read them.
 
I really need to keep track of the mixture on my old pickup with cmaper that has 2 carbs with adjustable main jets. It uses a LOT of gas so I'm reluctant to buy Ethanol-free for an extra buck and a half a gallon. I richened them up last trip to Arizona, below sea level nearby at Salton Sea. That cost me an extra 10% in fuel consumption. I read those plugs the other day when I did a compression test and they had a hint of color.

I acquired an Ispro Pyrometer and probes and a switch from a friend and am considering welding bungs on the dual down pipes. Then I could keep track on the exhaust temperature like they do on airplanes. Has anyone done that on a Norton? What sort of exhaust temperature do they run? I've watched the Pyrometers on diesel trucks and know when to back out of the throttle but I'm unfamiliar with gasoline engines.

I burnt a piston on the pickup a couple of trips ago so this isn't just an academic pursuit.
 
Thomasa said:
I really need to keep track of the mixture on my old pickup with cmaper that has 2 carbs with adjustable main jets. It uses a LOT of gas so I'm reluctant to buy Ethanol-free for an extra buck and a half a gallon. I richened them up last trip to Arizona, below sea level nearby at Salton Sea. That cost me an extra 10% in fuel consumption. I read those plugs the other day when I did a compression test and they had a hint of color.

I acquired an Ispro Pyrometer and probes and a switch from a friend and am considering welding bungs on the dual down pipes. Then I could keep track on the exhaust temperature like they do on airplanes. Has anyone done that on a Norton? What sort of exhaust temperature do they run? I've watched the Pyrometers on diesel trucks and know when to back out of the throttle but I'm unfamiliar with gasoline engines.

I burnt a piston on the pickup a couple of trips ago so this isn't just an academic pursuit.
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There are clamp on thermocouples for exhaust pipe but I don't know where to get the meters. Also, a laser thermometer will do the just by just stopping and doing the measurements.

Of course blue can mean too hot, but it can also mean light metal (cheap) pipes. Heavier steel and triple chrome plated does better.
 
Greg, Where does on get the clamp on probes. That would save me a lot of trouble is it's the right thermocouple, eg. J-type or K-typeI have the meter head.
 
Thomasa said:
Greg, Where does on get the clamp on probes. That would save me a lot of trouble is it's the right thermocouple, eg. J-type or K-typeI have the meter head.
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Definitely no expert on this! the first like shounds right but expensive.

Watlow 72XJBGF012E

Buy Watlow 72XJBGF012E - Pipe Clamp Thermocouple online on IndustrialZone. We offer fast lead times and world wide shipping on Watlow Controllers and other quality products.
www.industrialzone.com www.industrialzone.com

This link probably would work with hose clamps - very inexpensive to test.

Lots to study here:

 
I banged in a couple of NGK BPR7ESs (it was the closest heat range I could source locally) and took it for a ride. They are starting to get a tan coloring so I think I am OK. I'll just try and ignore the blued pipes.
 
Thomasa said:
I really need to keep track of the mixture on my old pickup with cmaper that has 2 carbs with adjustable main jets. It uses a LOT of gas so I'm reluctant to buy Ethanol-free for an extra buck and a half a gallon. I richened them up last trip to Arizona, below sea level nearby at Salton Sea. That cost me an extra 10% in fuel consumption. I read those plugs the other day when I did a compression test and they had a hint of color.

I acquired an Ispro Pyrometer and probes and a switch from a friend and am considering welding bungs on the dual down pipes. Then I could keep track on the exhaust temperature like they do on airplanes. Has anyone done that on a Norton? What sort of exhaust temperature do they run? I've watched the Pyrometers on diesel trucks and know when to back out of the throttle but I'm unfamiliar with gasoline engines.

I burnt a piston on the pickup a couple of trips ago so this isn't just an academic pursuit.
Click to expand...
Advancing the cam in a Commando engine gives more torque. It also makes the exhaust pipes hotter. When the exhaust valves open earlier, they make the exhaust system work harder. - that affects what happens in the combustion chamber at TDC when both valves are open. If you fit a megaphone to the exhaust pipe of a well tuned motor without re-jetting, you are likely to burn a piston. But a pipe with a megaphone usually runs cooler than a 2 into 1 exhaust system.
 
Most of my bikes had aftermarket pipes and they all had a gold to blue color past the first bend and about half way down the vertical portion of the pipe. The ones with stock pipes had some color but more subdued. Thinner metal, thinner plating on the new ones, who knows. FWIW I always ran NGK BPR8es in my Commandos.
Greg, you are right about the color band on the center electrode. You can use a dremel wheel to cut the plug apart to examine it if you are so inclined.
 
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