Topic: header temperature

[Schnell]

I have one of those heat sensor guns. I checked the temps of the 4 headers after a good 1/2 hour ride. I can't remember the actual temps but noted that the 2 inside cylinder headers were 30* fahrenheit hotter than the 2 outside cylinder headers. Is this normal or no? It makes sense that they would be hotter from less air cooling. I've synced the carbs, adjusted valve tappets, and the bike runs great. Is the difference okay or something to remedy?

[Schnell]

Does no one else measure their header temps?

[beemerbum]

I guess not. I'm going to try it for the fun of it. Interesting idea

[grcamna2]

subscribed

[dave500]

i wouldnt worry about it.

[Deltarider]

i wouldnt worry about it.

Neither would I. Realise that applying an infrared heat gun only indicate the temperature of the outer surface and one mechanic I discussed it with, told me it was not a reliable method.

[RAFster122s]

With double walled stock header pipes you are not reading true temps…fwiw

[TwoTired]

Does no one else measure their header temps?

Sure, with flash touching the fingers, to see if they are even across the cylinders.

Many don’t know how those cheap heat sensor guns operate.  I have one.
 The laser spot is just an aiming aid.  The actual measurement spot is below the laser spot and an inch or more wide depending on how far away the instrument is from the heat source.
Reflective surfaces can alter the heat radiation pattern among the pipes being measured.
Header pipes can be double wall and not uniform distance between inner to the outer metal layer, changing the heat transfer along its length varying from pipe to pipe.

But, if you properly use and apply the heat sensor gun under the properly controlled test conditions, it can be a fun distraction.

[beemerbum]

With double walled stock header pipes you are not reading true temps…fwiw

You are not looking for the true temperature. You are looking for the relative difference(s) between cylinders

[MauiK3]

I have a Fluke which is fairly good, I find that shiny surfaces are difficult to get consistent readings off of.

[grcamna2]

I prefer to 'read' the color of each spark plug which tells me the condition of the jetting and how each cylinder is firing and this will also give a good indication of the color/heat those cylinders are burning:you want an even color between them.

[70CB750]

I have one of those heat sensor guns. I checked the temps of the 4 headers after a good 1/2 hour ride. I can't remember the actual temps but noted that the 2 inside cylinder headers were 30* fahrenheit hotter than the 2 outside cylinder headers. Is this normal or no? It makes sense that they would be hotter from less air cooling. I've synced the carbs, adjusted valve tappets, and the bike runs great. Is the difference okay or something to remedy?

Mark Paris in his book mentions that the two inner cylinders run hotter.  It is because of air cooling and the position in the middle of the block.  Eventually it leads to difference in shape between 1,4 and 2,3 cylinders.  I dare to say it has an influence on the header temperature, too.

[BenelliSEI]

Just reading this and +1 to the above. The inner cylinders have far les cooling fin surface area to aid the cooling. For sure they run hotter!

[Schnell]

When I was active on this forum 10 years ago with another cb750, I asked if it would be smart to install cooler plugs on cylinders 2 and 3 because they receive less air cooling. Mr. Paris responded that the Honda designers had considered this and adjusted the cam for cylinders 2 and 3 with this in mind. (I think it was Hondaman, but my memory ...)

[Scootch]

I have recently acquired an infrared thermometer for this purpose to see if it would be useful in sorting carb etc issues. The jury is still out for me. Yes you can get temp readings but they seem highly dependent on a bunch of factors. I think the readings are somewhat subject to the surface. It is for sure a good indicator if you have a big problem with one cylinder. I don't think you can do fine tuning with it. More experimenting necessary...

[Kelly E]

With a Delkevik exhaust the single wall SS pipe will turn purpleish instead of gold if it's too lean. Adjust the suspect carb, a quick polish of the pipe and try it again. Just saying

[Schnell]

With a Delkevik exhaust the single wall SS pipe will turn purpleish instead of gold if it's too lean. Adjust the suspect carb, a quick polish of the pipe and try it again. Just saying

Agree about not using this for fine tuning.

[Kelly E]

With a Delkevik exhaust the single wall SS pipe will turn purpleish instead of gold if it's too lean. Adjust the suspect carb, a quick polish of the pipe and try it again. Just saying

Agree about not using this for fine tuning.

Nobody said anything about fine tuning, just an indicator of a lean condition.

[Tracksnblades1]

When I was active on this forum 10 years ago with another cb750, I asked if it would be smart to install cooler plugs on cylinders 2 and 3 because they receive less air cooling. Mr. Paris responded that the Honda designers had considered this and adjusted the cam for cylinders 2 and 3 with this in mind. (I think it was Hondaman, but my memory ...)

Interesting….🤔

Wonder what Honda adjusted..?

And whether it shows up when checking those cylinders against the the other with a degree wheel….?

[Schnell]

When I was active on this forum 10 years ago with another cb750, I asked if it would be smart to install cooler plugs on cylinders 2 and 3 because they receive less air cooling. Mr. Paris responded that the Honda designers had considered this and adjusted the cam for cylinders 2 and 3 with this in mind. (I think it was Hondaman, but my memory ...)

Interesting….🤔

Wonder what Honda adjusted..?

If I remember correctly, it was the profile of the cams for the inner cylinders.


And whether it shows up when checking those cylinders against the the other with a degree wheel….?

[Deltarider]

Nobody said anything about fine tuning, just an indicator of a lean condition.

Kelly, may I invite you to make a video - a few seconds will do - in which is demonstrated that a leaner condition results in a higher header temperature measured by your infrared gun? Depending on the bike model you own, you can turn the airscrew to arrive at a rich and a lean condition respectively. Thanks in advance.

[Mark K]

Does no one else measure their header temps?

I checked mine a month ago or more and found my exhaust pipe temps;
#1 - 182*F
#2 - 179*F
#3 - 177*F
#4 - 108*F
Checked each one numerous times, #4 stayed pretty steady at 108*F.

Found the pilot or slow speed jet was completely clogged. So for me, reading the header temps helped me find yet another issue that had to be fixed.

[Kelly E]

Nobody said anything about fine tuning, just an indicator of a lean condition.

Kelly, may I invite you to make a video - a few seconds will do - in which is demonstrated that a leaner condition results in a higher header temperature measured by your infrared gun? Depending on the bike model you own, you can turn the airscrew to arrive at a rich and a lean condition respectively. Thanks in advance.

Why do you always want to argue about stuff? I just like the resurrect old dead bikes and ride them. Not argue about it. You take the fun out of it.

[Scootch]

I measured my exhaust pipe temps. That's how I realized that I had a problem with #3 cylinder. Turns out there was a problem with the connection between the plug wire and the plug cap on that cylinder.

[Don R]

 My pipes must be too shiny for my temperature gun, I have trouble seeing the same temp on the same pipe let alone different ones.