One header cooler than others??

[chuckycheese]

I recall seeing information about this but couldn't find it in a search. All 4 of my headers heat up quickly but #4 is noticably cooler...it's still pretty darn hot after a minute or two....but nowhere near as hot as the other three. It's firing, for sure, but I don't think it's running as well as it has in the past.

Any ideas what might be going on? Thanks!!

[Busafied]

Could be running rich in that Cyl /or more then likely could be (probably) a sign of that plug fouling.
\
Pull all the plugs, and check the color and gap- {starting point}
Could be coil going bad, bad wire (not letting 100 % of the spark to the plug) or the plug cap could be cracked, letting the spark arc out onto the head...

Many things, work them out slowly, methodically -

GL,
Ron

[Road_Clam]

I recall seeing information about this but couldn't find it in a search. All 4 of my headers heat up quickly but #4 is noticably cooler...it's still pretty darn hot after a minute or two....but nowhere near as hot as the other three. It's firing, for sure, but I don't think it's running as well as it has in the past.

Any ideas what might be going on? Thanks!!

If your engine is simply idling, and you have 1 header that's cooler, that means you have plugged jets from debris in that corresponding carb. Do a compression check first, if compression is equall in all 4 cylinders, it's a dirty carb.

[chuckycheese]

Bummer

Thanks for the advice. I should have also mentioned that the bike runs quite well although warms up slower than it should. Once it's warmed up, it idles very smoothly at around 950 or 1000 rpm. Also, the plugs are almost new, gapped properly and look slightly lean.

If that offers any other clues, I'd sure appreciate further advice!:-D

[Dave8338]

I'd go with Road Clam on this one...it sounds all to familiar to one of the many simptoms that 650L I've given a second chance, had. Carbs, Carbs, Carbs...

[flyingace]

Seems we've had discussions on the topic of header pipe temperature before. I questioned if it's a reliable testing method and still do. I've never seen factory specs for header pipe temps, so what can you compare it to? Header pipes may have varying amounts of original thickness or some may have worn thinner over time than others.

If your bike is running well and the plugs are uniform, I myself wouldn't worry about it. I'm usually in the minority here about such things, but my bike seems to run better the more I leave it alone.

[Dave8338]

worth noting....these bikes run a pipe within a pipe system if I'm not mistaking. If the bends are not centered perfect inside the chrome exterior pipe, and it is running closer to the back side of the chorme exterior pipe, that may explain a slight difference in pipe temp to the touch, though it should feel hotter at the rear of the header, engine side, if that were the case. Food for thought.

[Road_Clam]

Seems we've had discussions on the topic of header pipe temperature before. I questioned if it's a reliable testing method and still do. I've never seen factory specs for header pipe temps, so what can you compare it to? Header pipes may have varying amounts of original thickness or some may have worn thinner over time than others.

If your bike is running well and the plugs are uniform, I myself wouldn't worry about it. I'm usually in the minority here about such things, but my bike seems to run better the more I leave it alone.

Just for giggles I measured my header temps after about 5 min of idling with an infared temp gun, and my temps were right around 155F, more importantly all 4 were within 5 degrees of each other. Temps will vary greatly from bike to bike, but like a compression test, its important the temps be close to each other. Measuring exhaust temps is a super quick method for isolating a suspect cylinder.

[Road_Clam]

Thanks for the advice. I should have also mentioned that the bike runs quite well although warms up slower than it should. Once it's warmed up, it idles very smoothly at around 950 or 1000 rpm. Also, the plugs are almost new, gapped properly and look slightly lean.

If that offers any other clues, I'd sure appreciate further advice!:-D

This is telling me you have a plugged choke passage (or an improperly adjusted choke).

[flyingace]

This is telling me you have a plugged choke passage (or an improperly adjusted choke).

Yes, I think the slow warm-up is a better symptom to rely on than header-pipe temps. The cooler pipe may be related.

[t3rmin]

Before you dismount the carbs, use a timing light or spark against the head and make darn sure you are really truly getting spark on all cylinders at various RPMs.

[Addy Leung]

I have similar problem to my GS1100 before that the #1 and #4 pipe were not as hot as the #2 and #3, and the spark plug of 1 and 4 were coated a lot of carbon. But it was still idle and no problem at all rpm. My exhaust is a tailor made by stainless steel. So it can tell the real temperature of it.
I had tried replace the coils with dyna, wiring & plugs, and checking and tuning the crabs, the problem still not removed.
Until one day I replaced the the Dyna S, all the 4 pipes are very hot now. Bike performance is totally improved. Exhaust sound are much pretty.

So if you are still using the stock ignition box and it is over 20 years old, it may be the time to replace it.

[Road_Clam]

Before you dismount the carbs, use a timing light or spark against the head and make darn sure you are really truly getting spark on all cylinders at various RPMs.

A timing light does NOT guarantee you are getting full ignition. Testing with a timing light simply says there is current passing through the spark plug wire.

[chuckycheese]

Thanks

Many thanks for all the thoughtful responses. (I would have responded sooner but we're changing internet providers so I'm using the computer at the library ).

It seems like no matter how much I adjust the air screws, all the plugs run quite lean. I simply can't make it run rich. Based on the care I've taken in running the bike and how well I cleaned the carbs last time, I can't help but doubt that they're dirty. Also, the bike runs really well after it warms up. The last time the carbs were a problem, the bike was not performing anything like it is now.

I'm not as concerned about the temperature of the header as I am about how lean the plugs are...They're not TOO lean, but they're very close. That stumps me!

[t3rmin]

A timing light does NOT guarantee you are getting full ignition. Testing with a timing light simply says there is current passing through the spark plug wire.

Well that's true, but it's still useful. The timing light detects magnetic induction, which means current has flowed through the wire. If the plug is fouled and not completing the circuit or the wire is bad and not completing the circuit or anything else is has interrupted the circuit, there'll be no induction and no blink of the light. It's true a low-intensity spark may or may not be picked up and other such caveats, but when I'm trying to figure out which cylinders are getting spark, it's a quick, easy, and mostly reliable method which can be done with the bike running.

Of course, depending on the situation, you'll have to follow that up with a multimeter, visual inspection, etc., to find out WHY there's no spark...