Header temps,... any diagnostic value???

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DonRed7

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For the last week or so cold starts are not having the motor sound as smooth and it will seem as though the bike either misses a cylinder once or twice (engine stumbles i guess is the best description). Also the level of bar vibration has been increasing to the point where today for the first time i realized that my right hand was numb....So after a 45 min spin this morning i checked the header temps (bike still running, up on center stand) pointing my infra-red thermometer at each of the four headers and was suprised at the differences.

Cyl #1 = 81/82 deg C

Cyl #2 = 81/82 deg C

Cyl #3 = 90/91 deg C

Cyl #4 = 65/66 deg C

This was not just a quick click of the meter,...I did each pipe 5 or 6 times and from both sides or the bike,....(And,.... Yes i know IR Temp units are sensitive to surface finishes) and consistently got the above #'s.

Anyhoo,....Is this telling me that i'm having cyl's 3 and 4 running rich/lean?, and does a lean cylinder/pipe typically run hotter or cooler?

I also did this to each pipe at cold start up and my main observation was that cylinder/header #4 was warming up 10 to 15 degrees cooler than the other 3 pipes.

Any ideas?????

Cheers

-Don

 
Checking header temps is a good way to tell the general conditions of things. Heck, prop driven aircraft have thermocouples (TCs) on each exhaust port and they are used to assist in making carb adjustments with altitude changes.

The FJR has a balancer tube connecting cyls #2 & 3 so they share some flow. This is a Radman question here – are the header pipes double or single wall? And finally, when at idle the Air Injection system is actively putting air into the exhaust headers for a secondary HC burn. All these things can add up to produce erroneous readings. To make the readings more meaningful the AI relay should be disabled and the readings taken right at the cylinder head/ header junction.

My brand H V-4 had a pair of -- ahem, less than reliable spark control units so I regularly used the header temps as a diagnostic tool :glare:

 
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Header pipes are single wall, I think you only find double wall pipes are exposed visually, and chromed-the double wall construction prevents blueing.. The only way to be sure of whats going on would be vacumn readings, and factory cylinder CO settings. I would guess that #3 is carrying #4, hence 4's lower temp. 1 and 2 are nice and even. A TBS would be my suggestion, you should find the vacumn readings will mimic the temp readings. Your mention of an increase in vibes also suggest this.

 
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So...... would a Rich cylinder have a hotter or cooler header?
-Don



Cooler, secondary header combustion would be very rare in our applicatio.

Keep in mind that the FJR has a secondary AIR system.......sooo.....secondary combustion would not be rare, it is designed into the system.

I would hazard a guess that 1,2 & 3 are close enough for test repeatability. #4 is the out-lyer and might be worth a look at the plug for a guess on mis-fire or ??? With the AIR system it is hard to guess whether a pipe might be running cool or hot relative to rich/lean. It will depend on the operating conditions and whether the ECM is activating the AIR or not. The surest bet is that a misfire will usually cause it to run lower temp due to the volume of umburned mixture coming thru. AIR in a misfiring cylinder will cause the pipe to run cool (no "fire" to continue secondary combustion) but it will definitely raise the temp of the cat.

 
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So...... would a Rich cylinder have a hotter or cooler header?
-Don



Cooler, secondary header combustion would be very rare in our applicatio.

Keep in mind that the FJR has a secondary AIR system.......sooo.....secondary combustion would not be rare, it is designed into the system.

I would hazard a guess that 1,2 & 3 are close enough for test repeatability. #4 is the out-lyer and might be worth a look at the plug for a guess on mis-fire or ??? With the AIR system it is hard to guess whether a pipe might be running cool or hot relative to rich/lean. It will depend on the operating conditions and whether the ECM is activating the AIR or not. The surest bet is that a misfire will usually cause it to run lower temp due to the volume of umburned mixture coming thru. AIR in a misfiring cylinder will cause the pipe to run cool (no "fire" to continue secondary combustion) but it will definitely raise the temp of the cat.
Ahhh, you caught that too. +1 on all of J's post, would've been here sooner, but a new owner of an 07 Dk Cherry just left my office complaining of a lack of power-he'll be fun here... :p ;)

 
Post #2 alludes to the AI system and recommended that the AI relay be unplugged before making measurements.

 
Keep in mind that the FJR has a secondary AIR system.......sooo.....secondary combustion would not be rare, it is designed into the system.
Jestal, I'm pretty shure my bike does not have an air injection system i look it up/down and even went on the U.S. parts site. Mine is a 13AW

Had her in for first service,..Explained the problem to the mechanic,...when i picked it up his explanation was to ride it and see what happens. :angry2:

I just fuggin' know that i've got Rich/Lean/improper burn going on. Tonight i jumped on the bike and took off with only a 20 second warm up. Accelerated,..then closed the throttle letting the motor brake a bit and she backfired like a sum bitch.

Guess it's time to pull the plugs?

-Don

 
The AI system solenoid valve is a normally open model. Air flows when the solenoid is not powered. When the ECU powers the solenoid the air valve closes. So electrically disconnecting the solenoid will allow the air to flow continuously.

 
Keep in mind that the FJR has a secondary AIR system.......sooo.....secondary combustion would not be rare, it is designed into the system.
Jestal, I'm pretty shure my bike does not have an air injection system i look it up/down and even went on the U.S. parts site. Mine is a 13AW

Had her in for first service,..Explained the problem to the mechanic,...when i picked it up his explanation was to ride it and see what happens. :angry2:

I just fuggin' know that i've got Rich/Lean/improper burn going on. Tonight i jumped on the bike and took off with only a 20 second warm up. Accelerated,..then closed the throttle letting the motor brake a bit and she backfired like a sum bitch.

Guess it's time to pull the plugs?

-Don


I thought all FJR's had the AIR system.... Look at the Yamaha parts breakdown again. Try "air induction" for a complete list of the air injection reaction (AIR) system. Yamaha calls it the "air induction" system. Possibly the air induction solenoid is stuck open so air flows to the ports all the time. https://www.yamaha-motor.com/sport/parts/home.aspx , click "procede to parts list" and enter motorcycle, 2007 and select your model. Select "air induction system" which is second on the list of subsystems and view the AIR system.

 
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Cooler means a richer mixture.

I would consider doing a throttle body sync before concluding that you have any more serious problems beyond just that.

If you run into problems or still see a significant difference after performing a sync, let us know on the board. You may other problems, but I won't even go into what they may be until after a sync is completed.

-King

By the way all, the secondary air system is only pumping air downstream just above the cats. The secondary air system will has exactly JACK to do with header temps right out of the cylinder head.

 
Cooler means a richer mixture.
I would consider doing a throttle body sync before concluding that you have any more serious problems beyond just that.

If you run into problems or still see a significant difference after performing a sync, let us know on the board. You may other problems, but I won't even go into what they may be until after a sync is completed.

-King

By the way all, the secondary air system is only pumping air downstream just above the cats. The secondary air system will has exactly JACK to do with header temps right out of the cylinder head.

I won't disagree with the need to check/set the throttle body sync but I suspect it if of minimal importance in this case. The amount of air flow difference in most cases is pretty low contributing little to the rich/lean effect. Some...but not significant in most cases I think.

You need to look a little closer at the AIR system on the FJR. It is a "pulse air" type of system where the negative pulses in the exhaust system actually pull in the fresh air past a set of reed valves. There is no AIR pump to force the air in. The system resides in the cylinder head. Reeds are in the cam cover. Ports to introduce the AIR are directly in the exhaust ports. The passages are drilled into the cam cover/cylinder head to deliver the AIR into the ports. All AIR is injected into the exhaust ports having all the effect in the world on header temps.

True, the air does go down to help the cat efficiency for oxidizing CO and HC but the AIR is introduced in the exhaust ports, not just before the cat.

 
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Fair enough Jestal.

That's what I get for applying automotive knowledge about secondary air systems into the motorcycle world.

I stand corrected.

 
Before doing anything compex, I'd go for the easy stuff. Pull the spark plug wire off of #4 and see if there's any difference in how it runs. If there is little or no change, you're missing spark, fuel, or compression on that cylinder. An automotive timing light can quickly let you know if the coil or cable has voltage. Replacing the plug and checking compression is easy enough, too. No change could obviously also mean a clogged injector. If the plug is wet when you pull it, you've likely got fuel.

 
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Ahhhhhhh,....Wow,.. thanks Jestal

I never would have thought they'd throw air into the motor there....

-Don

 
Even some car engines use the AIR delivery into the exhaust port these days. Most of the car systems use an auxiliary pump to force the air into the heads and ports but the entry point of choice for most AIR systems these days is directly into the exhaust port as close to the exhaust valve as possible.

 
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