One exhaust pipe hotter than the others

I am a novice with motorcycles, and recently bought a 1984 KZ550 LTD. I have noticied that one of the four exhaust tubes near the engine is definitely running much hotter than the other three, like almost blue hot.
I just changed the plugs on the bike, but it could have been doing that prior, since I have not had the bike long.
Does anyone have any suggestions? Is that carb running too rich?
:S

That carb is prolly lean or has a air leak send you carbs over the WG he'll fill them with monkey snot and you'll never have to worry about it again

I should probably mention that the bike sat for a couple of days, but when I pulled out the old plugs, that was the only cylinder where the plug was wet....

suggest visual inspection followed by compression check

hot means hot coming out the valve or a portion of mix is burning in the pipe

could be overly rich and air injection is doing it's job
could be air leak on intake or exhaust
could be leaking exhaust valve

wet plug? excessive carbon too, or wet and relatively clean?

could be something else. this is armchair mechanicing after all.

The wet plug is likely the one where combustion is not taking place or not all the time. That means either no fuel, no spark or no compression on that cylinder.

The first and easiest way to check if it is an electrical issue is to swap that plug wire to the other one coming off the same coil. The 1 and 4 plugs fire as pairs and the 2 & 3 fire as pairs. If the #1 plug is the one that is wet, swap it with the #4. Same, if the #2 plug is wet, swap it with the #3.

If the wet plug and non-firing situation MOVES, the problem is electrical. Since it is on one plug only, it is most likely a bad plug wire, plug cap or the plug itself.

If the problem stays on the same cylinder with it not firing, then the next step is to buy a compression gauge at an autoparts store. Remove your plugs and hold the throttle open while you press the gauge into the plug hole or screw it in; depending on which type gauge you buy. If the non-firing cylinder has significantly lower compression, put a teaspoon of oil down the plug hole and repeat the compression test. In fact you can do this for all cylinders and record the info.

If one of the cylinders has lower compression AND it comes up significantly higher with the oil test, then the rings are likely bad or the piston/bore are worn and top end work is needed. If the compression is low and it doesn't pop up higher with the oil test, then you really need to set valve clearances. You should probably adjust the valve clearances before operating the bike anyway. This is the number one reason for poor compression and operation problems such as yours when someone first acquires a bike.

Last, is the carburetors... you may need carburetor work if the prior tests all check out OK...

The plugs I removed were old and even had some surface rust. They were mostly browned up with little carbon. The cylinder in question had more carbon on it than the others, if I recall correctly. I kept the plugs, so I can check them.
As soon as I get a decent reference for the bike, I will start running the tests recommended.
Will there be a problem with driving the bike with this problem until I get a chance to diagnose and correct?

I have one other concern as well: I do not know if the problem still persists. That pipe may have been looking discolored right from the start.

What if my changing the plugs has fixed the problem, and the pipe just looks blued from previous damage? Is there a reliable way for me to tell what is currently happening now?

And even if the problem does still persist, what test will I use to confirm I have solved the problem? Measure the temp on the pipes after I run it?

Any suggestions?

Reading your plugs should give you a good indication of how hot you are running.

Like the guys said: Blueing usually means hot as in running lean or leaky exhaust valve. A wet plug usually means incomplete combustion, which should make for a cooler temperature not a hotter one.

Take the advice offered by these guys Brian, and follow the steps they suggested. I consider myself a novice still and if there is one thing I learned from working on my bike it's that you have to be systematical. You'll usually end up spending far more time (and money) looking for a quick fix than you would have if you follow the steps :whistle:

I do agree, and will do all the tests. I am just wondering if I am going to be able to tell if I am successful.

I have a infrared heat gun, I have used it many times to find a weak or missfiring cyl, I even have used it to tune the carbs, not as good as a mercury stick but got the bike running a whole lot better

BSKZ650 wrote:

I have a infrared heat gun, I have used it many times to find a weak or missfiring cyl, I even have used it to tune the carbs, not as good as a mercury stick but got the bike running a whole lot better

Can you tell me more about how you did this? Are you talking about those little laser guns that give you a temp reading? I have one, and would like to know how I can use it to tune a carb.

it is one of the infra red guns, I checked the timing first and then started to look at the temps, I would adj the needle screws until they came close.
the lean always ran much hotter, it also works with the ones that are rich,
This is just a base line setting to get close you still need to check the clip settings and float levels.I would not reley on this other than to help get close