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Hi guys and gals, I recently got an '89 EX500 with 60k miles. I brought it to the dealer for a diagnostic and he said only one cylinder was firing. I saw on the internet someone posted that you can check the exhaust to see if one or both are firing. So I checked and there are puffs of air coming out of both exhausts without any noticeable difference between the two. Um, what's the deal ??? Thx
 

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Air will go out the tailpipe weather it's burned air/fuel or not. It's not a very accurate way to determine that it's firing or not.
 

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If the cylinder pulls in air/fuel on the intake stroke, & it does not burn it (no spark or really bad compression), then that unburned gas & air will go out on the exhaust stroke.

1) there will be way less volume of gasses since there was no fuel->combustion gas conversion.

2) that side of the exhaust will be cooler, as long as the exhaust (or other heat source) from the other cylinder doesn't ignite it. The crossover pipe allows some mixing of the exhause from the two cylinders but I think (am ready to learn otherwise) that the main purpose of the crossover pipe is to equalize out-of-phase pressure pulses between the exhaust sides: maybe for a little "header-like" scavenging effect as well as less intense pulsing noise (quieter exhaust).

3) raw exhaust ought stink of fuel (minor whiffs only!) and is bad pollutionwise & a burn/flame/bang risk.
 

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let the bike idle for a minute or so, feel both of the pipes near the motor the one thats not warming up is the bad cylinder
 

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what ddenn35 said, with one important modification: touch a damp rag to the exhaust headers. You will hear a sizzle and see a bit of steam if it's warmed up enough. Don't touch it with your fingers. That wouldn't be fun. Watch where your hands are when you're doing this (don't brush against the pipes), and be careful.

-jcs
 

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Discussion Starter #10
Yeah it has a crossover pipe...this morning I put a bare hand on each can after starting it and they warmed up equally
 

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my old bike ran on one cylinder, these were my symptoms:
-slow as heck, a pre-94 ex500 will be a damn missile at WOT with both cylinders functioning properly
-shoots fire, I wish my new bike did this. Nothing like blasting a fireball in the face of tailgaters
-you may notice inconsistencies between spark plugs, my bad cylinder had a black plug from oil leaking into the cylinder somehow
-one exhaust pipe significantly hotter than the other
-my bad cylinder was spotty, it would activate once the oil burned off the plug, resulting in a popping sound and corresponding doubling of horsepower.

It's usually pretty obvious which is the bad one, whichever side of the engine/exhaust is significantly colder/more F'ed up
 

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Having just gone through diagnosing one of these, the quickest way to check:

1. Make sure your bike is COLD. Like hasn't been run all day.
2. Start your bike
3. IMMEDIATELY start feeling the exhaust pipes right behind the front wheel, where they come out of the engine

You'll notice that one of them gets too hot to touch bare-handed almost right away (probably within 15 secs or so) while the other takes a bit longer (about 30 secs or so). The one that took longer to heat up is the one that isn't firing. They'll both get hot within a minute and you'll always feel puffs of air coming out of both tailpipes.
 

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this is an old post so im sure you have it fixed by now, but try pulling the plug wire and listening for a change in tone, or in my case, when i pulled the only cylinder that was firing, the bike shut down, when i pulled the cylinder that wasnt firing, nothing happenned, sounds a little better than burning your hand on the exhaust pipes and still not knowing which one is firing for sure
 

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knarlydood said:
Hi guys and gals, I recently got an '89 EX500 with 60k miles. I brought it to the dealer for a diagnostic and he said only one cylinder was firing. I saw on the internet someone posted that you can check the exhaust to see if one or both are firing. So I checked and there are puffs of air coming out of both exhausts without any noticeable difference between the two. Um, what's the deal ??? Thx

Try not to start the bike on one cylinder to much, but go ahead a run it for about 30sec to a min and a half, an feel the exhaust. if it is only running on one cylinder. the pipe will be cold, that would be the side the cylinder is on running on.
 

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You don't have to feel anything, all you do is spray some water on the pipes and you will visibly see which one is not firing because the water will just roll off, the other will evaporate instantly.
 

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you could also crack an egg or try to cook bacon on them, but the spraying water concept looks like a winner to me : less harmful, less greasy ;) ;D
 
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