Air Injection Troubleshooting

With all the posts I've read here and otherwise about blanking off the air injection system, I have to wonder just what are the symptoms of a malfunctioning air injection? What benefit is derived from a properly functioning system (outside EPA) and what benefit is there from blanking it off (besides cheaper than repairing)?

Comments, flames, trolls, theory crafting, etc. all welcome (well, maybe not trolls).

EPA is about the only thing. There can be some side effects with it working properly. If your carburetors are set perfectly or on the lean side, it can cool your exhaust pipe by injecting fresh air. If your carbs are set rich it can actually heat up the pipe by allowing more of the unburned hydrocarbons to finish burning inside the exhaust.

That's interesting. Sounds like a possible "side effect" could be misinterpreting pipe blueing as an overly lean condition instead of an overly rich condition that it may very well be instead.

So, If I'm reading correctly, the system has zero effect on performance/mileage whether it's working correctly or not? Would I be wrong in assuming that?

I believe that you are right in that assumption, this system has absolutely NO AFFECT on engine efficiency.

If it's just an air injection system that injects air in the exhaust port, then it wont affect performance.

I was always under the impression that it was a recirc thing, but I guess not.

sparkn wrote:

...what benefit is there from blanking it off (besides cheaper than repairing)?....

Eliminate potential air leaks in all the hoses and connections.

Esthetically (imo), less clutter.

Good Fortune!

T_Dub wrote:

If it's just an air injection system that injects air in the exhaust port, then it wont affect performance.

I was always under the impression that it was a recirc thing, but I guess not.

You Know, that is an interesting point, I wonder what would happen if that hose was hooked up to your crank case breather. It might actually have a real benefit. But than I can also see the ports in the head getting clogged up quite quickly and than just winding up with an unintended "Natural" block-off plate. I do believe though that the system is nothing more than a mechanical pain in the A$$, and as far as we are concerned, useless.

If it's just an air rebreather as you say (my bike doesn't have one, 1977 model), then the only benefit was that it would help burn up excess hydrocarbons in the port, reducing particulate and CO emissions.

The reason why I thought it might be a recirc is because most modern car engines made with efficiency in mind are starting to include major exhaust gas recirc systems. It not only improves your emissions but it allows you to run higher cylinder pressures, giving you more power. Cooled EGR is really catching on in most of these downsized efficiency minded engines. After all, what we're all after is an increase in efficiency. F1 engines may get 4mpg, but they are extremely efficient while burning that gas, which is why tehy can produce 800+hp from a 2.4L.

Definitely not an exhaust gas recirculation (EGR) system. More closely resembles old (still used?) AIR systems that actually pumped fresh air into the exhaust manifolds.

I can see a bad situation where the glass pack can be blown out from this or at least burnt to a crisp.

From what I gather reading more and more, air injection from the KZ's era can actually do more harm than good with negligible effects on actual emissions. Burned valves and overheated exhaust systems seem to be the two biggest problems (the EXACT situation that happens when you ride and leave your choke on). This should only be possible at idle.

It would seem that capping this off and installing a good electronic ignition system is far better for emissions and engine longevity than attempting to leave this novel idea hooked up. The added risk of overheating valves and exhaust while idling (sounds like a lane-splitting argument), while small, seems like a good enough argument to me.

I think I may inspect it for health and leave it alone if it's OK, but the first sign of trouble and I won't hesitate to remove it. Since there isn't a catalytic converter to contend with, I see no problem in this.

Sounds like you've got it covered.

T_Dub wrote:

If it's just an air rebreather as you say (my bike doesn't have one, 1977 model), then the only benefit was that it would help burn up excess hydrocarbons in the port, reducing particulate and CO emissions.

The reason why I thought it might be a recirc is because most modern car engines made with efficiency in mind are starting to include major exhaust gas recirc systems. It not only improves your emissions but it allows you to run higher cylinder pressures, giving you more power. Cooled EGR is really catching on in most of these downsized efficiency minded engines. After all, what we're all after is an increase in efficiency. F1 engines may get 4mpg, but they are extremely efficient while burning that gas, which is why tehy can produce 800+hp from a 2.4L.

Did a search and found this good thread on the system. I've been wrenching on cars for years, very little on bikes (dirt bikes mostly...) and have an 81 KZ 750... My thought is that back in the 70's 80's the auto engineers were just figuring out the whole emissions thing (I assume the similar thing on bikes...) and of all the years I like least are the late 70's into the 80's until at least we had OBD I... So I'm looking at the diagram and description of this system and am considering pulling it off (I have K&N's - but might actually have the stock air box in the arsenal of spare parts given to me with the bike...).

SO, my question is - if you were to pull this system off - can you just cross over a pipe from one side to the other? I'm sort of thinking not, as you would get exaust pulses crossing over?

Then, on the breather, what do you do with that hose? The way mine is - it just sits there below the K&N's. I don't really like that. Do I put a breather on it? Cap (I don't think so...)

Now that you mention it above (otakar and sparkn - good posts) - could I rig up a PVC system... Hmm...

Basically, I just want it clean, simple, and not increasing pressure in the oil vapor chamber - causing more problems.