1981 KZ750 LTD Throaty Noise From Engine - video

I re-cleaned my carbs (pilot 3 was dirty AGAIN), then set all the air fuel mix screws back (Keihin CV34), ran the bike down the street and back noticing that it didn't want to rev down after revving up, and parked it in the driveway. Just then, the engine went from a purr to the noise in the video below where it is really throaty. It sounds kinda cool, but runs like crap in the same manner with the revving and staying high. It starts right up, which it really hasn't done before, so something is going right in the carbs, but the engine sounds bad externally.

There doesn't seem to be any air flowing out of the exhaust manifold, and no air coming out the top.

The 4 ehxaust pipes all heat up at the same time and temp by touch.

Per history, I was just about to use the Gunson Colortune to get the right mix, then balance the carbs for vacuum pressure. Things are cooling down, and I have not gotten to ride the season out! THoughts?!?

Youtube video of me getting the piss shocked out of me while trying to find the noise source:


History:
kzrider.com/forum/3-carburetor/595513-kz...ilot-mix-1981#646341

kzrider.com/forum/3-carburetor/595399-ar...-tolerance-kz750-ltd

Air injection plumbing get disconnected?

There are two spigots on top of the valve cover in the front. If you have removed the rest of the air injection plumbing, then those two spigots should be connected with a hose.

In highly technical terms, that's an air sound, not a metal sound.

So yeah, I agree with Nessism

steell wrote: If you have removed the rest of the air injection plumbing, then those two spigots should be connected with a hose.

I didn't remove any tubing. Is removing the air injection plumbing a common thing? What does it do? Plz elaborate.

Would that cause it to run like shit and behave erratic?

Thx, C.

Steel: I found this thread you were part of that seems to be what you both describe as the air injection.

www.kzrider.com/forum/2-engine/543705-ai...l=component&type=raw

I think maybe one of the hoses came off from the valve cover. I didn't have time to dig in before work, but I will in a few hrs when I get home.


As a mental environ, I would prefer to keep the clean air system in place. Is this the cause of oil on the air filter in the air box?

Sure enough, the tube going up from the airbox was out of the center air switch. Since putting the Dyna-S 3ohm coils on, they wouldn't fit under the tank. I had to bend the coils down a little to fit them in, which may have deformed the tube going up. It had popped out, causing the noise.

I performed the above proceedure, but instead of capping carbs 1 & 4, I ran a vac tube between them as I saw recommended somewhere. I ran a tube between the two valve cover air intakes. The bike sparked right up, but revved high and had other problems. New thread:

kzrider.com/forum/3-carburetor/595818-hi...981-kz750-ltd#647844

Thanks for the help, I feel like i am sooo close.