Tweet!

1984 gpz750: This year I've really been riding my gpz, after a two years of it just sitting there looking sad at me. But lately I've noticed something. When I really crack the whip, and the engine is pulling hard under load, I hear a "tweeting" noise from the engine - the engine runs fine while the tweet occurs, so I'm not sure if I'm hurting my engine or not. When I back off a bit, and let the engine pull thru the rpm range at a more leisurly rate - no tweeting.

My gpz has a stainless supertrapp header + muffler unit, K+N pod filters, and a stage 3 Dynojet kit. I've had the carbs recently cleaned/sync'd, and the oil is fresh. I've had the valves shimmed a couple thousand miles ago, and I also had the cam chain tensioner replaced a few years ago.

The only thing I can think of is that the valve train is a bit out of whack (almost no shops in Metro Detroit will even look at an old KZ engine)? Or, am I just hearing the sound of the engine coming back thru the carbs + pod filters?

Any of you guys ever hear the tweet?

Not on this configuration but a friend of mine years ago had a Norton Commando that would tweet when going down through the gears.

I'd check the tightness of the intake and exhaust system for things that move or vibrate out of place. Exhaust gaskets can compress causing loss of power and strange noises.

I'd guess you have a tear in one of your pods, and when you pull a lot of air through it's whistling. If you have just let it sit without any maintenance you should know that oil-wetted filters (both foam and fabric) will disintegrate over time. Check your filters.

Hmmmmm, interesting....this spring I cleaned and re-oiled the filters. Maybe I didn't wet a spot or two in the fabric waffle....

But, the tweeting is more high pitched metallic tweet, almost like a machine gun firing bb's at a frying pan, but very faint.....disappears when I back off the throttle a touch [lighten the load on the engine].

You sure your engine is just not pinging. What gas are you using? Have you pulled plugs to look at them? Adjusted the cam chain?

Hope the sound is not "pinging" which is a dangerous condition due to detonation (aka premature combustion or pre-ignition). Often apparent from examination of spark plugs appearing "white-hot" or evidencing tiny aluminum "balls" or metal bits around the plug tip.

Can be caused by too high compression (perhaps from carbon build-up inside the combustion chamber), or wrong size spark plugs, or need for higher octane fuel, or incorrect ignition timing (perhaps too far advanced).

Pinging sound is usually heard when the engine is under load, and even at lower rpms.

Good Luck!

I use premium fuel exclusively. I'll check the plugs this weekend!

You might want to use regular as these scoots prefer it!!