TOPIC:

If you statically timed the Dyna in the full-advance position (by grabbing the rotor and twisiting it forward while checking timing), then the knock is not related to the Dyna. This should also eliminate fallen rubber pieces as the cause. If they fell off, the result would be the timing is retarded at lower RPMs (as long as you timed it with the advancer at full advance).

It can still be a weak spring causing some knock, or the throttle issue causing some knock.

loudhvx wrote: With manual slide carbs it's easy to get knocking if you give it too much throttle while going slow on the highway. This is definitely more noticeable on a Gpz.

Is this just a characteristic of this carb design? Would lowering the needle clip or increasing the main jet size help?

I have determined my problem is heat related. In the morning (no traffic) there is none to very little ping. In the afternoon (1 hr sitting in traffic on and off) I have to be very careful with the throttle or it will ping like a boss.

Lean.
Steve

swest wrote: Lean.
Steve

Ya I am not sure why that would be the case but I really don't think it is the timing as the Dyna is statically timed full advanced.

I guess I need to get some mini drill bits.

swest wrote: Lean.
Steve

it might be lean but as the day gets hotter, the air density decreases so the mixture becomes slightly more rich. I'd try retarding the timing a few degrees to see if it is pinging due to ignition timing, then decide if it is detonation or pre-ignition.

There's another thread where the advance unit is suspect. Who knows what the PO changed. I'd check on this first.
Steve

The_Proletariat wrote:

loudhvx wrote: With manual slide carbs it's easy to get knocking if you give it too much throttle while going slow on the highway. This is definitely more noticeable on a Gpz.

Is this just a characteristic of this carb design? Would lowering the needle clip or increasing the main jet size help?

I have determined my problem is heat related. In the morning (no traffic) there is none to very little ping. In the afternoon (1 hr sitting in traffic on and off) I have to be very careful with the throttle or it will ping like a boss.

It's not a mixture issue. And it's not really a design issue. It's more of a throttle control issue. It was understood, long ago, that manual slide carbs should have their throttles rolled smoothly based on the resistance you feel from engine vacuum pulling the slide against the slide bore. If you open too fast, you'll notice it's easier to pull, and the motor will stumble. When CV carbs came around, you could just twist the throttle as fast as you want, and the vacuum will determine how fast the slide actually opens. You can still get knocking with a CV carbs too, but just to a lesser extent than with the manual carbs.

The real issue is that the mechanical advancer, even when working properly, is almost an all or nothing device. The transition range is relatively narrow. So when you are cruising at just over the RPM where full advance has been reached, you are already at the cusp of being too advanced. That same amount of advance will be just right at higher RPMs. So if you are cruising at that lower RPM, I think it's like 3200 RPM, and give too much throttle, the almost-too-advanced-timing, along with the too-far-open-throttle, will start to cause knock.

Now I don't know if you are in fact opening it too fast while cruising or not, but I would assume you would notice if you roll the throttle back, the knocking stops. Then you will have to roll the throttle back on more slowly. Obviously, if you need to move quickly, you would just knock the shifter down two gears and rip the throttle as much as you want.

I just finished wideband-jetting on a KZ550A with TK22's. It started out way too rich due to faulty rebuild kit needles being too skinny. Then we went to stock jetting which was way too lean for pods and a Mac. Then eventually go it dialed in with just needle shims. I spent many hours on the highway doing all sorts of throttle transition tests, and the temps have been in the 80's and 90's. Heat is always an issue with knock, but through all of the different ranges of mixture settings, there was no noticeable difference in knock characteristics due to mixture. I wasn't looking for any, specifically, but still none caught my attention. I'm always listning for it because one of my Gpz, with bumped compression, is very prone to knock if I give it too much throttle at lower RPMs in high gear.

Also, as Bruce said, your mixture actually gets richer as the engine and carbs warm up.

EDIT: So the next step is to confirm timing with a strobe. You just need to confirm the advancer starts to advance (moves off the F line mark) at about 1500 and doesn't get to fully advanced (two line mark) before 3000.

For reference, here is the desired curve.

Looks like I will be dissembling the ignition advancer on my lunch break.

Bike won't exceed 6000 rpm in 3rd gear or higher (bogs down). Starts to break up above 4000 rpm. Won't exceed 45 or 50 mph.

I am very confused, last week I spun the advancer with my hand and it snapped right back but I am not sure what else could cause this.

Are you saying it no longer moves freely? If so, then sticking at full advance would cause knock, but not limit the RPM. If it's stuck retarded, that would cause the RPM limitation, but not the knock... unless it's alternately sticking in one position then the other.

I am currently unsure if the advancer is stuck. I will find out in about an hour.

I do know that a week or so ago it moved freely when i manually advanced it with the engine off. This is why I did not suspect the timing but I obviously have a problem somewhere.

If it is detonation then it can cuase big problems. I think I may have wrecked a piston when experimenting with too much advance on my 550. The top end was smoky and rattling and due for a rebuild so a sort of test to destruction.

It is not the timing advancer. Mine is in great shape. Snapped back properly. Just in case I cleaned it and relubed it with motor oil.

My problem still exists. I am going to switch to the second clip on the jet needle and see what happens. I can smell gasoline in the exhaust.