Low RPM knocking

I have completely rebuilt this engine. Heres the problem though.

At any RPM below around 1200 theres a knock that seems to be coming form the back of the tranny area. It goes completely away above 1300 ish and its smooth as silk from there on up.

I have synced and resynced the carbs using the Morgan Carbtune Pro tool I have. thought maybe it was ignition related so I nixxed the points and went to the Dynatek ignition. i thought that maybe it could e clutch basket bearing related but squeezing the cutch lever in and out doesnt seem to change the sound any. Best Youtube Video I could find that sounds close to this knock is here....but I dont thin k its cam chain tensioner related as the sonds coming from the back of the cases and not from the jugs or top end areas.

He need to hear your bike. I don't think that guy knows what he's doing. If it's like that, there is a clogged jet or jets. The pilots are very small. I use a guitar string or strand from a wire brush to be sure they're clear. His is way out of sync but with clogged jets he'll never get it right.
Steve

Hey Chuck I also have the same knock in my 1979 Sr 650. I brought it to my long time macanic he said that he he had 3 of these bikes and they all did it at low rpm. He says it's just the starter clutch, not to worry, drove his bikes for 20 years and never had an issue at all. I'm not 100% sure that he's right but I hope that helps set your mind at ease.

If it goes away at 1300, my suspicion is with carb balance and the typical primary chain rattle and clunk....although I can't exclude a bearing failure somewhere in the engine / transmission....

Have you dropped the oil and checked for metallic residue (silver - grey) in oil or on plug or other signs? Another trick is to cut the oil filter apart on a shallow pan, stretch out the pleats and look for tiny metal bits on the outside surface....

This isnt my first rodeo with carbs....but it is my first rodeo with a Kawasaki. Carbs were dipped 24 hrs in the Berrymans, gone through meticulously by ME..I use a plucked wire from a wood handled wire brush for poking the holes. I used a full can of carb spray to flush the passages afetr coming out of the dip..followed by the air nozzle from my air hose each way down all openings to be sure the loosened crud was flushed out. Float hyts rechecked per the OEM service manual I have. Im leaning at its either the primary chain or its a worn clutchn hub bearing or even a combo of the two.

As for a video. Aint gonna happen for a while till I get my 82 GPZ1100 off the lift.

gdk wrote: Hey Chuck I also have the same knock in my 1979 Sr 650. I brought it to my long time macanic he said that he he had 3 of these bikes and they all did it at low rpm. He says it's just the starter clutch, not to worry, drove his bikes for 20 years and never had an issue at all. I'm not 100% sure that he's right but I hope that helps set your mind at ease.

Both of the 650's I've worked on did this when I got them - the noise went away when the carbs were synched properly....primary chain!

Have had many, MANY Honda fours and CBX's do the same thing, also....

Just uploaded a pic of the bike after I did the full tear down and rebuild..minus the badges. I did all the painting also. Ive restored a lot of UJMs so I k now my way around bikes and such. Just so unsure about this sound and Im setting here second guessing it a lot. Really dont want to open up the clutch cover if I dont have to.

Thanks good too know. Have no spark in 1 and 4 right now. Thinking it's a coil. Gonna check it out tomorrow in the daylight

I don't think removing the clutch cover is going to help at all - it likely won't tell you much, and if you have to go that far, you are going to have to go further than that before you are out of the woods....

How close are you with the synch? I use mercury tubes and set to within 0.5 cm Hg between all four cylinders. I can get these old bikes running very smoothly (and quietly) by taking my time and using a big fan blowing cooling air to the front of the engine to simulate the bike going about 30 mph - this prevents overheating. You really can't synch the engine properly when it gets too hot. I also use a infra-red thermometer (a really good one held at the same distance for all measurements) on the exhaust headers right out of the head to check the engine's balance at idle.

Other than that, you could be dealing with a loose chain or a damaged bearing....

gdk wrote: Thanks good too know. Have no spark in 1 and 4 right now. Thinking it's a coil. Gonna check it out tomorrow in the daylight

A '79? Does it have points or electronic ignition? Check the 1-4 coil first (easy - swap it for 2-3 coil and see if the problem switches cylinders), but if that isn't it, then you might have some loose wiring, or - problem with 1+4 points or 1-4 electronic crank trigger hall effect switch (I have installed many Dyna S ignitions because of the latter).

77 650B1..Built 7/76. It has new coils and new Dynatek ignition so there arent any ignition related problems here. My noise is about center of the engine at the back side of the clutch cover..like right to the rear of the dome part that covers the basket area.

Only reason I was debating opening the clutch cover was to take the basket out and feel for any play in the clucth basket roller bearings or the input shaft bearing

I would check your oil and filter for metal first before pulling the cover.

It is unusual, but not impossible, that a roller or ball bearing will make a knocking sound only at slow speeds. More likely an anti-friction bearing will produce a whine or a constant humming / growling sound that increases with speed an load.

Now that you say the noise is coming from the center of the clutch cover - I would re-check the clutch adjustment AT THE PUSH ROD under the left side transmission / final drive cover as per the FSM. If you don't have some free play there, the release bearing will be damaged in fairly short order....

Or maybe it was NFG to start with?