Binding, popping or whatever you call it.

[madprofessor]

Mystery solved, you're missing parts. Parts that made the motor mounting on the swingarm strong enough not to flex.
Mounting the jackshaft plate on the rearmost 4 holes on the swingarm allows for tensioning movement (slots), and positions it for mounting 1 or 2 sprockets on its shaft...................
A single sprocket for a chain to go around along with the motor sprocket and axle sprocket, 3 sprockets on a single chain, which would be highly unlikely in my opinion. Most common would be 2 sprockets, 1 of which is chained to the motor sprocket, and the other of which is chained to the axle sprocket. Both motor and jackshaft could be adjusted (slots) to tension both chains.
The DOUBLE THICKNESS of the motor mounting steel surface (swingarm plate and jackshaft plate) strengthens it so IT WON'T FLEX.
Note: CVT backplate mounting is correct, tight to the crankcase, no part of it bolted to the frame. Keep it as is and forget about the jackshaft plate. Just strengthen the swingarm motor mounting plate so it's as stiff as if the jackshaft plate were bolted to it.

 

[Denny]

I would check to make sure the sprocket behind the driven is not a 35 instead of a 40 like the rest of that kart. To my eye I don’t see any flex in the mounting plate. Just the whole swing arm jumping which would happen any way with the wrong sprocket. Also check for the chain catching on anything. But the noise is positively chain skipping.

 

[Sauer_35]

I would check to make sure the sprocket behind the driven is not a 35 instead of a 40 like the rest of that kart. To my eye I don’t see any flex in the mounting plate. Just the whole swing arm jumping which would happen any way with the wrong sprocket. Also check for the chain catching on anything. But the noise is positively chain skipping.

I'm pretty sure it's a 41, but I'm not discounting at this point. I don't see any flexing either and putting the jackshaft plate won't stop the swing arm from flexing. My plan for now is replace the belt and chain and confirm the TAV2 plate is torqued to spec. Ill check that sprocket out too, but by eyeball it looks right.

 

[Denny]

When you get it all apart I would like to see some good pictures of the sprockets. I’m not convinced they are in all that great of shape along with the chain. That engine plate with the folded edge should be strong enough to keep the engine rigid enough.

 

[Denny]

If it was me for my own piece of mind I’d replace both sprockets too. Call it preventative maintenance. The axle sprocket looks kind of pointy. So it’s close to replacement time. But I only have a little phone screen to view it on.

 

[Sauer_35]

Wouldn't hurt. I am worried that I might run into the typical issues of having trouble getting wheels off the axle.

 

[Denny]

Start soaking them with PB Blaster now.

 

[panchothedog]

I am with MAD Prof. on this one. I think your motor mount plate is flexing.
If it were mine I would try to stiffen the plate rather than put the old Jack shaft
assembly back on it. It might take some added metal and a trip to the welding shop but the original plate is so long I think it's flexing on you. The plate style
torque converter on there now are so simple and reliable, I would stick with it.

 

[Denny]

The easiest way to tell if it is the motor plate or not is put a jack under the center rear of the swing arm and grab the engine and try to move it. You might want to be standing on the back of the swing arm also at the same time.

 

[panchothedog]

Another idea. If you have extra trustworthy people. Stand on the back of the swingarm ( feet out on the edges ) hanging onto the roll bar for support and balance, while someone drives the kart. Should give you a birdseye view of what the heck is going on back there.

 

[Sauer_35]

Yesterday I put a Jack under the frame and left the swing arm unsupported. I watched it as it spun up. One things noticed was the chain seemed wore out, but it’s didn’t bind up when it was off the ground. It was dark some I’m going to repeat that process today.

 

[Willie1]

Yesterday I put a Jack under the frame and left the swing arm unsupported. I watched it as it spun up. One things noticed was the chain seemed wore out, but it’s didn’t bind up when it was off the ground. It was dark some I’m going to repeat that process today.

If you look closely in picture #5 you can see that there is a larger gap between the sprocket and the side plates of the chain than there should be - as if the wrong series or width chain is being used. And has been mentioned, there is noticeable chain wear shown in pic #7. IMO the issue is being caused by a worn out #40 chain being run on #41/420 sprockets.

As to there being a flex issue? Possible. While I can't see the stamped steel motor plate flexing, given the width of the rear swing arm assembly and the dia of the tubing used - I guess it's possible the swing arm is flexing in the manner shown. You could clamp some stout angle iron across the back to see if it helps.

 

[Sauer_35]

Just to let everyone know I fixed this issue. Apparently the swing arm had broken at one time and when it was weld back it was twisted and fixed poorly causing the axle to be slight twisted. I got a replacement swing arm and it fixed the issue.

 

[Hellion]

Just to let everyone know I fixed this issue. Apparently the swing arm had broken at one time and when it was weld back it was twisted and fixed poorly causing the axle to be slight twisted. I got a replacement swing arm and it fixed the issue.

Got pics of the poor repair on the old swing arm? Be neat to see it for autopsy purposes. . .

 

[Sauer_35]

Got pics of the poor repair on the old swing arm? Be neat to see it for autopsy purposes. . .

Unfortunately I handed it off the trash man before I took pictures. It had about a 20 downward bend toward the rear of the cart.