Hard jerking when accerlating

[sd3838]

I bought a Manco Connador II and have put a new 420 chain, both sprockets and belt. It has a Comet 30 series torque converter. It has a hard jerk when you try to accerlate from a stop. The chain is not loose with just a slight slack. The gears appear to be in alignment, but I haven’t put a straight edge on it yet. I was thinking maybe the key on the engine shaft? Could a fault in either drive pulleys cause this? Anybody got any suggestions? I jacked it up, but it wouldn’t do it with no load?

 

[Brianator]

Is there any kind of noise that goes along with it? If you could post some pictures with close ups of the engine/tc/sprockets/chain from different angles that would be super, it should make it easier to identify the issue. I wouldn't suspect the key because you said it happens when accelerating from a stop and haven't mentioned anything else that happens (ie. something happenening when letting off the throttle) but I also wouldn't rule it out, have a look at it. Im suspicious of the driven pulley myself. To create load with the wheels off the ground, use the rear brake

 

[Karttekk]

The 30 Series torque converter takes an asymmetrical belt. One edge is flat, the other is angled or beveled. Make sure the flat side faces the engine and the angled or beveled side faces the outer sheave of the drive pulley.

 

[sd3838]

Thanks ya’ll, I couldn’t see the forest for the trees, good suggestions. I’ll post back in a day or so.

---------- Post added at 11:12 AM ---------- Previous post was at 11:10 AM ----------

I know the pulleys are positioned right, but not sure they’re aligned perfect

 

[KMART014]

Did you ever fix the issue? Im having the same problem

 

[sd3838]

Not yet, working on my backhoe today, but will be on the go kart tomorrow. I’ll let you know

 

[sd3838]

Ok, Looked at it right at dark tonight and the engine and jack shaft is torquing to the side under a load and I think it is putting the small sprocket out of alignment with the axle sprocket. Something is either bending or a weld may be broken. I’ll look at it tomorrow and see what may be causing it and post back.

 

[sd3838]

Hard Jerking when accelerating

The two braces underneath the motor were completely broken in half.

 

[Brianator]

Yup. That'll do it!

 

[Karttekk]

Whoa!

 

[landuse]

I am surprised the chain stayed on

 

[sd3838]

I noticed that the washer nuts were barely covering the engine mounting slots and needed bigger washers. I saw where somebody mentioned in another thread of possible problems with the chain seating on a 9 tooth sprocket, which is what I have. I replaced the original 9 tooth sprocket because I didn’t know better and even though the axle sprocket was a 60 tooth, I didn’t want to increase the speed.

The chain did jump off when I first got it and I replaced everything. I’m curious as to what caused the breaks. The metal braces are 1/4 x 1 and the engine is a 6.5 Robin

 

[sd3838]

Ok, so The chain I replaced with is a standard chain. I did not oil it as I assumed it was prelubed. I still had jerking after welding the motor supports back. had to widen motor slots slightly to get exact alignment of the sprockets. Got proper slack and still had the jerking. Took chain off to soak it in bar lube and the links were still in a bind. I've ordered a gold chain and I'm going up to a 10 tooth jack sprocket because of reading that it is better than the 9 tooth because of less binding or better wear? Since my axle sprocket is 60 tooth I'll have the 6:1 ratio, but my concern is too much top end. The cart is for my 14 yr old and I'm just guessing that it goes around 40 now. I haven't been able to determine the adequacy of the torque because of the jerking. I'm wondering if maybe I should go to a 7" driven if I don't have enough low end torque to compensate for the 12 tooth or get a higher tooth axle sprocket? Any thoughts or suggestions would be greatly appreciated.

not 12 tooth, but 10 tooth

 

[sd3838]

I put the new 420 gold chain from Protaper on and when I tried to take off, it still jerked, so I immediately parked it. Started searching old posts again after figuring out, I couldn't get a 72 tooth axle sprocket in a 420. I found the thickness of a #40 sprocket was thicker than a #420/41 sprocket and measured mine and found I had gotten a #40 sprocket. Apparently, the chain is riding slightly high on the sprocket. I think originally, I had different problems, like the broken motor supports and alignment causing the jerking and now it's the wrong/too thick sprocket causing it. From what I've read, I'm assuming the jack sprockets are all the same with the 40, 41 and 420 sprockets? Thanks for any help.

 

[sd3838]

Finally fixed it. Had to weld another engine support, frame brace because the brace broke in the rear of the plate. Also, figured out that to
Properly align the axle sprocket, the wheels had to be tightened first. I had bought the correct axle sprocket. I had multiple problems.

 

[miniblazinbmx]

Finally fixed it. Had to weld another engine support, frame brace because the brace broke in the rear of the plate. Also, figured out that to
Properly align the axle sprocket, the wheels had to be tightened first. I had bought the correct axle sprocket. I had multiple problems.

I have the jerking from hard starts I think Ive narrowed down to a bent driven pulley. its pretty obvious on a stand.. hard to look over the seat when driving tho.. good luck.

 

[madprofessor]

The link below will show you what you cannot do with #40 sprockets...........They're too big for #41 and #420 chains. However, you can use any of the (3) 1/2" chains with the #41 and #420 sprockets without any problems. The general answer to 1/2" chains is just avoid any #40 stuff altogether.
Chain for Go Kart, Mini Bike | GoKarts USA®
Also, if you screw the throttle limiting screw in a little, it'll reduce that extra top speed, and also reduce the amount of throttle you can give it on starting off, reducing the violence of the jerking start.