86 Club Car Ds "hopping"

[judamonster]

I have an 86 with a flathead. I bought it last fall after minimal drive testing. Nothing felt off. Over the winter i lifted it, bought a used driven clutch, had it machined and added a torque spring. Replaced the starter belt. I lowered the engine after the lift, engine snubber is still not at rest, i may have to loosen the lift to let the engine settle. No issues when running it in service mode. Test runs in my small backyard have the cart hopping and half throttle. I cannot go any faster for now due to the size of my yard. The hopping feels like a vibration with a up/down motion. Feels like it is rpm driven-stops hopping when i let off the gas. What could this be? worked fine last fall-i assume the drive clutch wouldn't suddenly be bad.

Items worth noting:I am using the drive belt that came with it, I ordered a replacement but it was way too loose. One of the white wires with black stripe to the micro switch was disconnected. I did not have to loosen the starter to get the belt on, i was able to force it.

[Fairtax4me]

Couple things come to mind.
Who built the secondary clutch? You or someone else? The secondary is directional and if improperly assembled it will not keep proper tension on the belt.
Also the moveable sheave has to be pre-tensioned during assembly or else again, there will not be proper tension on the belt.
Distance between the engine and transmission is very important to proper clutch operation. If they are too close or too far apart you will have problems. Too close will cause the belt to skip and chatter which will cause the issue you describe. From the center of the crankshaft to the center of the input shaft needs to be 9-5/8” exactly.
Also when you installed the lift did you unbolt or remove the small dog bone brace that connects the bottom of the transmission to the cradle? That small brace needs to be there to keep the transmission from twisting forward towards the engine. If it’s not there the transmission will be able to rock forward when under load and the belt will chatter on the clutch.

[judamonster]

My driven clutch was not rebuildable. Cartpartsplus sold me a used unit that they machined and added the spring. I will measure the shafts tonight. Start there and move on.

[Springbok]

Subscribed.

[judamonster]

FYI, i put the stock driven clutch on and the problem persisted so i put the upgraded clutch back on. I loosened up my throttle cable as it was maxed out. I also loosened the rear lift to allow the cradle to settle in front. It is still suspended above the frame, just not as much. Each one of these things reduced the vibration a little, and collectively it is to the point in which it is acceptable. The range it is experienced went from 75% of the power curve to 3%-and i you have to look for and hold it there to get the vibration.