780 Clutch issue-lunging!

Shack

I have a 23hp in a Stretched Club Car. It has a 780 comet with a 1-3-16" belt. It's heavy cart and carries up to 6 people.

It has always had a positive "launch", but in the last year or so, it has gotten progressively worse. Now, you accelerate normally, it moves forward a couple of feet and it's like you drop the clutch on a lawnmower....no noises, no fanfair, just whoa!!! It lunges forward...hard.

I'm gotten pretty good about pulling my foot out of it at the right moment to smooth it out, but if someone else drives, it's dangerous. At an event this past weekend, my wife was driving staffers around and pulled away from the reception area and launched a lady off the rear seat, injuring her shoulder. Now it's serious.

I took out the back seat and had my son drive. Nothing looked out of the ordinary. Drive clutch moves in, belt starts to move up the drive clutch and suddenly whoa!!! Like you dropped the clutch. It did it over and over and I didn't see anything that made me say "ah ha!!! that's it" It may have looked like it moved in just a hair, then moved back out, but....? I couldn't see how something so violent came from that little movement.

Driven clutch belt is all the way at the top of it when this happens. No noises, no grinding, whining, slipping, nothing. Took the drive clutch off and examined it; no broken parts, nothing wrong I could see.

Could a worn belt do this??? Belt tension wrong?
Does the spring inside the 780 do anything other than push the pulley back?
Is it the Driven clutch? Should the driven clutch already be moving the belt downwards to soften the engagement?
Is there something else I'm just overlooking?

For such a simple system it's eating my lunch, and wifey is not happy. Help!.

BGW

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fstg21

You can up the driven clutch tension to slow down the shift out. twist the spring tighter. It could be wearing out.

You can also clean and lube the clutch. and check for wear or a bent arm

Shack

I got ahold of Tom (CPP) and he graciously went over all the things I had checked. After some measurements we decided the issue was belt tension, with a little added CVTech (it's not a 780!!!) hard launch personality.

Moved the engine forward in the cradle about a 1/4" and 90% of it went away. Tried to move it more to completely smooth it out, and shifting gears became an issue, so went with the 1/4" adjustment.

At some point I'll go ahead and freshen the belt, and maybe go with a Comet 780, as it seems they have a smoother engagement I've been told.

Hope this info helps someone else!!!

fstg21

You can also smooth out the engagement, by removing a little weight from each of the pucks in the CVtech. literally pull out the weight discs and drill a 3/16-1/4" hole in 1 or 2 discs in each pack. drill the same number in each pack. just a tiny bit of weght can smooth it out alot. It will raise the engagement rpm by 100 or so.

BigBlockMan

Glad the belt tension helped. We do have other weights for that clutch. Of course changing to the 780 would take care of it as well. The 780 engages smoother and shifts more consistant as well.

chevydmax6

Big block man what is your thoughts on boring a 780 out to fit a 1 1/8" shaft

LVCJ

^^^^^^^^^^^^interested as well...........

raydhd

IMHO A disaster waiting to happen.Much better to turn down the crank.I doubt there is enough "meat" in the clutch to even accomplish that.

Shack

Thank you Tom! Just a 1/4" made a huge difference!!! Any more than that seemed like it wouldn't shift at idle, any less and it still had a slight "grab" to it. My buddy has the 780 on an 18hp and the engagement is so smooth! Probably change out for a 780 prior to our summer run!

BigBlockMan

Yes, not enough room in the 780 to bore to 1 1/8" the crank would need to be turned down.