Upgrade to Comet 44 or 780

[MTScott]

These chinese torque converters simply don't do the job well for me... I have two of them that have been run on the grand daddy kart with the predator 420cc.

I've taken both apart more than once, cleaned and sprayed all moving parts with graphite, and they still like to bind and not retract after only a few hours of riding (even when not under load, it will not retract). The only solution that I was actually able to do that helped them operate longer was to use bearing grease on the inner tube that the sheeve slides on. My theory is that the brass bushings are too narrow and bind. The grease (gasp) seems to have helped more than the graphite spray. I know everyone says that grease is a no-no because it'll cake up with dirt and belt dust, but it is what has worked the best so far.

Even on a gentle hill, the sheave will not retract at all as the engine slows down. It only ever retracts if there is no load at all. I've been told that this is just how they operate though, so maybe this is just how it is.

Either way, on to the actual topic of an upgrade.... I will stage 2 (at least) build this motor soon, so, 25ish HP (maybe more), 7K rpm motor. I've decided go to an actual comet brand TC, and I figure I might as well go to a 44, along with the larger driven 8.5" pulley intended for the 44. The problem with a 44, is they are no where to be found for a 1" shaft. You can find 3/4" in shaft, and 1 1/8" shaft, but I can't find a 1" shaft 44 TC unless it is used, and they are hard to find too (if you know where I can find one, please tell me).

So, option 1: buy a 1 1/8' 44 magnum TC, and use a sleeve adapter to put in on the 420 1" shaft.

But wait.... there is also the 780. There are a couple options in between the 44 and 780, but they don't seem worth messing with. Also, for the cost of the comet 44, I don't think I'll spend much more on the 780. I also can't seem to find a 780 "comet" brand. go power sports seems to sell a "quality aftermarket" brand 780, but true comet brands are not in stock.

Therefore, option 2: "Quality" aftermarket 780 TC driver & driven (unless someone knows where I can find a comet brand)

Follow up question - what is going on with Comet? Are they out of business, or just unable to keep up?

Also open to other suggestions.

 

[BrownStainRacing]

These chinese torque converters simply don't do the job well for me... I have two of them that have been run on the grand daddy kart with the predator 420cc.

I've taken both apart more than once, cleaned and sprayed all moving parts with graphite, and they still like to bind and not retract after only a few hours of riding (even when not under load, it will not retract). The only solution that I was actually able to do that helped them operate longer was to use bearing grease on the inner tube that the sheeve slides on. My theory is that the brass bushings are too narrow and bind. The grease (gasp) seems to have helped more than the graphite spray. I know everyone says that grease is a no-no because it'll cake up with dirt and belt dust, but it is what has worked the best so far.

Even on a gentle hill, the sheave will not retract at all as the engine slows down. It only ever retracts if there is no load at all. I've been told that this is just how they operate though, so maybe this is just how it is.

Either way, on to the actual topic of an upgrade.... I will stage 2 (at least) build this motor soon, so, 25ish HP (maybe more), 7K rpm motor. I've decided go to an actual comet brand TC, and I figure I might as well go to a 44, along with the larger driven 8.5" pulley intended for the 44. The problem with a 44, is they are no where to be found for a 1" shaft. You can find 3/4" in shaft, and 1 1/8" shaft, but I can't find a 1" shaft 44 TC unless it is used, and they are hard to find too (if you know where I can find one, please tell me).

So, option 1: buy a 1 1/8' 44 magnum TC, and use a sleeve adapter to put in on the 420 1" shaft.

But wait.... there is also the 780. There are a couple options in between the 44 and 780, but they don't seem worth messing with. Also, for the cost of the comet 44, I don't think I'll spend much more on the 780. I also can't seem to find a 780 "comet" brand. go power sports seems to sell a "quality aftermarket" brand 780, but true comet brands are not in stock.

Therefore, option 2: "Quality" aftermarket 780 TC driver & driven (unless someone knows where I can find a comet brand)

Follow up question - what is going on with Comet? Are they out of business, or just unable to keep up?

Also open to other suggestions.

Which direction are you running the driven???

You probably need the yellow REVERSE driven spring.

Post pics.

Comet 40 Series Torque Converters | Comet 44 Series Clutches

Comet 40 Series Torque Converters and Comet 44 Magnum Torque Converters for 8 to 18hp, 7/8

www.gokartsupply.com

 

[MTScott]

Which direction are you running the driven???

You probably need the yellow REVERSE driven spring.

Post pics.

Comet 40 Series Torque Converters | Comet 44 Series Clutches

Comet 40 Series Torque Converters and Comet 44 Magnum Torque Converters for 8 to 18hp, 7/8

www.gokartsupply.com

I installed it in proper orientation for the red spring, part of the reason I built my own jackshaft... there are pics, and some videos here:

First build, Grand Daddy

That seems excessive to me also. But you may have to drive it to see how it responds but it does look like you could go shorter. Video great idea!

www.diygokarts.com

 

[BrownStainRacing]

I installed it in proper orientation for the red spring, part of the reason I built my own jackshaft... there are pics, and some videos here:

First build, Grand Daddy

That seems excessive to me also. But you may have to drive it to see how it responds but it does look like you could go shorter. Video great idea!

www.diygokarts.com

Yea, that looks right to me.

Did you pre-loaded the red spring??
Have you tried a different hole for the spring?

The 40 series around here are on big 2 seater buggies, they don't come around very often for maintenance, they seem to be pretty much bullet proof.

 

[MTScott]

they seem to be pretty much bullet proof.

Would you say that is true for the chinese knockoff 40 series drivers as well? The driven hasn't given me any trouble, it seems to do what it is supposed to (also a chinese ebay purchase). If the actual comet brand driver will be that much superior, I could get it a go.

This is a two seater, built a bit bigger than the plans (grand daddy) and also likely heavier. Pushed by a predator 420, and it gets beat on. Picture two 120 lb kids running a 1/2 mile track with hills, and a dozen corners, drifting at full throttle through every one of them (also sometimes a 250 lb kid)

 

[panchothedog]

I have a 40 series on a large 2seat Manco Intruder. Pretty big kart. Mildly built 301 predator. Bought the 40 series from O M B Warehouse. I imagine that it's Chinese. I know for sure it is not a Comet. Absolutely no problems.

 

[BrownStainRacing]

Would you say that is true for the chinese knockoff 40 series drivers as well? The driven hasn't given me any trouble, it seems to do what it is supposed to (also a chinese ebay purchase). If the actual comet brand driver will be that much superior, I could get it a go.

This is a two seater, built a bit bigger than the plans (grand daddy) and also likely heavier. Pushed by a predator 420, and it gets beat on. Picture two 120 lb kids running a 1/2 mile track with hills, and a dozen corners, drifting at full throttle through every one of them (also sometimes a 250 lb kid)

Yea, I'd have to say the Chinese knockoffs are jus as good.

Theres at least 3 I see on the trails around here a couple times a months They are china made, 1 is a plate system, the otheres are jackshaft similar to yours. 301-420 engines, 19"-23" tires

Old logging road trails, long steep, twisty hills.

There's got to be something wrong with your driven. The spring tension is what pushes the belt back up.

As I said, I don't work on too many 40's, mostly small block stuff.
The 30's spring gets old and weak, I had 1 break and stuck in high but that was old rusty junk that needed trashed anyway.

 

[Snaker]

Even on a gentle hill, the sheave will not retract at all as the engine slows down. It only ever retracts if there is no load at all. I've been told that this is just how they operate though, so maybe this is just how it is.

What your describing here is a normal characteristic of CVT's, if I'm reading you right.
These small engine CVT drive pulleys are rpm sensing.
As long as they spin above clutch disengagement rpm's, they will stay engaged

When you go down a hill and let off the throttle, you get ground drive, where the moving machine is spinning the engine.
As long as it can push enough to keep the drive from slowing below disengagement rpm's, the clutch will stay engaged and the machine will push the engine.

It can be thrilling at times.
I had a woods trail downhill section that was right on the thresh hold of disengaging or not.
One time I could go down and have engine braking throughout.
Another time I could go down and slow just enough to disengage and it would freewheel like it was out of control.
Freaky feeling
I learned to keep just enough throttle on to keep the CVT engaged as I started the down hill even when I didn't really want throttle.

 

[panchothedog]

MTScott. I thought you were having trouble with the driven. After reading again I see that your problem is the driver. Have you tried installing the spring and weight
package. I did on mine for a complete different reason. Stronger launch. Boy did it work. It raised the engagement RPM by a thousand. Meaning the engine and driver freewheel up to 2600 rpm. Stands to reason that the same would happen in
reverse, that the clutch would " let go " at a higher rpm. Maybe a thousand higher than it does right now. The stronger springs, and lighter weights ( which both hold
the clutch open, or disengaged longer ) are sold by OMB Warehouse, and probably several others for about $ 40. I would certainly give that a try before biting a pretty big financial bullet in buying the 780 setup.

 

[Master Hack]

I have to second the springs and weights. I did the upgrade as per Pancho's recomedation and couldn't be happier. Well, I could but that would involve lotto winnings of million$$$$

 

[BrownStainRacing]

Seems like I preach too much about STALL (engagement rpm) speed.

It's amazing the difference how ALL these single cylinder TORQUE utility engines will change with only 300-400 more rpm stall.

It'll make you think twice...... uhm, maybe.....I didn't pick the right gear ratio.

When you change the rpm engagement, the disengagement changes too.

I thought @MTScott was having a stuck belt in high.

The STOCK 40 series driver has a stall speed around 1800 rpm, if your big block is idling close to that, it will not disengage, as @Snaker said, engine braking is happening until it gets below 1800 rpm.

A tachometer is a very useful tool when tuning.

 

[MTScott]

Thanks gents. When I was referring to issues how it reacted on a hill... It was climbing a hill. I was hoping that as the engine slowed down, the sheave would retract on the driver effectively gearing it down, but it didn't. If you approach the hill with speed in "high gear", that's seems to be where the driver stays, then the engine bogs as you slow down.

I could see how the springs would help, and I already have them (red). I just haven't put them in, so I should give that a go.

Also, I was able to adjust the stock carb to idle around 1200 rpm, so that isn't an issue, but heavier springs should operate better anyway.

 

[Snaker]

Thanks gents. When I was referring to issues how it reacted on a hill... It was climbing a hill. I was hoping that as the engine slowed down, the sheave would retract on the driver effectively gearing it down, but it didn't. If you approach the hill with speed in "high gear", that's seems to be where the driver stays, then the engine bogs as you slow down.

I could see how the springs would help, and I already have them (red). I just haven't put them in, so I should give that a go.

Also, I was able to adjust the stock carb to idle around 1200 rpm, so that isn't an issue, but heavier springs should operate better anyway.

Yeah, that's a different thing. That is part of the Torque Sensing function, a part of the driven pulley.

Torque Sensing (TS) senses the load from the drive wheels.
Torque = load so I'm going to call it load sensing because its easier to envision
Think: Drive pulley is rpm sensing and driven pulley is load sensing
TS is all about the angle, the angle of the driven pulley cam

Older, pre-TS CVT's didn't have any angle, the movable sheave moved laterally only and the contra spring was solely used to keep tension on the belt.
The up/down shifting was solely reliant on the rpm sensing of the drive pulley flyweights, controlled by the throttle (and engine hp)

TS is a feature that senses additional load and forces a downshift to keep the engine at its tuned for rpm.
I call a forced downshift a backshift.
That is different than a "normal" downshift where you simply let off the gas.

The various CVT components can have some effect on this:
hp
flyweights
contra spring
contra spring pre load positions
TS angle (different angles)

Also, what ever is changed to affect downshifting will also affect upshifting and vicey=versey so it is something of a compromise
TS is involve with controlling backshifting as well as resisting up shifting when it senses a extra load.

 

[panchothedog]

If you're going to open it up to replace the springs, might as well put in the lighter weights as well. They will have as much affect as the springs. Double the difference, same amount of work. About $ 17. Cheap results.