Duromax 440 Mods, Sprocket Ratio, & Torque Converter Springs?

[Econdron]

I would really like to avoid a lot of trial and error with this build, but we are building a larger version of the Grand Daddy go kart. It will have 20" rear tires, a Duromax 440 CC engine, and 40 series torque converter. I currently have a 60T sprocket planned for use with the rear wheels. So I have a 3 part question:

1) I was originally planning on installing just the stock engine and doing the mods later if I felt it needed it, but after reading some posts it seems like it makes a significant enough difference where I should just do it before installing everything. Can anyone please give me as detailed a list as possible of the necessary parts? Or where I can find more info on which parts should be replaced and how I can figure out which parts are compatible?

2) For the torque converter, I've read about replacing the springs. It seems these are color coded to indicate stiffness? How do I know which springs I should use, and are there any recommendations for the setup I specified above?

3) Regarding the sprocket tooth ratio, I believe as it currently stands I'm on the low end of the ratio. I've read that ratios of 1:6 to 1:8 should be used for 20" tires and I believe I'm currently at 1:5. I'm not positive it works this way, but the sprocket on the torque converter looks like it has 12T. Should I go with a 72T sprocket, or use a jackshaft to get a higher ratio? Or is the 60T fine?

 

[redflash]

It's easier to go to a 10 tooth on your tc drive sprocket....and cheaper too !

Da redflash

 

[panchothedog]

On the 40 series the selection of springs is not as great as the 30 series. For the driven clutch you might have to install the reverse wound spring. Depends on if
you use a plate system or a free standing jack shaft where you can flip the clutch 180. For the driver you can install lighter weights and stronger springs. This will increase engagement RPM about 1000, and will get the engine into the upper rpm range real quick. I only see one selection of each for the 40 series.
Don't install those on a governed engine as it won't be able to rev high enough to get into the higher gear range. As far as hop-up parts, same as any ICE. Higher compression ratio, higher lift and longer duration cam, stiffer valve springs, header pipe exhaust and less restrictive air filter with a bigger carburetor jet, or a bigger carburetor.

 

[panchothedog]

As redflash says, 10 tooth drive sprocket and a 60 tooth axle sprocket is a proven winning set-up.

 

[Econdron]

Oh duh. I don't know why I didn't think of that!

Looks like the stage 2 kit plus some of the extras is easily going to cost $800+, so I think I'll check the performance of the stock engine first, and go from there.

What exactly is the purpose of different stiffness springs on the torque converter? Does it change performance, or is it just a change in throttle response to acceleration?

 

[panchothedog]

No doubt about it, the hop-up stuff for the bigger engines is a LOT more expensive than the little ones. Your question about the springs, the answers are yes and yes. You have to rev the engine higher to get the kart moving. But then the whole shifting process from low to high range takes place at an elevated rpm. If you are running a modified or even UNgoverned engine capable of spinning 5000 to 6000 rpm this will allow the engine to get into that rpm range much quicker. On my kart it actually felt like a 2 or 3 horse power boost after installing the lighter weights and stronger springs. The higher RPM range is where the horse power lives. This just helps it get there.

 

[Big Bob]

Go Power Sports sells a kit that uses medium weight rollers (SKU:KD203649A), heavier duty red springs (SKU:KD203040A). and a stiffer green spring (SKU: 203039A) to open the pulley. This moves the engagement RPM from around 1600 to 2600. I put it on mine, but haven't had time to try it out yet.
Medium Weight Cam Rollers for 40 Series Driver - GoPowerSports.com
Red Upgraded Spring For 40 Series Driver - GoPowerSports.com
40 Series Driver Compression Spring - GoPowerSports.com

I have the GPS TAV which is a Comet unit. Taking it apart and changing this stuff is pretty simple. It you go to YouTube you will see guys cutting the welds on the large nut so they can take it apart. You don't need to cut the nut! Make sure you have a spray can of dry graphite before you do this job.