DS w/ a 420 predator. Clutch questions.

[Phillip Drums]

I'm working on a 90 DS for a friend. It already had a predator 420 swap done, but I don't think there was any clutch mods done. It only runs out at 14-15mph. Any suggestions on a good clutch set up? Engine runs out fine, but after half throttle there's no more speed.

[CP241]

Putting a big motor in a golf cart alone will not increase speed. We need more information to determine if that’s correct or not. How the throttle is set up, condition of the belt, etc. if the engine is mounted a little too far backwards there won’t be enough tension when it’s running and it won’t pull the belt to the center of the driven clutch (losing speed). Put it in neutral and rev the engine. While it’s spinning fast the belt should rise to the top of the front clutch, and should drop all the way down to the center of the rear clutch.

You have to keep in mind. Stock golf carts with governor maxed will run around 18mph before hitting the rev limiter. A bigger engine will give more power to climb hills and sloppy mud, but it doesn’t spin any faster (RPM) than a stock motor so it’s not going to go any faster. Gear ratios increase speed. Cheapest is bigger tires but a gear kit 8:1 would be good on a 420 and add a lot of speed.

[Phillip Drums]

Originally Posted by CP241

Putting a big motor in a golf cart alone will not increase speed. We need more information to determine if that’s correct or not. How the throttle is set up, condition of the belt, etc. if the engine is mounted a little too far backwards there won’t be enough tension when it’s running and it won’t pull the belt to the center of the driven clutch (losing speed). Put it in neutral and rev the engine. While it’s spinning fast the belt should rise to the top of the front clutch, and should drop all the way down to the center of the rear clutch.

You have to keep in mind. Stock golf carts with governor maxed will run around 18mph before hitting the rev limiter. A bigger engine will give more power to climb hills and sloppy mud, but it doesn’t spin any faster (RPM) than a stock motor so it’s not going to go any faster. Gear ratios increase speed. Cheapest is bigger tires but a gear kit 8:1 would be good on a 420 and add a lot of speed.

I'm not sure of the belt condition, I don't know what the club car belts are supposed to measure out at. Do you know what the width is supposed to be? I can check it when I find that out. The throttle cable is run from the carb to the box, the stock rev limiter is deleted. I was looking at the clutch action yesterday, I did notice it goes all the way to the top of the primary, it looks like it's not quite going all the way down in the secondary. It runs down in the secondary pretty quick then stays at that point (I will verify if it's going down all the way). The reason I mention speed is because it accelerates nicely and then about half throttle just hits the wall, (no more speed, but motor revs up more). I know you need to do clutch work after changing to the bigger motor, that's why I was asking if there's a certain combo or clutch that seems to work well with a 420. I'm new to the 420 and club cars so not sure if the clutches are bone stock or not.

[Phillip Drums]

The belt is not going all the way down in the secondary clutch. It's going a little over half way down the sheaves.

[CP241]

There’s part of your problem. Do the sheaves look wavy on the driven clutch? It may be worn. That will improve performance and gain a few mph.

Is the cart lifted with larger tires, or stock?

[Fairtax4me]

Do you have a picture of the clutches?
The belt will not go all the way down in the secondary. It will only go as low as the innermost diameter of the cones, so maybe 1-1/2 to 2”.
A worn out or incorrect belt would cause it to not go even that far.

The best way to spot a worn belt is if it sits down between the sheaves of the secondary clutch. The top of the belt should stick up above the outer edge of the clutch. If it’s below the edge of the clutch it’s worn and should probably be replaced.

[Phillip Drums]

Originally Posted by CP241

There’s part of your problem. Do the sheaves look wavy on the driven clutch? It may be worn. That will improve performance and gain a few mph.

Is the cart lifted with larger tires, or stock?

The cart is on 18" (stock size) tires. I couldn't see if the sheaves were wavy, I will get a better light in there and inspect that. I did find the stock belt measurements and the width is worn down about an 1/8"

[Phillip Drums]

Originally Posted by Fairtax4me

Do you have a picture of the clutches?
The belt will not go all the way down in the secondary. It will only go as low as the innermost diameter of the cones, so maybe 1-1/2 to 2”.
A worn out or incorrect belt would cause it to not go even that far.

The best way to spot a worn belt is if it sits down between the sheaves of the secondary clutch. The top of the belt should stick up above the outer edge of the clutch. If it’s below the edge of the clutch it’s worn and should probably be replaced.

I found belt specs, according to those this belt is worn down about an 1/8". Which would explain a bit. It does sit down in the sheaves instead of sticking up a bit. And as I found out on my Yamaha that is a bunch of wear on a belt.

[CP241]

Correct that belt is worn. It’s also possible the clutches are worn.

The only “upgrades” really necessary are to the primary clutch if you want it to idle. Sometimes the stock clutch will close at too low of an rpm and it will creep at idle. But that’s about it, otherwise the stock clutches should be fine on a 420

And just to set expectations, I’d expect around 15-18mph with the 420 on stock tires and no other mods. It’ll get to that speed faster than a stock cart would but since it’s not spinning any faster than a stock motor the overall top speed remains the same. But the 420 will respond much better to lift and big tires than a stock cart would since it’s got plenty of power to make up the difference from the rotational mass and gearing changes that result from a larger tire.

[Phillip Drums]

Originally Posted by CP241

Correct that belt is worn. It’s also possible the clutches are worn.

The only “upgrades” really necessary are to the primary clutch if you want it to idle. Sometimes the stock clutch will close at too low of an rpm and it will creep at idle. But that’s about it, otherwise the stock clutches should be fine on a 420

And just to set expectations, I’d expect around 15-18mph with the 420 on stock tires and no other mods. It’ll get to that speed faster than a stock cart would but since it’s not spinning any faster than a stock motor the overall top speed remains the same. But the 420 will respond much better to lift and big tires than a stock cart would since it’s got plenty of power to make up the difference from the rotational mass and gearing changes that result from a larger tire.

That all makes perfect sense! Thank you! I'm going to start with a new belt, and some carb adjustments, I'm not entirely sure it's getting full throttle, and check for clutch wear. I think we'll grab a little gain there.