Need Advice

[Jwarren357]

Hi i have recently completed an off road build and i am really having issues.
I have a fox vortex cart that i have adapted a 670 predator engine to. I am running 18.5x9 tires and a 60 tooth rear sprocket on #40 chain.
The issue i am having is with the torque converter up belts. It is the 780 kit from GPS and has the correct 5/8 back spacing on drive clutch. Right now the gear ratio is 6:1 and it is slipping the belt after about 2 hours. The first belt was due to incorrect spacer sent with kit. Gps being the awesome group they are sent me a new spacer and belt and told me to go to a 60 tooth rear sprocket.
My question is, do i need to change my gearing
The cart weighs about 450 pounds and i way 220 and my brother weights 150. The engine has basic mods from performance 670 and an exhaust.
Any help would be greatly appreciated

---------- Post added at 08:20 PM ---------- Previous post was at 08:18 PM ----------

At 60 dollars a belt i cant really afford that every ride. we do go up hills but they are not super step. The rpm runs around 3900 at governor

 

[Jwarren357]

This is the kart i am working on

 

[landuse]

I would hazard a guess and say that you are still geared too high for the weight of the kart as well as the tire size. This will cause premature belt wear. 6:1 sounds VERY borderline for what you have

 

[Jwarren357]

Any recommendations on what i should go with.
My only option is a jackshaft but space is and issue

 

[anickode]

Any recommendations on what i should go with.
My only option is a jackshaft but space is and issue

That secondary clutch should really be turned around. The backplate setup is really a **** poor design for any symmetrical clutch setup. Watch it shift while up on jackstands. It pulls the belt WAY out of alignment, because the primary pulls the belt IN while the secondary pulls the belt OUT. It really quite bothers me that they even sell them this way. It's easy, but wrong.

Gearing is probably an issue too, as mentioned, for a buggy that heavy. Is there not a bigger sprocket available? You said GPS told you to go to a 60t, but also said you are running a 60t. Typo? It looks like there's room to fit at least a 72t in there if that's the 60 in the pic.

 

[Jwarren357]

Unfortunately for the wheel clearance and manco hex axle type,a 60 is as big as the offer and i can fit, the chain is pretty close to the ground
I was wondering about the back plate causing issues
So the secondary clutch needs to be the other way that way they both open and close in the same direction
I guess it sells belts lol
I may look into doing a different set up and putting secondary on jackshaft then a second jackshaft to change gearing
I looked at going back to a 54 tooth then using a 12 and 17 sprocket on a jackshaft which will land me arounf 9.18:1 gearing

---------- Post added at 10:20 AM ---------- Previous post was at 10:16 AM ----------

Basically a 10 driving a 17 and then the 12 driving the 54

---------- Post added at 10:22 AM ---------- Previous post was at 10:20 AM ----------

I could also just have an 8 tooth sprocket and have a 7.5:1

 

[Brianator]

It's not advisable to run a sprocket smaller than 10t (#40 chain) unless necessary, not only is it going to wear out quick but it's really hard on the chain to make that sharp bend. Thats my 2 cents!

 

[anickode]

It's not advisable to run a sprocket smaller than 10t (#40 chain) unless necessary, not only is it going to wear out quick but it's really hard on the chain to make that sharp bend. Thats my 2 cents!

Plus the bore wall gets really thin below 10 teeth, especially at the keyway. Under the strain of a 670 with a torque converter, you'd be asking for a failure.

 

[Brianator]

Good point about the wall thickness!

 

[landuse]

Another solution would be to get smaller tyres... *shrug*