Procat belt adjustment

[AndyF]

Hi,

I have an old Procat that I used to race and got back running not so long back. It is virtually a std car except for kyosho gold shocks.

I can't get the belt to stay in the middle of the front diff pully. Everytime I adjust it with those screws at the front it either shoots off to the right or to the left. When I raced it many many moons ago I don't remember having these issue. Any ideas?

[brian s]

this was a problem with the original pulley with the belt running to one side or the other, if tensioned correctly though it should run in the centre when under power. most who ran cats upgraded to mms diffs.

[QuackingPlums]

There is very little 'yaw' effect to be gained by adjusting the screws - as long as the belt is tensioned correctly and the gearboxes secured (the straight-through nut and bolt mod is useful here) then the belt will run true under load.
I ran the smaller overdrive diff in mine rather than the MMS and it was fine. At idle the belt always sat to one side...

[AndyF]

I noticed some pics of procats with bolts all the way through. I will have to give that a try.

The pully looks higher in the middle than the two edges, so once it starts to go it hasn't much chance of getting back up. It was 20 years ago that I last used it, I can't remember if thats how it started life.

[QuackingPlums]

Yeah, that's how they always were. I never understood the principle behind it either but I remember that when the belt was correctly tensioned then I could see it move up to the middle of the pulley even if I just raised the car up and throttled up.
I assume you remembered to loosen the bolts before tightening the tensioning screws - otherwise you'll just bend the bar that goes through the front transmission housing! :lol:
Also check out Luke's thread here (http://www.oople.com/forums/showthread.php?t=48668). He has lots of pics and detail about how he modded the front gearbox with the bolts and spacers to help tension the belt. I know he's got the MMS diff but the mod works all the same.

[brian s]

changing from the self tapping screws is easy and does not require any stripping down.
get some 3mm x 40mm csk head screws and nuts(ebay).
remove one of the self tapping screws and drill a 3mm hole half way through, leave the drill in positition while removing opposite screw and then complete drilling right through (just ensure the `L`shaped front suspension brackets do not move while you drill through) . fit 40mm csk head screw and nut then move on to the next one.

[kaszal]

Also check out Luke's thread here (http://www.oople.com/forums/showthread.php?t=48668). He has lots of pics and detail about how he modded the front gearbox with the bolts and spacers to help tension the belt. I know he's got the MMS diff but the mod works all the same.

You can see the spacers clearly on page 5 post 97

http://www.oople.com/forums/showpost.php?p=494041&postcount=97

Hi Eric... use the Force

[AndyF]

Well, I might have found my problem. Decided to do the bolt mod on the front. When I took the bumper off I discovered that the one of the two parts that make up the frame that the crash back hinge attaches to and that clamps the front gearbox was broken.

I'm not holding out much hope on finding spare! Try superglue tonight!

[brian s]

let me know which one is broken and i`ll see if i have one.