World Formula engagement issue

Chris Dorsey · Joined: 01 Dec 2010 Posts: 14

I've been having trouble with my daughter's World Formula and need some help from the experts. On take-off, under load, there is an intermittent grinding sound as the kart accelerates. During this time, the kart loses drive and then lunges forward, almost like the clutch is engaging/disengaging. The problem seems to go away once she is up to speed. I tried a new clutch and cleaning/rebuilding another clutch and the problem did not go away. I'm wondering if the problem is in the pull-start/recoil or starter units, but I'm just not sure where to start.

I would appreciate any help!

Larry Andrews · Posted: Sat May 12, 2012 10:39 pm Post subject:

I had this problem once with a 13t #35 sprocket. Some of the smaller sprockets use thin bushings instead of needle bearings and do that when they lose lubrication and start galling. Some moly might fix it temporarily. New sprocket/bushing usually fixes it permanently.

It's not likely that the recoil starter is involved if it still works properly. The ears pop out when you pull the handle and retract afterwards - if they were stuck then it seems like there'd be a big mess and a non-running engine.

David McDowell · Posted: Sun May 13, 2012 9:15 pm Post subject:

How do you have the clutch installed inboard or outboard, if outboard did you turn the shoes around since the clutch comes stock for a inboard configuration. I experienced the same jerky sensation until up to speed and the clutch fully engaged before I turned the shoes around.

Ron Carello · Posted: Wed May 23, 2012 3:01 pm Post subject:

Dean Graves · Posted: Wed May 23, 2012 3:15 pm Post subject:

Interesting, in the past I've ran the clutch with yellow springs and ran inboard with the hub both ways. I found the hub configured outboard but running the clutch inboard ran very smooth.

Bernie Lacotta · Joined: 21 Mar 2006 Posts: 168

David Klaus · Joined: 25 Mar 2009 Posts: 31

Chris,
I thing that you might look at to look is lower engagement springs. It sounds like the chatter you are experiencing is the clutch slipping while trying to engage. If you are on a tight track the engine rpm could be causing the clutch to go in and out of engagement.

Another option that Bernie describes is running the cartridge backwards so the shoes fight against the angle ofthe ramps while engaging. This will soften the engagement. It sounds like Bernie didn't have a positive experience trying this but a lot of our European community changes the springs AND flips the cartridge. Together these changes seem to be readily accepted.

You can run this clutch inboard. We don't suggest this simply because too many forget to use the radius washer and the force of locking the clutch down forces the assembly into the radius at the shoulder of the crankshaft causing the gear hub to possibly fracture. With this engine raced around the world this suggestion is to help eleviate a common error that costs racers unnecassary money. Done correctly you shouldn't have any issues.