Rotax Front Driver Questions from a Newbie

[Ambrose Buldo]

My friend just picked up an '08 Rotax Kart... He is running 13/88 Gearing. He needs to pick up a rew more RPM at end of straight and exiting corners, thus wanted to go up a tooth or two.

However, if he goes any larger then 88, the rear sprocket will be to close to the ground. He wants to change to a 12 front driver. Is ther anyting special he needs to know before ordering this? Are there differant style front drivers based on year of engine? Is there anyting else he should be ordering.changing at the same time? Washers, bearings, etc?

He runs a Panther chain, 219 pitch.

Any special tools needed?
_________________
Ambrose Buldo - AKA Racer27
Old Tappan, NJ 07675
Current: Citation FC2000 (For Sale), Madza RX8, VW Eos
Kart for myself: Intrepid Silverstone Pro w/HPV3 --- With a ROK TAG engine waiting in wings
Kart for Daughter: 2001 Birel ARC-100

[tony zambos]

I'll take a whack at this. Your fiends current gear ratio is 6.769 with the 13/88 gears. Going to a 12 tooth gear on the engine, the equivalent gearing would be 12/81 (6.750). This is going to give you some room to added teeth again to the axle. See what the other guys in your class are running.

Engine sprockets from 12 teeth and up use the same needle bearing. So switching from a 13 to 12t will not be an issue. You can re-use the same bearing. The 11t sprockets use a thrust washer if you're thinking of go this route. When ordering a new 11t, order the bearing to go with.

To remove the clutch, you'll need a 17mm socket and something to stop the crankshaft from rotating. The something could be a flat blade screw driver, a piston stop or a fixation tool. My opinion is the fixation tool is the only way to go.

Next you have to get the sprocket off the clutch drum. There are two Rotax tools to hold either the drum (pre-09) that has holes in it or the sprocket if its a drum without the holes. Get the tool that matches your clutch type. To get the nut that holds the sprocket to the drum, you'll need an 1.5 in socket and a breaker bar. Found my 1.5 at an Autozone store. The nut is very shallow. The socket comes with a rounded shoulder. Have the socket cut flat so you don't destroy the nut.

The sprocket is pinned but and pin could fall out once the nut is loose so be carefull. Replace the sprocket and put a dab of Loctite on its threads. Grease the bearing and assemble in reverse order. The sprocket nut should be torqued to 100 nm and the nut on the crankshaft gets torqued to 60 nm

Again, check with the guys at the track you race with. Someone may have the tools and willing to lend a hand. Or you could get to know your local kart shop owner and have him swap the sprockets.
_________________
tony zambos
ap kart racing
L.A.D Specialties

[Chris McGinley]

[tony zambos]

Chris

Thanks for the clutch torque spec update.
_________________
tony zambos
ap kart racing
L.A.D Specialties

[Ambrose Buldo]

Thanks for he feedback... Looks like he has the older clutch. I'll have my friend order the parts today as well as an assortment of sprockets.

Related question - After making the change, the chain is going to be too long, thus needs to be shortened. Can a Panther Chain be resized using a regular non-o-ring 219 tool? I resize the chain on my KPV all the time but it is a standard chain, not a Panther.

Thanks in advance.
_________________
Ambrose Buldo - AKA Racer27
Old Tappan, NJ 07675
Current: Citation FC2000 (For Sale), Madza RX8, VW Eos
Kart for myself: Intrepid Silverstone Pro w/HPV3 --- With a ROK TAG engine waiting in wings
Kart for Daughter: 2001 Birel ARC-100

[tony zambos]

Panther chain can be re-sized, but you'll need the Panther tool to open the chain up and new links to close it back up. Panther does not recommend re-using links.

Link to Panther re-sizing video: http://www.pantherchains.com/technical/sizing219classic/
_________________
tony zambos
ap kart racing
L.A.D Specialties