Beta Mini Trial 50

snowy · Post by **snowy** » Sun Jan 01, 2006 7:23 pm

I have just bought a 1994 Beta Mini-trial 50.

Does anyone have some any idea how I can give it a bit more grunt?
I've heard that a 78-rear tooth sprocket might do the job.
Any help would be great.

Regards
Snowy

Post by **David Lahey** » Mon Jan 02, 2006 8:04 am

Some friends of mine just bought a Beta REV50 and it has been modded to improve performance in sections. I have no idea if the Beta mini trial uses the same power unit but here is what was done to theirs:
Huge rear sprocket - almost the size of the rim.
Centrifugal clutch springs modified to increase the RPM at which the clutch starts to drive.

Rob W · Post by **Rob W** » Mon Jan 02, 2006 12:03 pm

Snowy, just about all the minitrials I have seen have a huge rear sprocket fitted. As David says, fit stronger springs to the centrifugal clutch so it engages at higher RPM. The idle screw can then be turned in to increase the idle speed and reduce stalling. The lower gearing helps preserve the clutch pads, but lightly buffing them also helps to make it grab.

Hey David, if your mates 50 has a centrifugal clutch then it is the "minitrial". The Rev50 is a water cooled 4 speed with a manual clutch.

Post by **David Lahey** » Mon Jan 02, 2006 3:04 pm

Rob W wrote:Hey David, if your mates 50 has a centrifugal clutch then it is the "minitrial". The Rev50 is a water cooled 4 speed with a manual clutch.

Thanks Rob
I've just sent myself back to Beta school (Kal's website) and can tell the difference now.
Sorry Snowy. If you want I'll send you a PM or an email with the contact details for the people who have the Beta Minitrial.
David

KTMSprocket · Post by **KTMSprocket** » Mon Jan 02, 2006 4:37 pm

In the three shoe clutch KTM engine used in the modern Betas you can use coils with shims to alter the revs at which the clutch stalls, or you can use cupped spring washers (known as a stack) which are shaped like a "(" with flat shims added to alter the stall speed. These two methods are valid and have diferent effects on the clutch take-up.
The cupped washers can be assembled ( or (( or () or (()) and so on to get desired hit of the clutch.
The coil springs are from the KTM Mini Adventure and the cupped washers are used in the KTM Pro Seniors bikes.
if you want a snappy clutch, go with cupped washers, if you want a smooth take-off go with the coil springs.