"Constantly blowing clutch bearings? It can be a tough problem to eliminate.
Here are the most common causes & solutions

Is the clutch overheating due to slippage? If the shoes are worn, or if your springs are too stiff or if you've gotten oil or grease in the bell, you could get slippage. in that case the shoes are not engaging properly and slipping. this causes the bell to heat up excessively. This heat can/will destroy the bearings quickly! The solution is to clean the bell and or replace the shoes. If the spring is too stiff you might try a weaker spring.

One of the most common causes of clutch bearing failure is improper lubrication. Soaking them in any type of oil is a mistake. Once it heats up the oil migrates down the shaft into the clutch = heat = toasted bearings. Use a high melt temp extreme pressure grease in all the sealed bearings. This grease is designed for extreme bearing applications and does not migrate at operating temperatures. Many racers also have success cleaning all the lube out of the clutch bearings then re-oiling with one-half to one drop of Mobil 1/Prolong/etc.

Is the clutch bell hitting the chassis when it flexes? Look closely directly under the bell for a rub mark. If it comes in contact with the chassis at all this can cause blown bearings. The solution here is to use better braces to keep the chassis from flexing. If this isn't possible or a quick fix is needed at the track shims/washers can also be used to raise the entire engine assembly a little.

Is the clutch assembly getting too hot? Many clutch bells turn into a blue color instead of normal black when overheated. If one is available use a temp gun at the end of a hard run. An excessive temperature at the front of the bell indicates resistance or a vibration problem. At installation the bell should spin completely free and there should be a little "play" (about 0.5 mm). This allows the parts to expand when they heat up without binding. Other possible causes of excessive heat are a clutch spring that has become weak (allowing one shoe to constantly drag) or a worn or broken clutch shoe.
Check both engine bearings. Play in either will cause clutch bearing wear by allowing the crankshaft to vibrate at high RPMs. If the front engine bearing leaks fuel this can migrate into the clutch causing the failure.

A slightly warped crankshaft can also vibrate clutch bearings to death quickly. This is the most difficult problem to run down since the shaft does not have to be noticeably warped to cause bearing damaging vibration at high RPM.

The clutch bell itself can also be a bearing eater if it has developed an out-of-round (warped) condition or has been manufactured out-of-tolerance. I've seen some famous brand bells with this problem right out of the package. The outer bell spins perfectly round but the inner bell (with the teeth) is warped."