Weird ZA50 Failure

I had a weird failure with my ZA50 motor this weekend.  After a hard night pushing the limits of our bikes with Soma-san on Japanese Hwys 129 and 246, I rode my bike the next morning to a rude awakening.  When I was at half throttle, my engine started to make a violent shaking sound.  I immediately thought it was the Gila's death rattle of seizure!!  But soon realized I heard this sound before.  I next thought it was my clutches blowing up.  In any case, I was lucky to make it home on 1/4 throttle.




I first drained and inspected the transmission oil.  It was pretty black but I saw no clutch or gear fragments.  That was a good sign.  Then, I stripped down the transmission and inspected my clutch.  It was still intact with typical Gila cutch wear and tear.  So I started to worry and thought if it was my Gila seizing up!!

I inspected the rest of the transmission and discovered the culprit!!  It was the first speed gear roller assembly.  For some reason, all the retainer springs that supposed to hold the roller bearings in place were all dislodged and bunched up in one area of the gear.  The roller bearings itself were in-place but "floating" around the nut causing the gear to come out of tolerance.  I'm surprised that none of the bearings didn't displace and fly into the transmission.

What to do...

...WTF!!

After further breakdown, all the spring retainers were either all bent out of shape, torn up, or broken.  The bearings and gear seem to be OK.

Freakin Crap!!

This type of failure never happened to me before.  I checked Moped Army forums if this was a common occurrence.  No post about this situation.  So I started a post on there to see what's up.  I thought I was sh!t out of luck with replacing these springs and that I would need to find a whole first gear replacement.  Searched on TreatsHQ and to my relief, they sell it used for cheap!!  THANK THE MOPED GODS!!!

As far as future prevention, a person on post suggested it could be a shimming problem.  I'll definitely look into the tolerances when I rebuild it.  If anybody has other suggestions, please leave me a comment.  I will follow up on the rebuild later.

UPDATE:  Found the culprit.  The first gear roller plate was loose.  See red box:

Crap!! Crap!!

The roller plate backed out which caused the retainer springs to dislodge.  All the springs spun around and got all bunched up in one location of the roller gear due to the centrifugal force.  I must not have put it on back securely when I removed it during my overhauled of the motor back when I got to Japan.  Also, I could of damaged it when, I was wrestling to remove the reverse nut when I redid my clutches.  In any case, I discovered it when I ran the bike the other day and heard the same clunky sound.  When I opened up the transmission, I notice the plate lifting from the roller gear and the retainer springs ready to come out again.  The plate could easily be removed by hand!!

SOLUTION:  Reshaped the plate a little with a mallet and snapped it hard back into place.  Now it needs to be pried off to remove it.

UP-UPDATE:  The plate backed out again!!!  I was riding and got the death rattle and shakes.  I barely made it back home.  I had to try to keep it in 2nd gear which means I had to speed home.  Opened it up and saw some of the retainer springs were ready to pop out because of that damn plate.

SECOND SOLUTION:  Reshaped the plate and put some red loctite on it.  Not sure this is gonna work but this my last hope other than replacing the whole first gear...

On second thought, because I have a high revving high speed motor, I'm going to just replace the whole first gear.  I think my 'Second Solution' would work on a stock set up but not a kitted one.  I just don't want to take a chance!!!

More updates soon to come...