720 motor: How many total cageless piston needle bearing should i have had????

[vallentinerocks]

I believe I may have figured out what damaged the new top end rebuild I had done. But need to verify how many cageless needle bearings i should have found total upon removal of old pistons.

the previous owner had cageless needle bearings installed for the pistons. of course these fell at out and we had to fish out the bearings. Possiblility looks like we didnt get them all out of the cylinder and a needle bearing got injected into the chamber upon starting attempts causing new head surface and top of piston pit damage then leading to the sleeve and ring damage. one pit in the head surface is exactly round and fits the end of a loose needle bearing.

Anyone know how many total needle bearings should have been recovered on a 720 single carb for 98 GTS? the top end kit we replace it with had he caged bearings and they fit fine.

 

[ocod]

I think its 34 pins from I found online

 

[vallentinerocks]

anyone know for sure? i dont know how many variance in diameter bearing sizes and number of bearings it leads to... so far i have found it might be 36 and now 34 total..... we thought it was only 28 when we fished them out. and new bearings i believe he counted 28 total and he thought he had them all . well....... i recounted the old free needle bearings again and we have 29.... an odd number. just want to know how many we might have in there so this dont happen again.

 

[hackete]

It's 34 I just went in our shed and counted. I put a top end kit on son's 95 XP a few weekends ago and left them in the old pistons. Both pistons had 34 in them and I was extra carefull taking them off.


This was on a 95 XP 717/720 engine.

 

[vallentinerocks]

99% sure based on evidenence of damage to rings, piston, cylinder wall, etc... that it was a rogue needle bearing that fired around the chamber that we did not recover. plus i found a round piece of what was a needle bearing still sitting on top of the piston. all the damage is round and the diameter of a needle bearing.... anyways...... not sure of the 34 total and variance of diameter thickness, but i have now recovered a total of 38 if including one that got away...... anyone heard of 38 total cageless needle bearings?? ive shaken, stired , swished, magneted and blew air into the motor where we fished the fallen needle bearings and i dont see anything else... i think its clear now..... well im hoping... doing a new cylinder next week (again)...

 

[ocod]

why not just split the case and do it right??