Rave valve broke howwww

[Runner001]

98 speedster twin 110 both ran great went fire up weeks ago and got a clunk , ended up pulling heads and seen chunks of metal jammed in the piston . So got top end off and seen pieces in the. Crankcase so all at this time i didnt know where the chunks came from so i figured something in the crank so stripped it down piece by piece and pulled whole enginr and even split crank case too my suprize nothing broke so after my days days of examining EVERY PART OVER OVER FOR THE BROKEN PART OF WHSTEVER . I ended up puzzeled and found NOTHING AND FED UP SO WHILE MY WHOLE ENGINE AND EXHAUST WAS IN MILLION PIECES ON GARAGE FLOOR I GAVE UP AND decided might well clean up the extermal parts that were good too be put back together and first thing i decided too take on was cleaning the rave valves ( the first things i pulled from engine with the plugs ) and just put them aside away from everything . Anyway too my supeize i didnt notice when i pulled them out from engine DUE TOO THE BLACK GRIME ALL OVER THEM that The FRONT valve was shorter than the other and UPON CLOSER LOOK THIS IS WHAT I FOUND that the top portion of the valve was broke clean off and also the vave cap threads ( top bellow ) were completely screwed and tore too pieces . AND SORRY FOR THE LONG DETAILED POST BUT IT REALLY PISSED ME OFF THAT SOMETING LIKE THIS CAN COMPLETELY DESTROY MY SUMMER AND NOW HAVING TOO REBUILD COMPKETE ENGINE . So my only question IS for anyone that can help

WHY THE HELL DID THIS HAPPEN , whst ARE POSIBLE CAUSES OR THE VALVE JUST BREAKING OFF LIKE THAT

THESE DNGINES WERE BOTH REBUILT TWO YEARS AGO TOP TOO BOTTOM.

Here is pic of the headach thanks

 

[robomatic12]

Are those OEM valves, or SBT replacement valves? I would inspect the other one for cracks. Is this engine rebuilt?

 

[Runner001]

Yes the both engines were said too habe been rebuilt top too bottom two years ago from prev owner . Also by my searching on valves these look like the newer valves and not the older factory ones due too the grooves in them . Also that piston has scoring up the side of it as well but not damages too anything but that i just bought boat 6 weeks ago ran perfect all times i had it out no issues as all and my last run was great than i pulled out water parked it in driveway for bout 3 days than went too do my pre trip for that evening fired port engine fune and went fire SB AND I GOT A 1/4 crank and than CLANK so i was like WTF . So figured was starter motor but as i started tare down i seen the chunks so its weird cause it ran fine on last trip which was about 2 hours o the water cruising at 5500 rpm doing prob 50 kmph and than drove it on trailor and sat it in driveway for few days and than all sudden this happens in yard. Seee when i bought boat i changed pkugs sbd stuff but didnt insect the valvs at all .

 

[Seadoodoc]

At the risk sounding like a know it all , 25 yrs on these damn mtrs has given me some pretty solid historical data. Initial valves were stamped 351. Breakage problems . Later stamped 352.. Upon boring any SD mtr over 0.25 involves grinding that valve back for proper piston and ring clearance. So if motor is bored out at .5 or 1 mm over the rave valve should have been ground to a bit of a flat surface on the knife edge rather than be a knife edge. I typically do this in about 10 seconds and a belt sander. Lastly.. If something else let loose in the motor the valve potentially could have been just residual damage. We lost a circlip on a motor yesterday and created huge Carnage.

 

[Chester]

It's common for the RAVE valves to break like that on the boats. I believe it's from vibration at a certain RPM. Replace the valves and fix the other damage and you're good to go.

Chester

 

[Danosll]

2 things to look for wear in the actual rave valve slot or bore or wear at contact point of valve to cylinder which will allow valve to touch piston