Had the front stat gear on my 12A road race motor fail on me - engine lost power while on track, really not much drama - felt it like it lost an apex seal.



This is a rebuild with about 6 weekends on it. I inspected everything during assembly and did not see any damage or cracks to the stat gears.



The only odd thing I had during the rebuild was that I had a little trouble getting a consistent endplay measurement.



So I have a few questions:



1. Is this just bad luck, or is there something that I could have done during the rebuild to cause this?

2. Anybody have info on why this type of failure occurs??

3. There was debris in the oil pan, but the all the bearings look fine, do I need to worry about trash in the oil system killiing my next rebuild? Do I need to replace the oil cooler? It seems like this failure produced big chunks that should not make it past the filter - or is that just wishful thinking?

4. One tip of the front rotor looks like it contacted the rotor housing - the apex seal was stuck in the groove. The rotor housing looks fine. I guess the missing gear pieces caused that?



I'll try to post some pics up.



Thanks,

Neil

1. i'm thinking bad luck, usually the gears look great



2. too much rpm! i see the failure when the driver tries to get 4th gear but gets 2nd instead



3. you might wanna try flushing the cooler, although i think the big chunks are in the pickup screen



4. yep, gear locates the rotor...

Thanks.



Does anybody use UV dye to check gears before a build? Motor saw 8500 rpm regularly, maybe a few times up to 9k, but never had this failure before with other motors. I can get hardened gears, but I didn't think it was really needed for a stock port motor turning roughly 8.5k max



Anybody ever try to open an apex seal groove back to spec? I guess I'd have to swap in a new rotor gear as well.

ive never checked a gear like that, might not be a bad idea. its not a huge problem, ie 8500rpm seems ok, but i guess you just got lucky



i know people who have opened and close apex seal slots, the really important thing is the corner seal, if thats off, i think you're done. obviously a little tweak is going to work better than straightening out some big dents