Ideas Please!!

[JohnPZX]

I have a '97 2.6 ProV with a HT Phase II kit. Last year I blew #5 Piston - I had the motor re-built and that port re-worked to a little over. I went through break in and had about 3 hours of run time afterword on it and look out - blew #5 piston AGAIN!! Carbs were rebuilt as well.... any initial ideas on why that piston would fail AGAIN???

[gamblerjewell]

how did the piston fail? Burn, Break, melt down??????

[JohnPZX]

Not sure... it was broken up.

[Mat_HT]

Was the original cause of failure ever determined?
Do you have any pictures of the blown up cylinder? That will tell us a lot about the type of failure.

[JohnPZX]

Don't know that they actually determined that... Here are the pics the first time it went

http://www2.snapfish.com/slide...87984/

http://www2.snapfish.com/slide...87984/

[rangerguy]

Like I said in you first post in the Yamaha Motor section, if they didn't fix what caused the first one to blow, then the problem was still there and caused the second #5 to blow. If you rebuild it again and don't fix the problem, then #5 will blow again as someone above me stated. Check, cooling system, injectors, coil, ect, just to many things to check and a good re-builder will know what to check.

[DoktorC]

Kinda looks lean...blew the exhaust side off the piston then caught/broke the ring (which made all the marks in the head/piston top). I'd be checking your bottom carb for dirt/water and anything that would cause an air leak (bleed hoses)....