what would have caused this to happen?
 

ok long story short bike was running good with 29K on motor, spark plug shot out the head and stripped the hole, dont like helicoils so i bought a used head, a shop checked it and reseat valves and everythnig put the new head on and 15 miles later after i pay the 684 dollar bill the top end starts ticking like crazy, shop says its nothnig they did, there say it might be due to low oil pressure which is bs and or cam chain tensioner, so started bike bike ticked and then shut off and died, took valve cover off both right side intake valves wont go back up i believe piston stuck them thats wy it wont start.., spark plug is smashed looks like a valve hit it and also looks like piston damage, i have not removed the head yet, and the cam chain is so tight its rediculous, what could have caused this did the shop mess somethnig up? give me your input.

Sounds like the timing was way off

I'd vote for cam timing, too. Maybe a tooth off.

If it's a good shop, they're gonna have to set it right and it won't be cheap.


Side note: This seems like the third or fourth incident of a plug blowing out due to bad threading. Wonder why.

--Paul

For the shop. As the shop should have to cower the expenses...

The plugs on aluminum head cannot be over torqued. That's why we read about them comong out.

Take that back to the shop. They messed that one up.

yeah they said they took valve cover off and retq'd everybolt and ehcekd valve and did a valve job, they fed it up, they refused to look at it, and i contacted corprate yamaha caz thats the shop i took iot to caz the honda shop are the ones who fed up the head and made the plug strip it in the first place, then finally they said theyd take the head 0off which they should of done in the first place being warrenty work, they said if its nothnig they did there gonna put my parts in a box and tell me to come get it i said hell no u guys arnt touching it again, when i picked up the bike they were cussing and stuff and told me my warrenty is gone when i leave and all that sstuff, im contacting the better business bureau and also gonna get an attorney and ram em inm the ass hard!!!!

Pretty much what greenville said.
The plugs can not be over torqued, they strip the head easily.
My previous owner stripped at least one nice and good.
Total bill for fixing all four plugs and getting them helicoiled was $360 bones.
Did a little research and getting them helicoiled is a pretty good idea.
The helicoil increases thread life and distributes thread pressure evenly, most threads carry most or all of the pressure on the first 2 threads leaving the remaining threads a bit useless. A helicoil pretty much fixes that and distributes pressure evenly throughout all threads.

Does putting in the helicoil require removing the head? Hard to imagine it wouldn't.

--Paul

Makes it a hella of alot easier. Thats for sure. lol