Left cylinder detonation?

[White97Banshee]

First off, my mods are:

 

Toomey T5's, stock carbs jetted 27.5 pilots 1.5 turns out 330 mains, k&n pods, vf2 reeds.

 

I took the 'shee to oregon for some dune riding this weekend and shee was running real strong for the first couple hours but after a few runs through the trails and treeshots it started taking a dump on me all of the suddon like it completely lost compression and wouldn't stay running. I took it home and today i tore it apart and found the left side piston has a hole in it and it looks like almost like a slab of concrete and the left side combustion chamber is destroyed. Now I know that I don't have any intake leaks and I know my jetting is 1 size too rich (I keep it that way so I don't have to rejet to ride where I live and at sea level). I run her at 40:1 on Klotz Supertechniplate. I think it's detonation but I run a stock head on 92 octane pump gas so I don't know why it would be detonating? The only thing I could think of was the gas I was running was a few months old but it WAS premix and I regularly shake it up and keep the fuel and oil mixed well. Could running old gas cause detonation? Another thing since I have the top end apart I was wondering what's a good amount of play to have in the crank? How much side-to-side motion should a stock crank have? I know too much/too little is a bad thing but since I'm already replacing the top end I want to see if I need to either pick up a new crank or get mine trued/welded while I got it apart. ONE last thing, I pulled the clutch case off and noticed a washer sitting in there and the idler gear between the clutch basket and the kicker gear is very loose on there. I know F.A.S.T makes replacement bushings for the gear as well as the circlip that holds it in place and the washer itself (mine is bent pretty badly) but is there a way to tell that just putting a new bushing in there will work? Thanks in advance and sorry for the essay!

 

Kyle

[crash&burn]

It could be from the old fuel i dont know... i would say there was an air leak some wear and by noticing what you write at the bottom above your post above your pic there you patched your intake with hi-temp silcone and gorilla glue i would say the air leak is there.... but i do know that where i buy my fuel from the guy there tells me when i dont use my fuel keep it in a metal can.... i was told it will last up to 12 to 18 months and being stored in a metal container and in a plastic container it will lose its octane leval over time quicker than in metal can

[White97Banshee]

The one I patched up was the right side cylinder and the left was neither side leaks I know this for sure. I'm just stumped as to why the left side blew and the right has no signs of detonation whatsoever. I know it's not from a lean condition as it would more than likely have siezed before burning a hole in the piston. My water pump is still fine and there are no problems with coolant flowing so detonation is the only thing I can think possible but I just can't see using 3 month old gas as a problem. I think you're right about the plastic container though because I don't use fuel stabilizer as I usually run my gas before it gets a chance to turn old. Hopefully someone can confirm my thoughts and address the other 2 questions.